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  • 1. Aalto, Juha
    et al.
    Riihimäki, Henri
    Meineri, Eric
    Hylander, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Luoto, Miska
    Revealing topoclimatic heterogeneity using meteorological station data2017Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 37, nr Suppl. 1, s. 544-556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Climate is a crucial driver of the distributions and activity of multiple biotic and abiotic processes, and thus high-quality and high-resolution climate data are often prerequisite in various environmental research. However, contemporary gridded climate products suffer critical problems mainly related to sub-optimal pixel size and lack of local topography-driven temperature heterogeneity. Here, by integrating meteorological station data, high-quality terrain information and multivariate modelling, we aim to explicitly demonstrate this deficiency. Monthly average temperatures (1981-2010) from Finland, Sweden and Norway were modelled using generalized additive modelling under (1) a conventional (i.e. considering geographical location, elevation and water cover) and (2) a topoclimatic framework (i.e. also accounting for solar radiation and cold-air pooling). The performance of the topoclimatic model was significantly higher than the conventional approach for most months, with bootstrapped mean R-2 for the topoclimatic model varying from 0.88 (January) to 0.95 (October). The estimated effect of solar radiation was evident during summer, while cold air pooling was identified to improve local temperature estimates in winter. The topoclimatic modelling exposed a substantial temperature heterogeneity within coarser landscape units (>5 degrees C/1 km(-2) in summer) thus unveiling a wide range of potential microclimatic conditions neglected by the conventional approach. Moreover, the topoclimatic model predictions revealed a pronounced asymmetry in average temperature conditions, causing isotherms during summer to differ several hundreds of metres in altitude between the equator and pole facing slopes. In contrast, cold-air pooling in sheltered landscapes lowered the winter temperatures ca. 1.1 degrees C/100m towards the local minimum altitude. Noteworthy, the analysis implies that conventional models produce biassed predictions of long-term average temperature conditions, with errors likely to be high at sites associated with complex topography.

  • 2. Abrahamczyk, S.
    et al.
    Kessler, M.
    Hanley, D.
    Karger, D. N.
    Mueller, M. P. J.
    Knauer, A. C.
    Keller, F.
    Schwerdtfeger, M.
    Humphreys, Aelys M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Imperial College London, UK.
    Pollinator adaptation and the evolution of floral nectar sugar composition2017Inngår i: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 30, nr 1, s. 112-127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A long-standing debate concerns whether nectar sugar composition evolves as an adaptation to pollinator dietary requirements or whether it is 'phylogenetically constrained'. Here, we use a modelling approach to evaluate the hypothesis that nectar sucrose proportion (NSP) is an adaptation to pollinators. We analyse similar to 2100 species of asterids, spanning several plant families and pollinator groups (PGs), and show that the hypothesis of adaptation cannot be rejected: NSP evolves towards two optimal values, high NSP for specialist-pollinated and low NSP for generalist-pollinated plants. However, the inferred adaptive process is weak, suggesting that adaptation to PG only provides a partial explanation for how nectar evolves. Additional factors are therefore needed to fully explain nectar evolution, and we suggest that future studies might incorporate floral shape and size and the abiotic environment into the analytical framework. Further, we show that NSP and PG evolution are correlated - in a manner dictated by pollinator behaviour. This contrasts with the view that a plant necessarily has to adapt its nectar composition to ensure pollination but rather suggests that pollinators adapt their foraging behaviour or dietary requirements to the nectar sugar composition presented by the plants. Finally, we document unexpectedly sucrose-poor nectar in some specialized nectarivorous bird-pollinated plants from the Old World, which might represent an overlooked form of pollinator deception. Thus, our broad study provides several new insights into how nectar evolves and we conclude by discussing why maintaining the conceptual dichotomy between adaptation and constraint might be unhelpful for advancing this field.

  • 3. Adam, Birgit
    et al.
    Klawonn, Isabell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Svedén, Jenny B.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Bergkvist, Johanna
    Nahar, Nurun
    Walve, Jakob
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Littmann, Sten
    Whitehouse, Martin J.
    Lavik, Gaute
    Kuypers, Marcel M. M.
    Ploug, Helle
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. University of Gothenburg, Sweden.
    N2-fixation, ammonium release and N-transfer to the microbial and classical food web within a plankton community2016Inngår i: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 10, nr 2, s. 450-459Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated the role of N2-fixation by the colony-forming cyanobacterium, Aphanizomenon spp., for the plankton community and N-budget of the N-limited Baltic Sea during summer by using stable isotope tracers combined with novel secondary ion mass spectrometry, conventional mass spectrometry and nutrient analysis. When incubated with 15N2Aphanizomenon spp. showed a strong 15N-enrichment implying substantial 15N2-fixation. Intriguingly, Aphanizomenon did not assimilate tracers of 15NH4+ from the surrounding water. These findings are in line with model calculations that confirmed a negligible N-source by diffusion-limited NH4+ fluxes to Aphanizomenon colonies at low bulk concentrations (<250 nm) as compared with N2-fixation within colonies. No N2-fixation was detected in autotrophic microorganisms <5 μm, which relied on NH4+uptake from the surrounding water. Aphanizomenon released about 50% of its newly fixed N2 as NH4+. However, NH4+ did not accumulate in the water but was transferred to heterotrophic and autotrophic microorganisms as well as to diatoms (Chaetoceros sp.) and copepods with a turnover time of ~5 h. We provide direct quantitative evidence that colony-formingAphanizomenon releases about half of its recently fixed N2 as NH4+, which is transferred to the prokaryotic and eukaryotic plankton forming the basis of the food web in the plankton community. Transfer of newly fixed nitrogen to diatoms and copepods furthermore implies a fast export to shallow sediments via fast-sinking fecal pellets and aggregates. Hence, N2-fixing colony-forming cyanobacteria can have profound impact on ecosystem productivity and biogeochemical processes at shorter time scales (hours to days) than previously thought.

  • 4.
    Ahlbeck Bergendahl, Ida
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Salvanes, Anne Gro V.
    Braithwaite, Victoria A.
    Determining the effects of duration and recency of exposure to environmental enrichment2016Inngår i: Applied Animal Behaviour Science, ISSN 0168-1591, E-ISSN 1872-9045, Vol. 176, s. 163-169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experience can help animals adapt their behaviour to fit the environment or conditions that they find themselves in. Understanding how and when experience affects behaviour is important for the animals we rear in captivity. This is particularly true when we rear animals with the intent of releasing them into the wild as part of population rehabilitation and conservation efforts. We investigated how exposure to a changing, more complex environment promotes behavioural development in juvenile trout. Four groups of fish were compared; (i) fish that were maintained without enrichment, (ii) fish that were exposed to an early period of enrichment, but were then returned to a plain environment, (iii) fish that were maintained in plain conditions, but were then exposed to enrichment towards the end of the rearing phase, (iv) a group that were kept in enriched conditions throughout the 12 week rearing period. We then assessed fish anxiety levels, their spatial learning ability, and the capacity of the fish to find their way through a barrier where different routes were presented across 4 different trials. Fish that experienced enriched conditions for the longest duration had superior spatial learning abilities, and they were better at finding the correct route to get past the barrier than fish from the remaining three treatments. Positive effects on behaviour were, however, also found in the fish that only experienced enrichment in the last part of the rearing period, compared to the control, or fish exposed to early enrichment. No effect of enrichment was found on levels of anxiety in any of the groups.

  • 5.
    Ahmed, Engy
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Parducci, Laura
    Unneberg, Per
    Ågren, Rasmus
    Schenk, Frederik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Rattray, Jayne E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Han, Lu
    Muschitiello, Francesco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper. Columbia University, USA.
    Pedersen, Mikkel W.
    Smittenberg, Rienk H.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Afrifa Yamoah, Kweku
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Slotte, Tanja
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Wohlfarth, Barbara
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Archaeal community changes in Lateglacial lake sediments: Evidence from ancient DNA2018Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 181, s. 19-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Lateglacial/early Holocene sediments from the ancient lake at Hasseldala Port, southern Sweden provide an important archive for the environmental and climatic shifts at the end of the last ice age and the transition into the present Interglacial. The existing multi-proxy data set highlights the complex interplay of physical and ecological changes in response to climatic shifts and lake status changes. Yet, it remains unclear how microorganisms, such as Archaea, which do not leave microscopic features in the sedimentary record, were affected by these climatic shifts. Here we present the metagenomic data set of Hasseldala Port with a special focus on the abundance and biodiversity of Archaea. This allows reconstructing for the first time the temporal succession of major Archaea groups between 13.9 and 10.8 ka BP by using ancient environmental DNA metagenomics and fossil archaeal cell membrane lipids. We then evaluate to which extent these findings reflect physical changes of the lake system, due to changes in lake-water summer temperature and seasonal lake-ice cover. We show that variations in archaeal composition and diversity were related to a variety of factors (e.g., changes in lake water temperature, duration of lake ice cover, rapid sediment infilling), which influenced bottom water conditions and the sediment-water interface. Methanogenic Archaea dominated during the Allerod and Younger Dryas pollen zones, when the ancient lake was likely stratified and anoxic for large parts of the year. The increase in archaeal diversity at the Younger Dryas/Holocene transition is explained by sediment infilling and formation of a mire/peatbog.

  • 6. Ahtiainen, Heini
    et al.
    Artell, Janne
    Elmgren, Ragnar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hasselström, Linus
    Håkansson, Cecilia
    Baltic Sea nutrient reductions - What should we aim for?2014Inngår i: Journal of Environmental Management, ISSN 0301-4797, E-ISSN 1095-8630, Vol. 145, s. 9-23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nutrient load reductions are needed to improve the state of the Baltic Sea, but it is still under debate how they should be implemented. In this paper, we use data from an environmental valuation study conducted in all nine Baltic Sea states to investigate public preferences of relevance to three of the involved decision-dimensions: First, the roles of nitrogen versus phosphorus reductions causing different eutrophication effects; second, the role of time the - lag between actions to reduce nutrient loads and perceived improvements; and third; the spatial dimension and the roles of actions targeting the coastal and open sea environment and different sub-basins. Our findings indicate that respondents view and value the Baltic Sea environment as a whole, and are not focussed only on their local sea area, or a particular aspect of water quality. We argue that public preferences concerning these three perspectives should be one of the factors guiding marine policy. This requires considering the entire range of eutrophication effects, in coastal and open sea areas, and including long-term and short-term measures.

  • 7. Alcamán, M. Estrella
    et al.
    Alcorta, Jaime
    Bergman, Birgitta
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Vásquez, Mónica
    Polz, Martin
    Díez, Beatriz
    Physiological and gene expression responses to nitrogen regimes and temperatures in Mastigocladus sp strain CHP1, a predominant thermotolerant cyanobacterium of hot springs2017Inngår i: Systematic and Applied Microbiology, ISSN 0723-2020, E-ISSN 1618-0984, Vol. 40, nr 2, s. 102-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cyanobacteria are widely distributed primary producers with significant implications for the global biogeochemical cycles of carbon and nitrogen. Diazotrophic cyanobacteria of subsection V (Order Stigonematales) are particularly ubiquitous in photoautotrophic microbial mats of hot springs. The Stigonematal cyanobacterium strain CHPI isolated from the Porcelana hot spring (Chile) was one of the major contributors of the new nitrogen through nitrogen fixation. Further morphological and genetic characterization verified that the strain CHP1 belongs to Stigonematales, and it formed a separate Glade together with other thermophiles of the genera Fischerella and Mastigocladus. Strain CHP1 fixed maximum N-2 in the light, independent of the temperature range. At 50 degrees C niJH gene transcripts showed high expression during the light period, whereas the nifH gene expression at 45 degrees C was arrhythmic. The strain displayed a high affinity for nitrate and a low tolerance for high ammonium concentrations, whereas the narB and glnA genes showed higher expression in light and at the beginning of the dark phase. It is proposed that Mastigocladus sp. strain CHPI would represent a good model for the study of subsection V thermophilic cyanobacteria, and for understanding the adaptations of these photoautotrophic organisms inhabiting microbial mats in hot springs globally.

  • 8. Alikas, Krista
    et al.
    Kratzer, Susanne
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Improved retrieval of Secchi depth for optically-complex waters using remote sensing data2017Inngår i: Ecological Indicators, ISSN 1470-160X, E-ISSN 1872-7034, Vol. 77, s. 218-227Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water transparency is one of the ecological indicators for describing water quality and the underwater light field which determines its productivity. In the European Water Framework Directive (WFD) as well as in the European Marine Strategy Framework Directive (MSFD) water transparency is used for ecological status classification of inland, coastal and open sea waters and it is regarded as an indicator for eutrophication in Baltic Sea management (HELCOM, 2007). We developed and compared different empirical and semi-analytical algorithms for lakes and coastal Nordic waters to retrieve Secchi depth (Z(SD)) from remote sensing data (MERIS, 300 m resolution).The algorithms were developed in water bodies with high coloured dissolved organic matter absorption (a(CNOM)(442) ranging 1.7-4.0 m(-1)), Chl a concentration (0.5-73 mg m(-3)) and total suspended matter (0.7-37.5 g m(-3)) and validated against an independent data set over inland and coastal waters (0.6 m < Z(SD) < 14.8 m). The results indicate that for empirical algorithms, using longer wavelengths in the visible spectrum as a reference band decreases the RMSE and increases the coefficient of determination (R-2). The accuracy increased (R-2 = 0.75, RMSE = 1.33 m, n = 134) when Z(SD) was retrieved via an empirical relationship between Z(SD) and K-d (490). The best agreement with in situ data was attained when Z(SD) was calculated via both the diffuse and the beam attenuation coefficient (R-2 = 0.89, RMSE = 0.77 m, n = 89). The results demonstrate that transparency can be retrieved with high accuracy over various optical water types by the means of ocean color remote sensing, improving both the spatial and temporal coverage. The satellite derived Z(SD) product could be therefore used as an additional source of information for WFD and MSFD reporting purposes.

  • 9. Alikas, Krista
    et al.
    Kratzer, Susanne
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Brockmann Consult GmbH, Geesthacht, Germany.
    Reinart, Anu
    Kauer, Tuuli
    Paavel, Birgot
    Robust remote sensing algorithms to derive the diffuse attenuation coefficient for lakes and coastal waters2015Inngår i: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, Vol. 13, nr 8, s. 402-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, empirical and semianalytical algorithms are developed and compared for optically complex waters to retrieve the diffuse attenuation coefficient of downwelling irradiance (Kd(lambda)) from satellite data. In the first approach, a band ratio algorithm was used. Various sets of MERIS band ratios were tested to achieve the best estimates for K-d(490) based on the in situ dataset which was measured in Nordic lakes (oligotrophic to eutrophic conditions). In the second approach, K-d(490) was expressed as a function of inherent optical properties which were retrieved from MERIS standard products. The algorithms from both approaches were tested against an independent data set and validated in optically complex coastal waters in the Baltic Sea and in Nordic lakes with high concentrations of coloured dissolved organic matter (0.3 < a(cdom)(442) m(-1) < 4.5), chlorophyll a (Chl a) (0.7< C-Chl a(mg m(-3))< 67.5) and total suspended matter (TSM) (0.5 < C-TSM(g m(-3)) < 26.4). MERIS-derived K-d(490) values showed reliable estimates in case of both methods. The results indicate that for band ratio algorithms, the root mean square error (RMSE) decreases and the coefficient of determination (R-2) increases when using longer wavelengths in the visible spectrum as a reference band. It was found that the best estimates were retrieved from MERIS data when using the ratio of R-rs(490)/R-rs(709) for coastal waters (K-d(490) < 2.5 m(-1)) and the ratio R-rs(560)/R-rs(709) for more turbid inland waters (Kd(490) > 2.5 m(-1)). As a result, a combined band ratio algorithm was developed, which provides a promising approach R-2 = 0.98, RMSE= 17%, N = 34, p < 0.05) for estimating K-d(490) over a wide range of values (0.3-6.1 m(-1)).

  • 10. Allen, Lisa Zeigler
    et al.
    McCrow, John P.
    Ininbergs, Karolina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Dupont, Christopher L.
    Badger, Jonathan H.
    Hoffman, Jeffery M.
    Ekman, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Allen, Andrew E.
    Bergman, Birgitta
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Venter, J. Craig
    The Baltic Sea Virome: Diversity and Transcriptional Activity of DNA and RNA Viruses2017Inngår i: mSystems, ISSN 2379-5077, Vol. 2, nr 1, artikkel-id UNSP e00125-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metagenomic and metatranscriptomic data were generated from size-fractionated samples from 11 sites within the Baltic Sea and adjacent marine waters of Kattegat and freshwater Lake Tornetrask in order to investigate the diversity, distribution, and transcriptional activity of virioplankton. Such a transect, spanning a salinity gradient from freshwater to the open sea, facilitated a broad genome-enabled investigation of natural as well as impacted aspects of Baltic Sea viral communities. Taxonomic signatures representative of phages within the widely distributed order Caudovirales were identified with enrichments in lesser-known families such as Podoviridae and Siphoviridae. The distribution of phage reported to infect diverse and ubiquitous heterotrophic bacteria (SAR11 clades) and cyanobacteria (Synechococcus sp.) displayed population-level shifts in diversity. Samples from higher-salinity conditions (>14 practical salinity units [PSU]) had increased abundances of viruses for picoeukaryotes, i.e., Ostreococcus. These data, combined with host diversity estimates, suggest viral modulation of diversity on the whole-community scale, as well as in specific prokaryotic and eukaryotic lineages. RNA libraries revealed single-stranded DNA (ssDNA) and RNA viral populations throughout the Baltic Sea, with ssDNA phage highly represented in Lake Tornetrask. Further, our data suggest relatively high transcriptional activity of fish viruses within diverse families known to have broad host ranges, such as Nodoviridae (RNA), Iridoviridae (DNA), and predicted zoonotic viruses that can cause ecological and economic damage as well as impact human health. IMPORTANCE Inferred virus-host relationships, community structures of ubiquitous ecologically relevant groups, and identification of transcriptionally active populations have been achieved with our Baltic Sea study. Further, these data, highlighting the transcriptional activity of viruses, represent one of the more powerful uses of omics concerning ecosystem health. The use of omics-related data to assess ecosystem health holds great promise for rapid and relatively inexpensive determination of perturbations and risk, explicitly with regard to viral assemblages, as no single marker gene is suitable for widespread taxonomic coverage.

  • 11.
    Alonso Aller, Elisa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Eklöf, Johan S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Gullström, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Kloiber, Ulrike
    Linderholm, Hans W.
    Nordlund, Lina M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Monitoring of a protected multi-specific tropical seagrass meadow reveals a pattern of decline and recoveryManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In a changing environment, there is an increasing interest to monitor ecosystems to understand their responses to environmental change. Seagrass meadows are highly important ecosystems, but at the same time they are under a constant threat from human activities, as well as climate impacts, and marked declines have been observed worldwide. Despite increasing efforts, monitoring of multi-specific tropical seagrass meadows is scarce, particularly in developing regions. Here we analysed data from the first 10 years of a monitoring programme in a marine protected area in Zanzibar (Tanzania) to assess temporal changes in seagrass cover and species composition and to detect potential drivers of change. The seagrass meadow experienced a strong gradual decline in seagrass cover and changes in species composition, followed by a period of recovery. However, the timing and length of these temporal patterns varied in space (between transects). Of the climate variables considered, cloud cover, temperature, storm occurrence, sunspot activity and the height of the diurnal low tide seemed to influence seagrass cover, although only to a small extent, suggesting that the monitored seagrass meadow may be influenced by other unmeasured factors. Considering our results, seagrass meadows seem to be highly dynamic at small spatial scales even in the absence of major local anthropogenic impacts. Further monitoring programmes should be developed in the region to gain a better understanding of seagrass temporal variability and causes of change.

  • 12.
    Alonso Aller, Elisa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Gullström, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Eveleens Maarse, Floriaan K. J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Gren, Michaela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Nordlund, Lina Mtwana
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. WIO CARE, Zanzibar, Tanzania.
    Jiddawi, Narriman
    Eklöf, Johan S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages2014Inngår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, nr 10, s. 2395-2405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Seagrass beds are highly important for tropical ecosystems by supporting abundant and diverse fish assemblages that form the basis for artisanal fisheries. Although a number of local- and regional-scale variables are known to influence the abundance, diversity and assemblage structure of seagrass-associated fish assemblages, few studies have evaluated the relative and joint (interacting) influences of variables, especially those acting at different scales. Here, we examined the relative importance of local- and regional-scale factors structuring seagrass-associated fish assemblages, using a field survey in six seagrass (Thalassodendron ciliatum) areas around Unguja Island (Zanzibar, Tanzania). Fish density and assemblage structure were mostly affected by two regional-scale variables; distance to coral reefs, which positively affected fish density, and level of human development, which negatively affected fish density. On the local scale, seagrass biomass had a positive (but weaker) influence on fish density. However, the positive effect of seagrass biomass decreased with increasing level of human development. In summary, our results highlight the importance of assessing how multiple local and regional variables, alone and together, influence fish communities, in order to improve management of seagrass ecosystems and their services.

  • 13.
    Alonso Aller, Elisa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Jiddawi, Narriman S.
    Eklöf, Johan S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Fishing weakens a positive link between herbivore abundance and plant growth in tropical seagrass bedsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Herbivory is a key process influencing the structure and function of both terrestrial and aquatic systems. In seagrass ecosystems, moderate levels of herbivory may stimulate plant growth, compensating for the loss of eaten tissue. However, the relationship between herbivory and seagrass growth can be influenced by an array of factors, such as seasonality, herbivore abundance, and presence of epiphytes, many of which can be directly or indirectly affected by human activities like fishing. Here, we used data from a multi-season field survey in fished and protected seagrass beds to assess how fishing and seasonality affect the link between herbivores, herbivory, and plant growth in seagrasses. Path analyses revealed an interactive effect of seasonality and protection. In protected seagrass beds, seasonally high herbivore abundance positively affected herbivory rates, which in turn enhanced seagrass growth. This link was however not apparent in seagrass beds subjected to fishing activities. At the same time, seasonality effects seemed stronger in fished areas, suggesting that in addition to weakening a positive herbivory-plant growth interaction, fishing increases temporal instability of ecosystems. Our results highlight the need for evaluating not only the direct effects of fisheries exploitation on fish populations, but also the potential indirect effects on ecosystems, to improve fisheries management.

  • 14.
    Alonso Aller, Elisa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Jiddawi, Narriman S.
    Eklöf, Johan S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities2017Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 8, artikkel-id e0183999Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Marine protected areas (MPAs) have been shown to increase long-term temporal stability of fish communities and enhance ecosystem resilience to anthropogenic disturbance. Yet, the potential ability of MPAs to buffer effects of environmental variability at shorter time scales remains widely unknown. In the tropics, the yearly monsoon cycle is a major natural force affecting marine organisms in tropical regions, and its timing and severity are predicted to change over the coming century, with potentially severe effects on marine organisms, ecosystems and ecosystem services. Here, we assessed the ability of MPAs to buffer effects of monsoon seasonality on seagrass-associated fish communities, using a field survey in two MPAs (no-take zones) and two unprotected (open-access) sites around Zanzibar (Tanzania). We assessed the temporal stability of fish density and community structure within and outside MPAs during three monsoon seasons in 2014-2015, and investigated several possible mechanisms that could regulate temporal stability. Our results show that MPAs did not affect fish density and diversity, but that juvenile fish densities were temporally more stable within MPAs. Second, fish community structure was more stable within MPAs for juvenile and adult fish, but not for subadult fish or the total fish community. Third, the observed effects may be due to a combination of direct and indirect (seagrass-mediated) effects of seasonality and, potentially, fluctuating fishing pressure outside MPAs. In summary, these MPAs may not have the ability to enhance fish density and diversity and to buffer effects of monsoon seasonality on the whole fish community. However, they may increase the temporal stability of certain groups, such as juvenile fish. Consequently, our results question whether MPAs play a general role in the maintenance of biodiversity and ecosystem functioning under changing environmental conditions in tropical seagrass fish communities.

  • 15. Alonzo, Frederic
    et al.
    Hertel-Aas, Turid
    Real, Almudena
    Lance, Emilie
    Garcia-Sanchez, Laurent
    Bradshaw, Clare
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Vives i Baffle, Jordi
    Oughton, Deborah H.
    Garnier-Laplace, Jacqueline
    Population modelling to compare chronic external radiotoxicity between individual and population endpoints in four taxonomic groups2016Inngår i: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 152, s. 46-59Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, we modelled population responses to chronic external gamma radiation in 12 laboratory species (including aquatic and soil invertebrates, fish and terrestrial mammals). Our aim was to compare radiosensitivity between individual and population endpoints and to examine how internationally proposed benchmarks for environmental radioprotection protected species against various risks at the population level. To do so, we used population matrix models, combining life history and chronic radiotoxicity data (derived from laboratory experiments and described in the literature and the FRED ERICA database) to simulate changes in population endpoints (net reproductive rate R-0, asymptotic population growth rate lambda, equilibrium population size N-eq) for a range of dose rates. Elasticity analyses of models showed that population responses differed depending on the affected individual endpoint (juvenile or adult survival, delay in maturity or reduction in fecundity), the considered population endpoint (R-0, lambda or N-eq) and the life history of the studied species. Among population endpoints, net reproductive rate R-0 showed the lowest EDR10 (effective dose rate inducing 10% effect) in all species, with values ranging from 26 mu Gy h(-1) in the mouse Mus musculus to 38,000 mu Gy h(-1) in the fish Oryzias latipes. For several species, EDR10 for population endpoints were lower than the lowest EDR10 for individual endpoints. Various population level risks, differing in severity for the population, were investigated. Population extinction (predicted when radiation effects caused population growth rate lambda to decrease below 1, indicating that no population growth in the long term) was predicted for dose rates ranging from 2700 mu Gy h(-1) in fish to 12,000 mu Gy h(-1) in soil invertebrates. A milder risk, that population growth rate lambda will be reduced by 10% of the reduction causing extinction, was predicted for dose rates ranging from 24 mu Gy h(-1) in mammals to 1800 mu Gy h(-1) in soil invertebrates. These predictions suggested that proposed reference benchmarks from the literature for different taxonomic groups protected all simulated species against population extinction. A generic reference benchmark of 10 mu Gy h(-1) protected all simulated species against 10% of the effect causing population extinction. Finally, a risk of pseudo-extinction was predicted from 2.0 mu Gy h(-1) in mammals to 970 mu Gy h(-1) in soil invertebrates, representing a slight but statistically significant population decline, the importance of which remains to be evaluated in natural settings.

  • 16. Amienl, Aldine R.
    et al.
    Johnston, Hereroa
    Chock, Taylor
    Dahlin, Paul
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Iglesias, Marta
    Layden, Michael
    Röttinger, Eric
    Martindale, Mark Q.
    A bipolar role of the transcription factor ERG for cnidarian germ layer formation and apical domain patterning2017Inngår i: Developmental Biology, ISSN 0012-1606, E-ISSN 1095-564X, Vol. 430, nr 2, s. 346-361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Germ layer formation and axial patterning are biological processes that are tightly linked during embryonic development of most metazoans. In addition to canonical WNT, it has been proposed that ERK-MAPK signaling is involved in specifying oral as well as aboral territories in cnidarians. However, the effector and the molecular mechanism underlying latter phenomenon is unknown. By screening for potential effectors of ERK-MAPK signaling in both domains, we identified a member of the ETS family of transcription factors, Nverg that is bipolarily expressed prior to gastrulation. We further describe the crucial role of NvERG for gastrulation, endomesoderm as well as apical domain formation. The molecular characterization of the obtained NvERG knock-down phenotype using previously described as well as novel potential downstream targets, provides evidence that a single transcription factor, NvERG, simultaneously controls expression of two different sets of downstream targets, leading to two different embryonic gene regulatory networks (GRNs) in opposite poles of the developing embryo. We also highlight the molecular interaction of cWNT and MEK/ERK/ERG signaling that provides novel insight into the embryonic axial organization of Nematostella, and show a cWNT repressive role of MEK/ERK/ERG signaling in segregating the endomesoderm in two sub-domains, while a common input of both pathways is required for proper apical domain formation. Taking together, we build the first blueprint for a global cnidarian embryonic GRN that is the foundation for additional gene specific studies addressing the evolution of embryonic and larval development.

  • 17. Andersson, Agneta
    et al.
    Höglander, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Karlsson, Chatarina
    Huseby, Siv
    Key role of phosphorus and nitrogen in regulating cyanobacterial community composition in the northern Baltic Sea2015Inngår i: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 164, s. 161-171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite cyanobacteria being a key phytoplankton group in the Baltic Sea, the factors governing their community structure are still poorly understood. Here, we studied the occurrence of the orders Chroococcales, Oscillatoriales and Nostocales, and potentially explanatory variables at five locations in the northern Baltic Sea from June September, 1998-2012. Cyanobacteria constituted 1-36% of the total phytoplankton biomass along the north south gradient. In the Bothnian Bay, Chroococcales and Oscillatoriales dominated the cyanobacterial community, whereas in the Bothnian Sea and northern Baltic Proper, Nostocales was the dominant group. The dominance of Chroococcales was coupled to low salinity and low total phosphorus, whereas Oscillatoriales correlated with high total nitrogen and low salinity. Nostocales correlated to high total phosphorus, inorganic phosphorus and salinity. Chroococcales showed an increase over time in the offshore Bothnian Bay, whereas Nostocales increased in the coastal Bothnian Sea and coastal Baltic Proper. The increase of Nostocales in the coastal Bothnian Sea was explained by a rise in total phosphorus and decrease in dissolved inorganic nitrogen compared to an increase of total nitrogen and phosphorus in the coastal Baltic Proper. No significant trends were observed in the cyanobacterial community in the offshore Bothnian Sea and the offshore northern Baltic Proper. We concluded that Chroococcales may be a useful indicator for increased phosphorus levels in waters with low phosphorus concentrations, whereas Nostocales could be used as a quality indicator for increasing phosphorus concentrations in waters with low inorganic N/P ratios (< 20), such as in the coastal Bothnian Sea and Baltic Proper.

  • 18. Andersson, Agneta
    et al.
    Meier, H. E. Markus
    Ripszam, Matyas
    Rowe, Owen
    Wikner, Johan
    Haglund, Peter
    Eilola, Kari
    Legrand, Catherine
    Figueroa, Daniela
    Paczkowska, Joanna
    Lindehoff, Elin
    Tysklind, Mats
    Elmgren, Ragnar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Projected future climate change and Baltic Sea ecosystem management2015Inngår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, s. S345-S356Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Climate change is likely to have large effects on the Baltic Sea ecosystem. Simulations indicate 2-4 degrees C warming and 50-80 % decrease in ice cover by 2100. Precipitation may increase similar to 30 % in the north, causing increased land runoff of allochthonous organic matter (AOM) and organic pollutants and decreased salinity. Coupled physical-biogeochemical models indicate that, in the south, bottom-water anoxia may spread, reducing cod recruitment and increasing sediment phosphorus release, thus promoting cyanobacterial blooms. In the north, heterotrophic bacteria will be favored by AOM, while phytoplankton production may be reduced. Extra trophic levels in the food web may increase energy losses and consequently reduce fish production. Future management of the Baltic Sea must consider the effects of climate change on the ecosystem dynamics and functions, as well as the effects of anthropogenic nutrient and pollutant load. Monitoring should have a holistic approach, encompassing both autotrophic (phytoplankton) and heterotrophic (e.g., bacterial) processes.

  • 19.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Plant patch structure influences plant fitness via antagonistic and mutualistic interactions but in different directions2016Inngår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 180, nr 4, s. 1175-1182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plant patch structure and environmental context can influence the outcome of antagonistic and mutualistic plant-insect interactions, leading to spatially variable fitness effects for plants. We investigated the effects of herbivory and pollen limitation on plant reproductive performance in 28 patches of the self-compatible perennial herb Scrophularia nodosa and assessed how such effects varied with plant patch size, plant density and tree cover. Both antagonistic and mutualistic interactions had strong effects on plant reproductive performance. Leaf feeding from herbivores reduced both fruit production and seed germination, and leaf herbivory increased with plant patch size. Experimentally hand-pollinated flowers produced more seeds than open-pollinated flowers, and pollen limitation was more severe in patches with fewer plants. Our study on S. nodosa is one of few which documents that plant patch structure influences the outcome of both antagonistic and mutualistic plant-insect interactions. The results thus provide an example of how variation in plant patch structure and environmental factors can lead to spatially variable fitness effects from mutualistic and antagonistic interactions.

  • 20.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Löfstedt, Christer
    Lund Univ, Dept Biol..
    Hambäck, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Insect density-plant density relationships: a modified view of insect responses to resource concentrations2013Inngår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 173, nr 4, s. 1333-1344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Habitat area is an important predictor of spatial variation in animal densities. However, the area often correlates with the quantity of resources within habitats, complicating our understanding of the factors shaping animal distributions. We addressed this problem by investigating densities of insect herbivores in habitat patches with a constant area but varying numbers of plants. Using a mathematical model, predictions of scale-dependent immigration and emigration rates for insects into patches with different densities of host plants were derived. Moreover, a field experiment was conducted where the scaling properties of odour-mediated attraction in relation to the number of odour sources were estimated, in order to derive a prediction of immigration rates of olfactory searchers. The theoretical model predicted that we should expect immigration rates of contact and visual searchers to be determined by patch area, with a steep scaling coefficient, mu = -1. The field experiment suggested that olfactory searchers should show a less steep scaling coefficient, with mu a parts per thousand -0.5. A parameter estimation and analysis of published data revealed a correspondence between observations and predictions, and density-variation among groups could largely be explained by search behaviour. Aphids showed scaling coefficients corresponding to the prediction for contact/visual searchers, whereas moths, flies and beetles corresponded to the prediction for olfactory searchers. As density responses varied considerably among groups, and variation could be explained by a certain trait, we conclude that a general theory of insect responses to habitat heterogeneity should be based on shared traits, rather than a general prediction for all species.

  • 21.
    Andersson, Petter
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Löfstedt, Christer
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    How insects sense olfactory patches: the spatial scaling of olfactory information2013Inngår i: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 122, nr 7, s. 1009-1016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When searching for resources in heterogeneous environments, animals must rely on their abilities to detect the resources via their sensory systems. However, variation in the strength of the sensory cue may be mediated by the physical size of the resource patch. Patch detection of insects are often predicted by the scaling of sensory cues to patch size, where visual cues has been proposed to scale proportional to the diameter of the patch. The scaling properties of olfactory cues are, however, virtually unknown. Here, we investigated scaling rules for olfactory information in a gradient of numbers of odour sources, relevant to odour-mediated attraction under field conditions. We recorded moth antennal responses to sex pheromones downwind from pheromone patches and estimated the slope in the scaling relationship between the effective length of the odour plumes and the number of odour sources. These measurements showed that the effective plume length increased proportional to the square root of the number of odour sources. The scaling relationship, as estimated in the field experiment, was then evaluated against field data of the slope in the relationship between trap catch and release rate of chemical attractants for a wide range of insects. This meta-analysis revealed an average slope largely consistent with the estimated scaling relationship between the effective plume length and the number of odour sources. This study is the first to estimate the scaling properties of olfactory cues empirically and has implications for understanding and predicting the spatial distributions of insects searching by means of olfactory cues in heterogeneous environments.

  • 22.
    Angeler, David G.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Swedish University of Agricultural Sciences, Sweden.
    Allen, Craig R.
    Garmestani, Ahjond S.
    Gunderson, Lance H.
    Hjerne, Olle
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Winder, Monika
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Quantifying the Adaptive Cycle2015Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 12, artikkel-id e0146053Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adaptive cycle was proposed as a conceptual model to portray patterns of change in complex systems. Despite the model having potential for elucidating change across systems, it has been used mainly as a metaphor, describing system dynamics qualitatively. We use a quantitative approach for testing premises (reorganisation, conservatism, adaptation) in the adaptive cycle, using Baltic Sea phytoplankton communities as an example of such complex system dynamics. Phytoplankton organizes in recurring spring and summer blooms, a well-established paradigm in planktology and succession theory, with characteristic temporal trajectories during blooms that may be consistent with adaptive cycle phases. We used long-term (1994-2011) data and multivariate analysis of community structure to assess key components of the adaptive cycle. Specifically, we tested predictions about: reorganisation: spring and summer blooms comprise distinct community states; conservatism: community trajectories during individual adaptive cycles are conservative; and adaptation: phytoplankton species during blooms change in the long term. All predictions were supported by our analyses. Results suggest that traditional ecological paradigms such as phytoplankton successional models have potential for moving the adaptive cycle from a metaphor to a framework that can improve our understanding how complex systems organize and reorganize following collapse. Quantifying reorganization, conservatism and adaptation provides opportunities to cope with the intricacies and uncertainties associated with fast ecological change, driven by shifting system controls. Ultimately, combining traditional ecological paradigms with heuristics of complex system dynamics using quantitative approaches may help refine ecological theory and improve our understanding of the resilience of ecosystems.

  • 23.
    Ango, Tola Gemechu
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kulturgeografiska institutionen.
    Börjeson, Lowe
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kulturgeografiska institutionen.
    Senbeta, Feyera
    Hylander, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Balancing Ecosystem Services and Disservices: Smallholder Farmers' Use and Management of Forest and Trees in an Agricultural Landscape in Southwestern Ethiopia2014Inngår i: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 19, nr 1, artikkel-id 30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Farmers' practices in the management of agricultural landscapes influence biodiversity with implications for livelihoods, ecosystem service provision, and biodiversity conservation. In this study, we examined how smallholding farmers in an agriculture-forest mosaic landscape in southwestern Ethiopia manage trees and forests with regard to a few selected ecosystem services and disservices that they highlighted as beneficial or problematic. Qualitative and quantitative data were collected from six villages, located both near and far from forest, using participatory field mapping and semistructured interviews, tree species inventory, focus group discussions, and observation. The study showed that farmers' management practices, i.e., the planting of trees on field boundaries amid their removal from inside arable fields, preservation of trees in semimanaged forest coffee, maintenance of patches of shade coffee fields in the agricultural landscape, and establishment of woodlots with exotic trees result in a restructuring of the forest-agriculture mosaic. In addition, the strategies farmers employed to mitigate crop damage by wild mammals such as baboons and bush pigs, e. g., migration and allocation of migrants on lands along forests, have contributed to a reduction in forest and tree cover in the agricultural landscape. Because farmers' management practices were overall geared toward mitigating the negative impact of disservices and to augment positive services, we conclude that it is important to operationalize ecosystem processes as both services and disservices in studies related to agricultural landscapes.

  • 24.
    Ango, Tola Gemechu
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kulturgeografiska institutionen.
    Hylander, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Börjeson, Lowe
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Kulturgeografiska institutionen.
    Drivers and patterns of forest cover change since the late 1950s in southwest Ethiopia: deforestation, agriculture expansion, and coffee productionManuskript (preprint) (Annet vitenskapelig)
  • 25. Ardehed, Angelica
    et al.
    Johansson, Daniel
    Schagerström, Ellen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Kautsky, Lena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Johannesson, Kerstin
    Pereyra, Ricardo T.
    Complex spatial clonal structure in the macroalgae Fucus radicans with both sexual and asexual recruitment2015Inngår i: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 5, nr 19, s. 4233-4245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In dioecious species with both sexual and asexual reproduction, the spatial distribution of individual clones affects the potential for sexual reproduction and local adaptation. The seaweed Fucus radicans, endemic to the Baltic Sea, has separate sexes, but new attached thalli may also form asexually. We mapped the spatial distribution of clones (multilocus genotypes, MLGs) over macrogeographic (>500km) and microgeographic (<100m) scales in the Baltic Sea to assess the relationship between clonal spatial structure, sexual recruitment, and the potential for natural selection. Sexual recruitment was predominant in some areas, while in others asexual recruitment dominated. Where clones of both sexes were locally intermingled, sexual recruitment was nevertheless low. In some highly clonal populations, the sex ratio was strongly skewed due to dominance of one or a few clones of the same sex. The two largest clones (one female and one male) were distributed over 100-550km of coast and accompanied by small and local MLGs formed by somatic mutations and differing by 1-2 mutations from the large clones. Rare sexual events, occasional long-distance migration, and somatic mutations contribute new genotypic variation potentially available to natural selection. However, dominance of a few very large (and presumably old) clones over extensive spatial and temporal scales suggested that either these have superior traits or natural selection has only been marginally involved in the structuring of genotypes.

  • 26. Ardehed, Angelica
    et al.
    Johansson, Daniel
    Sundqvist, Lisa
    Schagerström, Ellen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Zagrodzka, Zuzanna
    Kovaltchouk, Nikolaj A.
    Bergström, Lena
    Kautsky, Lena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Rafajlovic, Marina
    Pereyra, Ricardo T.
    Johannesson, Kerstin
    Divergence within and among Seaweed Siblings (Fucus vesiculosus and F. radicans) in the Baltic Sea2016Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, nr 8, artikkel-id e0161266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Closely related taxa provide significant case studies for understanding evolution of new species but may simultaneously challenge species identification and definition. In the Baltic Sea, two dominant and perennial brown algae share a very recent ancestry. Fucus vesiculosus invaded this recently formed postglacial sea 8000 years ago and shortly thereafter Fucus radicans diverged from this lineage as an endemic species. In the Baltic Sea both species reproduce sexually but also recruit fully fertile new individuals by asexual fragmentation. Earlier studies have shown local differences in morphology and genetics between the two taxa in the northern and western Bothnian Sea, and around the island of Saaremaa in Estonia, but geographic patterns seemin conflict with a single origin of F. radicans. To investigate the relationship between northern and Estonian distributions, we analysed the genetic variation using 9 microsatellite loci in populations from eastern Bothnian Sea, Archipelago Sea and the Gulf of Finland. These populations are located in between earlier studied populations. However, instead of bridging the disparate genetic gap between N-W Bothnian Sea and Estonia, as expected from a simple isolation-by-distance model, the new populations substantially increased overall genetic diversity and showed to be strongly divergent from the two earlier analysed regions, showing signs of additional distinct populations. Contrasting earlier findings of increased asexual recruitment in low salinity in the Bothnian Sea, we found high levels of sexual reproduction in some of the Gulf of Finland populations that inhabit extremely low salinity. The new data generated in this study supports the earlier conclusion of two reproductively isolated but very closely related species. However, the new results also add considerable genetic and morphological complexity within species. This makes species separation at geographic scales more demanding and suggests a need for more comprehensive approaches to further disentangle the intriguing relationship and history of the Baltic Sea fucoids.

  • 27. Astor, Tina
    et al.
    Strengbom, Joachim
    Berg, Matty P.
    Lenoir, Lisette
    Marteinsdottir, Bryndis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Bengtsson, Jan
    Underdispersion and overdispersion of traits in terrestrial snail communities on islands2014Inngår i: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 4, nr 11, s. 2090-2102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding and disentangling different processes underlying the assembly and diversity of communities remains a key challenge in ecology. Species can assemble into communities either randomly or due to deterministic processes. Deterministic assembly leads to species being more similar (underdispersed) or more different (overdispersed) in certain traits than would be expected by chance. However, the relative importance of those processes is not well understood for many organisms, including terrestrial invertebrates. Based on knowledge of a broad range of species traits, we tested for the presence of trait underdispersion (indicating dispersal or environmental filtering) and trait overdispersion (indicating niche partitioning) and their relative importance in explaining land snail community composition on lake islands. The analysis of community assembly was performed using a functional diversity index (Rao's quadratic entropy) in combination with a null model approach. Regression analysis with the effect sizes of the assembly tests and environmental variables gave information on the strength of under- and overdispersion along environmental gradients. Additionally, we examined the link between community weighted mean trait values and environmental variables using a CWM-RDA. We found both trait underdispersion and trait overdispersion, but underdispersion (eight traits) was more frequently detected than overdispersion (two traits). Underdispersion was related to four environmental variables (tree cover, habitat diversity, productivity of ground vegetation, and location on an esker ridge). Our results show clear evidence for underdispersion in traits driven by environmental filtering, but no clear evidence for dispersal filtering. We did not find evidence for overdispersion of traits due to diet or body size, but overdispersion in shell shape may indicate niche differentiation between snail species driven by small-scale habitat heterogeneity. The use of species traits enabled us to identify key traits involved in snail community assembly and to detect the simultaneous occurrence of trait underdispersion and overdispersion.

  • 28.
    Audusseau, Hélène
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Kolb, Gundula
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Janz, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Plant Fertilization Interacts with Life History: Variation in Stoichiometry and Performance in Nettle-Feeding Butterflies2015Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, nr 5, artikkel-id e0124616Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Variation in food stoichiometry affects individual performance and population dynamics, but it is also likely that species with different life histories should differ in their sensitivity to food stoichiometry. To address this question, we investigated the ability of the three nettle-feeding butterflies (Aglais urticae, Polygonia c-album, and Aglais io) to respond adaptively to induced variation in plant stoichiometry in terms of larval performance. We hypothesized that variation in larval performance between plant fertilization treatments should be functionally linked to species differences in host plant specificity. We found species-specific differences in larval performance between plant fertilization treatments that could not be explained by nutrient limitation. We showed a clear evidence of a positive correlation between food stoichiometry and development time to pupal stage and pupal mass in Aglais urticae. The other two species showed a more complex response. Our results partly supported our prediction that host plant specificity affects larval sensitivity to food stoichiometry. However, we suggest that most of the differences observed may instead be explained by differences in voltinism (number of generations per year). We believe that the potential of some species to respond adaptively to variation in plant nutrient content needs further attention in the face of increased eutrophication due to nutrient leakage from human activities.

  • 29.
    Austin, Åsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hedberg, Nils
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hellström, Micaela
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Acropora algal symbiont C3u; generalist or eutrophication specialist?Manuskript (preprint) (Annet vitenskapelig)
  • 30. Baeten, Lander
    et al.
    Warton, David I.
    Van Calster, Hans
    De Frenne, Pieter
    Verstraeten, Gorik
    Bonte, Dries
    Bernhardt-Roemermann, Markus
    Cornelis, Johnny
    Decocq, Guillaume
    Eriksson, Ove
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hedl, Radim
    Heinken, Thilo
    Hermy, Martin
    Hommel, Patrick
    Kirby, Keith
    Naaf, Tobias
    Petrik, Petr
    Walther, Gian-Reto
    Wulf, Monica
    Verheyen, Kris
    A model-based approach to studying changes in compositional heterogeneity2014Inngår i: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 5, nr 2, s. 156-164Artikkel i tidsskrift (Fagfellevurdert)
  • 31. Barraclough, Timothy G.
    et al.
    Humphreys, Aelys M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Imperial College London, UK.
    The evolutionary reality of species and higher taxa in plants: a survey of post-modern opinion and evidence2015Inngår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 207, nr 2, s. 291-296Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Species are normally considered to be the fundamental unit for understanding the evolution of biodiversity. Yet, in a survey of botanists in 1940, twice as many felt that plant genera were more natural units than plant species. Revisiting the survey, we found more people now regarded species as a more evolutionarily real unit, but a sizeable number still felt that genera were more evolutionarily real than species. Definitions of evolutionarily real' split into those based on shared evolutionary history and those based on shared evolutionary fate via ongoing evolutionary processes. We discuss recent work testing for shared evolutionary fate at the species and higher levels and present preliminary evidence for evolutionarily significant higher taxa in plants.

  • 32. Batista-Santos, Paula
    et al.
    Duro, Nuno
    Rodrigues, Ana P.
    Semedo, Jose N.
    Alves, Paula
    da Costa, Mario
    Graca, Ines
    Pais, Isabel P.
    Scotti-Campos, Paula
    Lidon, Fernando C.
    Leitao, Antonio E.
    Pawlowski, Katharina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Ribeiro-Barros, Ana I.
    Ramalho, Jose C.
    Is salt stress tolerance in Casuarina glauca Sieb. ex Spreng. associated with its nitrogen-fixing root-nodule symbiosis? An analysis at the photosynthetic level2015Inngår i: Plant physiology and biochemistry (Paris), ISSN 0981-9428, E-ISSN 1873-2690, Vol. 96, s. 97-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Casuarina glauca is an actinorhizal tree which establishes root-nodule symbiosis with N-2-fixing Frankia bacteria. This plant is commonly found in saline zones and is widely used to remediate marginal soils and prevent desertification. The nature of its ability to survive in extreme environments and the extent of Frankia contribution to stress tolerance remain unknown. Thus, we evaluated the ability of C. glauca to cope with salt stress and the influence of the symbiosis on this trait. To this end, we analysed the impact of salt on plant growth, mineral contents, water relations, photosynthetic-related parameters and nonstructural sugars in nodulated vs. non-nodulated plants. Although the effects on photosynthesis and stomatal conductance started to become measurable in the presence of 200 mM NaCl, photochemical (e.g., photosynthetic electron flow) and biochemical (e.g., activity of photosynthetic enzymes) parameters were only strongly impaired when NaCl levels reached 600 mM. These results indicate the maintenance of high tissue hydration under salt stress, probably associated with enhanced osmotic potential. Furthermore, the maintenance of photosynthetic assimilation potential (A(max)), together with the increase in the quantum yield of down-regulated energy dissipation of PSII (Y-NPQ), suggested a down-regulation of photosynthesis instead of photo-damaging effects. A comparison of the impact of increasing NaCl levels on the activities of photosynthetic (RubisCO and ribulose-5 phosphate kinase) and respiratory (pyruvate kinase and NADH-dependent malate dehydrogenase) enzymes vs. photosynthetic electron flow and fluorescence parameters, revealed that biochemical impairments are more limiting than photochemical damage. Altogether, these results indicate that, under controlled conditions, C glauca tolerates high NaCl levels and that this capacity is linked to photosynthetic adjustments.

  • 33. Bauer, Susanne
    et al.
    Blomqvist, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Ingri, Johan
    Distribution of dissolved and suspended particulate molybdenum, vanadium, and tungsten in the Baltic Sea2017Inngår i: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 196, s. 135-147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In natural waters, dissolved oxyanions often dominate over the particle-bound element fraction. Still, the scavenging of oxyanions by suspended particles might contribute significantly to their dynamic cycling and distribution. To investigate how oxyanions are affected by manganese (Mn) redox cycling, detailed depth profiles across the pelagic redox zone at the Landsort Deep, Baltic Sea, were collected for molybdenum (Mo), vanadium (V), and tungsten (W), for both dissolved (< 0.22 mu m) and suspended particulate (> 0.22 mu m) fractions. All three oxyanions show a non-conservative behavior in the stratified Landsort Deep. Strong linear correlations with Mn in the particulate fraction in the redox zone of the Landsort Deep suggest that Mn redox cycling influences their distribution. In the dissolved fraction, Mo, V, and W exhibited rather different behavior. Molybdenum was depleted below the redox zone, while V was depleted only within the redox zone. Tungsten concentrations increased within the redox zone, being three times higher in the sulfidic zone than in the surface water. Unlike Mo, W shows no tendency for adsorption or co-precipitation under the prevailing weak sulfidic conditions in the deep water of the Landsort Deep and is, therefore, not exported to the underlying sediment. The Landsort Deep data were compared with data from the northern Baltic Sea (Bothnian Bay, Kalix River and Rane River estuaries), where particulate iron (Fe) occurs in high abundance. The particulate fractions of Mo, V, and W decreased during mixing in these estuaries. Vanadium showed the most drastic reduction, with a decrease in dissolved and particulate fractions, indicating that different processes influence the distribution of these oxyanions.

  • 34. Bay, Guillaume
    et al.
    Nahar, Nurun
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Oubre, Matthieu
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Whitehouse, Martin J.
    Wardle, David A.
    Zackrisson, Olle
    Nilsson, Marie-Charlotte
    Rasmussen, Ulla
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Boreal feather mosses secrete chemical signals to gain nitrogen2013Inngår i: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 200, nr 1, s. 54-60Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanistic basis of feather moss-cyanobacteria associations, a main driver of nitrogen (N) input into boreal forests, remains unknown. Here, we studied colonization by Nostoc sp. on two feather mosses that form these associations (Pleurozium schreberi and Hylocomium splendens) and two acrocarpous mosses that do not (Dicranum polysetum and Polytrichum commune). We also determined how N availability and moss reproductive stage affects colonization, and measured N transfer from cyanobacteria to mosses. The ability of mosses to induce differentiation of cyanobacterial hormogonia, and of hormogonia to then colonize mosses and re-establish a functional symbiosis was determined through microcosm experiments, microscopy and acetylene reduction assays. Nitrogen transfer between cyanobacteria and Pleurozium schreberi was monitored by secondary ion mass spectrometry (SIMS). All mosses induced hormogonia differentiation but only feather mosses were subsequently colonized. Colonization on Pleurozium schreberi was enhanced during the moss reproductive phase but impaired by elevated N. Transfer of N from cyanobacteria to their host moss was observed. Our results reveal that feather mosses likely secrete species-specific chemo-attractants when N-limited, which guide cyanobacteria towards them and from which they gain N. We conclude that this signalling is regulated by N demands of mosses, and serves as a control of N input into boreal forests.

  • 35.
    Belivanov, Yordan K.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hambäck, Peter A.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    The time scale of isotope signals in spiders: molting the remains of a previous diet2015Inngår i: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 156, nr 3, s. 271-278Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stable isotope analysis (SIA) has emerged as an important tool for understanding consumer diets and diet shifts. However, although the general idea behind SIA is clear, the interpretation of data is often fraught with problems because tissue turnover and fractionations are not known. We investigated shifts in stable isotope composition of spiders following a diet shift, using mealworms fed either maize (C4) or wheat (C3) flour. Mealworms had different carbon isotope composition depending on their diet and this difference was reflected in spider body parts. In the experiment, we first fed the spiders on a diet of either maize-fed or wheat-fed mealworms and then switched diet at the time of the second molt. Spiders were then sampled repeatedly until the next molt. We sampled both legs and abdomens, as these are presumed to have different turnover of tissue, and also molt remains were sampled when this was relevant. The data indicated that the spider legs had a turnover of about 20days, whereas the spider abdomens had a turnover of about 8days. Molt remains had the slowest turnover and reflected the diet at the previous molt, when the exoskeleton was formed. Both these observations indicate that SIA may be successfully used for elucidating diet shifts. More problematic was the fact that fractionation of carbon isotope ratios varied with body parts and diets. When spiders were fed maize-mealworms then the fractionation was larger for abdomens, but when the spiders were fed wheat-mealworms then the fractionation was larger for legs. The mechanisms underlying this pattern are unclear and deserve further attention.

  • 36.
    Beltrán-Abaunza, José M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Remote sensing in optically complex waters: water quality assessment using MERIS data2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This PhD study focusses on the use of MEdium Resolution Imaging Spectrometer (MERIS) data for reliable and quantitative water-quality assessment of optically-complex waters (lake, brackish and coastal waters). The thesis is divided into two parts: A. intercalibration of reflectance measurements in different optically-complex water bodies (Paper I), and validation of various satellite processing algorithms for the coastal zone (Paper II). B. Applications: the use of MERIS data in integrated coastal zone management mostly using Himmerfjärden bay as an example.

    Himmerfjärden bay is one of the most frequently monitored coastal areas in the world and it is also the recipient of a large urban sewage treatment plant, where a number of full-scale nutrient management experiments have been conducted to evaluate the ecological changes due to changes in nutrient schemes in the sewage plant.

    Paper I describes the development and assessment of a new hyperspectral handheld radiometer for in situ sampling and validation of remote sensing reflectance.  The instrument is assessed in comparison with readily available radiometers that are commonly used in validation.

    Paper II has a focus on the validation of level 2 reflectance and water products derived from MERIS data. It highlights the importance of calibration and validation activities, and the current accuracy and limitations of satellite products in the coastal zone.  Bio-optical in situ data is highlighted as one of the key components for assessing the reliability of current and future satellite missions. Besides suspended particulate matter (SPM), the standard MERIS products have shown to be insufficient to assure data quality retrieval for Baltic Sea waters. Alternative processors and methods such as those assessed and developed in this thesis therefore will have to be put in place in order to secure the success of future operational missions, such as Sentinel-3.

    The two presented manuscripts in the applied part B of the thesis (paper III and IV), showed examples on the combined use of in situ measurements with optical remote sensing to support water quality monitoring programs by using turbidity and suspended particulate matter as coastal indicators (manuscript III). The article also provides  a new turbidity algorithm for the Baltic Sea and a robust and cost-efficient method for research and management.  A novel approach to improve the quality of the satellite-derived products in the coastal zone was demonstrated in manuscript IV. The analysis included, the correction for adjacency effects from land and an improved pixel quality screening.  The thesis provides the first detailed spatio-temporal description of the evolution of phytoplankton blooms in Himmerfjärden bay  using quality-assured MERIS data, thus forwarding our understanding of ecological processes in in Swedish coastal waters.

    It must be noted that monitoring from space is not a trivial matter in these optically-complex waters dominated by the absorption of coloured dissolved organic matter (CDOM). These types of coastal waters are especially challenging for quantitative assessment from space due to their low reflectance.  Papers III and IV thus also provide tools for a more versatile use in other coastal waters that are not as optically-complex as the highly absorbing Baltic Sea waters. The benefits of the increased spatial-temporal data coverage by optical remote sensing were presented, and also compared to in situ sampling methods (using chlorophyll-a as indicator).

  • 37.
    Beltrán-Abaunza, José M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Uncertainty measurements and validation of ocean colour data in optically complex waters2013Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis addresses validation activities associated with the use of in situ and satellite-based radiometers to assess water quality parameters, such as chlorophyll-a (Chl-a), total suspended matter (TSM) and coloured dissolved organic matter (CDOM- also known as yellow substances, YEL) in CDOM-dominated waters. In paper I, an inter-comparison of in situ radiometers is presented. Here, a new hand-held radiometer, the Water Insight Spectrometer (WISP-3) was tested and evaluated for routine water monitoring against other common radiometers used for validation. The WISP-3 measures the reflectance at the surface, and thus also works in shallow depths. The WISP-3 is designed for validation in places where other radiometers are difficult to deploy. As it is hyperspectral it can be used to develop in-water algorithms for the retrieval of water-quality information. In paper II, satellite data from the 3rd reprocessing archives of the MEdium Resolution Imaging Spectrometer (MERIS) sensor on board of ENVISAT is evaluated. MERIS level 2 reflectance and water products are assessed against in situ data. This assessment is required in order to ensure the reliability of  monitoring systems based on MERIS data such as the Swedish coastal and lake monitoring system www.vattenkvalitet.se. The evaluation of reflectance data is based on a pair-wise comparison of the standard MEGS processor and three coastal processors that are provided as source free plug-ins for the VISAT BEAM software; all pairs are compared to data measured in situ. The derived water products are evaluated both on a pair-wise comparison of processors as well as on an individual comparison of some processors to sea-truthing data. The studied processors improved the retrievals of MERIS reflectance when used the latest MERIS FR 3rd reprocessing, equalized and “smile” corrected and a land adjacency effects were corrected using the improved contrast between ocean and land (ICOL). The blue spectral bands remain problematic for all processors. Chlorophyll was retrieved best using FUB with an overestimation between 18% - 26.5% (MNB) dependent on the compared pairs. At low chlorophyll < 2.5 mg m-3, random errors dominates the retrievals of MEGS. MEGS showed lower bias and random errors when deriving suspended particulate matter (SPM) with an overestimation in the range 8-16% (MNB). All processors failed to retrieve CDOM correctly, but FUB could at least resolve variations in CDOM, however with a systematic underestimation that may be corrected for by using a local correction factor . MEGS has shown already potential to be used as operational processor in the Himmerfjärden bay and adjacent areas, but it requires further improvement of the atmospheric correction for the blue bands and better definition at relatively low chlorophyll concentrations in presence of CDOM.

  • 38.
    Beltrán-Abaunza, José M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Kratzer, Susanne
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Brockmann, C.
    Evaluation of MERIS products from Baltic Sea coastal waters rich in CDOM2014Inngår i: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 10, nr 3, s. 377-396Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, retrievals of the medium resolution imaging spectrometer (MERIS) reflectances and water quality products using four different coastal processing algorithms freely available are assessed by comparison against sea-truthing data. The study is based on a pair-wise comparison using processor-dependent quality flags for the retrieval of valid common macro-pixels. This assessment is required in order to ensure the reliability of monitoring systems based on MERIS data, such as the Swedish coastal and lake monitoring system (http://vattenkvalitet.se). The results show that the pre-processing with the Improved Contrast between Ocean and Land (ICOL) processor, correcting for adjacency effects, improves the retrieval of spectral reflectance for all processors. Therefore, it is recommended that the ICOL processor should be applied when Baltic coastal waters are investigated. Chlorophyll was retrieved best using the FUB (Free University of Berlin) processing algorithm, although overestimations in the range 18-26.5 %, dependent on the compared pairs, were obtained. At low chlorophyll concentrations (< 2.5 mg m(-3)), data dispersion dominated in the retrievals with the MEGS (MERIS ground segment processor) processor. The lowest bias and data dispersion were obtained with MEGS for suspended particulate matter, for which overestimations in the range of 8-16% were found. Only the FUB retrieved CDOM (coloured dissolved organic matter) correlate with in situ values. However, a large systematic underestimation appears in the estimates that nevertheless may be corrected for by using a local correction factor. The MEGS has the potential to be used as an operational processing algorithm for the Himmerfjarden bay and adjacent areas, but it requires further improvement of the atmospheric correction for the blue bands and better definition at relatively low chlorophyll concentrations in the presence of high CDOM attenuation.

  • 39.
    Beltrán-Abaunza, José M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Kratzer, Susanne
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hoglander, Helena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Using MERIS data to assess the spatial and temporal variability of phytoplankton in coastal areas2017Inngår i: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 38, nr 7, s. 2004-2028Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study aims to highlight how satellite data can be used for an improved understanding of ecological processes in a narrow coastal bay. The usefulness of the Medium Resolution Imaging Spectrometer (MERIS) data (2003-2011) as a complement to the in situ monitoring in Himmerferdenn (HF) bay is used as an example that can also be applied to other coastal areas. HF bay is one of the most frequently monitored coastal areas in the world, allowing for a rigorous comparison between satellites and ship-based monitoring data. MERIS data was used for the integration of chlorophyll-a (chl-a) over each waterbody in the HF area, following the national waterbody classification by the Swedish Meteorological and Hydrological Institute (SMHI). Chl-a anomaly maps were produced for the bay and its adjacent areas. The maps could be used to show events with high chl-a, both with natural causes (e.g. a Prymnesium polylepis bloom observed in summer 2008) and of anthropogenic causes (e.g. failure in the local sewage treatment plant resulting in a strong spring bloom in 2006). Anomaly maps thereby allow to scan larger coastal stretches to discriminate areas that may require additional sampling by ship, or to identify areas that do not differ much from the median value of the MERIS time series.

  • 40.
    Ben Mustapha, Selima
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Université de Sherbrooke, Canada; Institut Maurice-Lamontagne, Canada.
    Larouche, Pierre
    Dubois, Jean-Marie
    Spatial and temporal variability of sea-surface temperature fronts in the coastal Beaufort Sea2016Inngår i: Continental Shelf Research, ISSN 0278-4343, E-ISSN 1873-6955, Vol. 124, s. 134-141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An analysis of 11 years of sea surface temperatures images allowed the determination of the frontal occurrence probability in the southeastern Beaufort Sea using the single-image edge detection method. Results showed that, as the season progresses, fronts become more detectable due to solar heating of the surface layer. Some recurrent features can be identified in the summer time frontal climatology such as the Mackenzie River plume front, the Cape Bathurst front, the Mackenzie Trough front and the Amundsen Gulf front. These areas may be playing an important role in the biological processes acting as drivers to local enhanced biological productivity.

  • 41.
    Bengtson, Annika
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Systematics and biogeography of the South African Metalasia clade (Asteraceae-Gnaphalieae)2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The Metalasia clade (Asteraceae–Gnaphalieae) consisting of the genera Metalasia, Atrichantha, Calotesta, Dolichothrix, Hydroidea, Lachnospermum, Phaenocoma, and Planea is endemic to South Africa with a main distribution within the Cape Floristic Region (CFR), a region known for its remarkable botanical diversity.

    The monophyly of the Metalasia clade, the relationships of its genera, and the circumscription of these as well as their position within the tribe Gnaphalieae is investigated using molecular data. The study confirms the Metalasia clade to be a monophyletic group, untangling the relationships between the included genera.

    Five new Metalasia species have been described since the latest revision of the genus, three of which are described in the present work. An updated key to all 57 species of the genus is also provided.

    A phylogenetic study of the genus Metalasia, including all 57 species, based on a combination of morphological and molecular data shows that Metalasia consists of two sister clades, Clade A and Clade B, morphologically separated by the papillose cypselas of Clade A. Metalasia is, however, not supported as monophyletic, and Lachnospermum is placed together with the Metalasia species of Clade B. Further, the monotypic Planea, originally described as Metalasia schlechteri, is placed well within Clade B.

    A biogeographical study reveals Metalasia to have evolved in the CFR around 6.9 Ma. Ancestral area estimations present a possible scenario for the radiation of Metalasia and show a difference between Clade A and B, correlated to the different rainfall regimes of southern Africa. The results show that Clade B began to diversify around 6.4 Ma in the winter rainfall area, whereas the diversification of the Clade A crown group, which is estimated to only 3.3 Ma, was initiated in the all-year rainfall area.

  • 42.
    Bengtson, Annika
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Anderberg, Arne A.
    Karis, Per Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Phylogeny and evolution of the South African genus Metalasia (Asteraceae-Gnaphalieae) inferred from molecular and morphological data2014Inngår i: Botanical journal of the Linnean Society, ISSN 0024-4074, E-ISSN 1095-8339, Vol. 174, nr 2, s. 173-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metalasia is a genus in tribe Gnaphalieae (Asteraceae), endemic to South Africa and with its main distribution in the Cape Floristic Region. The genus comprises 57 species and, with a number of closely related genera, it constitutes the Metalasia clade'. A species-level phylogenetic analysis is presented, based on DNA sequences from two nuclear (internal and external transcribed spacer: ITS, ETS) and two plastid (psbA-trnH, trnL-trnF) regions together with morphological data. Analyses combining molecular and morphological data attempt not only to resolve species interrelationships, but also to detect patterns in character evolution. Phylogenetic analyses corroborate our earlier study and demonstrate that Metalasia is formed of two equally sized, well-supported sister groups, one of which is characterized by papillose cypselas. The results differ greatly from earlier hypotheses based on morphology alone, as few morphological characters support the phylogenetic patterns obtained. The two clades of Metalasia do, however, appear to differ in distribution, corresponding to the different rainfall regimes of South Africa. Analyses show a few taxa to be problematic; one example is the widely distributed M.densa which appears to be an intricate species complex.

  • 43. Bengtson, Annika
    et al.
    Englund, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Swedish Museum of Natural History, Sweden.
    Pruski, John F.
    Anderberg, Arne A.
    Phylogeny of the Athroismeae (Asteraceae), with a new circumscription of the tribe2017Inngår i: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 66, nr 2, s. 408-420Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Athroismeae is a small tribe of the Asteraceae-Asteroideae, the members of which show considerable variation in morphology. A molecular phylogenetic study of the tribe is presented for the first time, based on plastid (ndhF, trnH-psbA, trnL-trnF) and nuclear data (ETS, ITS). The phylogenetic relationships between the different genera within Athroismeae are discussed, and in addition, three unispecific genera: Anisochaeta, Artemisiopsis and Symphyllocarpus as well as Duhaldea (Inula) stuhlmannii, all earlier placed in other tribes, are here shown to belong within Athroismeae. Symphyllocarpus is sister to Centipeda and the earlier Symphyllocarpinae includes Centipedinae in synonymy. Furthermore, Cardosoa and Philyrophyllum are found to be integrated within Anisopappus and their generic status cannot be maintained. An outline of an amended circumscription of the Athroismeae is presented, with three new combinations and a description of the new subtribe Lowryanthinae.

  • 44.
    Bengtson, Annika
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Nylinder, Stephan
    Karis, Per Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Anderberg, Arne A.
    Evolution and diversification related to rainfall regimes: diversification patterns in the South African genus Metalasia (Asteraceae-Gnaphalieae)2015Inngår i: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 42, nr 1, s. 121-131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    AimThe Cape region is known for its exceptional species richness, although much remains unknown regarding the appearance of the modern Cape flora. One explanation is that floral diversification was influenced by the establishment of winter rainfall/summer arid conditions hypothesized to have occurred towards the end of the Miocene. We studied the evolution and diversification of the plant genus Metalasia (Asteraceae-Gnaphalieae), with the aim of testing whether radiation patterns may have been influenced by the climatic changes. LocationSouth Africa, with emphasis on the south-west. MethodsThe radiation of Metalasia was investigated using two approaches: a species diffusion approach, which estimated the ancestral areas by means of a relaxed random walk while sampling from extant distributions; and a discrete approach, in which distributions were defined according to the phytogeographical centres of the Cape region. Secondarily derived clock rates from an earlier Gnaphalieae study were used for calibration purposes. ResultsOur analyses date Metalasia to approximately 6.9Ma, after the Miocene-Pliocene boundary and the establishment of the winter rainfall/summer arid conditions. Metalasia consists of two sister clades: Clade A and Clade B. Clade B, which is endemic to the winter rainfall area, is estimated to have diversified c. 6.4Ma, whereas Clade A, with a main distribution in the all-year rainfall area, is considerably younger, with a crown group age estimated to 3.3Ma. Diversification rates suggest an early rapid speciation, with rates decreasing through time both for Metalasia and for clades A and B separately. Ancestral area estimations show a possible scenario for the radiation of Metalasia to its current diversity and distribution, with no conflict between results inferred from diffusion or discrete methods. Main conclusionsThe diversification of Metalasia is estimated to have begun after the establishment of the winter rainfall/summer arid conditions, consistent with its radiation having been influenced by changes in the climatic regime.

  • 45. Beresford, Nicholas A.
    et al.
    Wood, Michael D.
    Vives i Batlle, Jordi
    Yankovich, Tamara L.
    Bradshaw, Clare
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Willey, Neil
    Making the most of what we have: application of extrapolation approaches in radioecological wildlife transfer models2016Inngår i: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 151, s. 373-386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We will never have data to populate all of the potential radioecological modelling parameters required for wildlife assessments. Therefore, we need robust extrapolation approaches which allow us to make best use of our available knowledge. This paper reviews and, in some cases, develops, tests and validates some of the suggested extrapolation approaches. The concentration ratio (CRproduct-diet or CRwo-diet) is shown to be a generic (trans-species) parameter which should enable the more abundant data for farm animals to be applied to wild species. An allometric model for predicting the biological half-life of radionuclides in vertebrates is further tested and generally shown to perform acceptably. However, to fully exploit allometry we need to understand why some elements do not scale to expected values. For aquatic ecosystems, the relationship between log10(a) (a parameter from the allometric relationship for the organism-water concentration ratio) and log(K-d) presents a potential opportunity to estimate concentration ratios using K-d values. An alternative approach to the CRwo-media model proposed for estimating the transfer of radionuclides to freshwater fish is used to satisfactorily predict activity concentrations in fish of different species from three lakes. We recommend that this approach (REML modelling) be further investigated and developed for other radionuclides and across a wider range of organisms and ecosystems. Ecological stoichiometry shows potential as an extrapolation method in radioecology, either from one element to another or from one species to another. Although some of the approaches considered require further development and testing, we demonstrate the potential to significantly improve predictions of radionuclide transfer to wildlife by making better use of available data.

  • 46.
    Berg, Carlo
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik. Stockholms universitet, Science for Life Laboratory (SciLifeLab). Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Germany.
    Vandieken, Verona
    Thamdrup, Bo
    Juergens, Klaus
    Significance of archaeal nitrification in hypoxic waters of the Baltic Sea2015Inngår i: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 9, nr 6, s. 1319-1332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ammonia-oxidizing archaea (AOA) of the phylum Thaumarchaeota are widespread, and their abundance in many terrestrial and aquatic ecosystems suggests a prominent role in nitrification. AOA also occur in high numbers in oxygen-deficient marine environments, such as the pelagic redox gradients of the central Baltic Sea; however, data on archaeal nitrification rates are scarce and little is known about the factors, for example sulfide, that regulate nitrification in this system. In the present work, we assessed the contribution of AOA to ammonia oxidation rates in Baltic deep basins and elucidated the impact of sulfide on this process. Rate measurements with N-15-labeled ammonium, CO2 dark fixation measurements and quantification of AOA by catalyzed reporter deposition-fluorescence in situ hybridization revealed that among the three investigated sites the highest potential nitrification rates (122-884 nmol l(-1) per day) were measured within gradients of decreasing oxygen, where thaumarchaeotal abundance was maximal (2.5-6.9 x 10(5) cells per ml) and CO2 fixation elevated. In the presence of the archaeal-specific inhibitor GC7, nitrification was reduced by 86-100%, confirming the assumed dominance of AOA in this process. In samples spiked with sulfide at concentrations similar to those of in situ conditions, nitrification activity was inhibited but persisted at reduced rates. This result together with the substantial nitrification potential detected in sulfidic waters suggests the tolerance of AOA to periodic mixing of anoxic and sulfidic waters. It begs the question of whether the globally distributed Thaumarchaeota respond similarly in other stratified water columns or whether the observed robustness against sulfide is a specific feature of the thaumarchaeotal subcluster present in the Baltic Deeps.

  • 47.
    Bergendahl, I. Ahlbeck
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Holliland, Per Benjamin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Hansson, Sture
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Karlöf, Oliver
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Feeding range of age 1+year Eurasian perch Perca fluviatilis in the Baltic Sea2017Inngår i: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 90, nr 5, s. 2060-2072Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the widespread Eurasian perch Perca fluviatilis as a model organism, feeding ranges were investigated using stable-isotope ratios (N-15 and C-13) and body condition. Differences were found between closely located sampling sites in a littoral area without obvious migration barriers, indicating that individual fish had small feeding ranges. Body condition differences between sampled stations were consistent over 4 years. Such sedentary behaviour is important to consider in, e.g. fisheries management and environmental monitoring, as local catch regulations may be meaningful or geographic stability in sampling locations may reduce noise in data.

  • 48.
    Bergqvist, Claes
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Arsenic accumulation in plants for food and phytoremediation: Influence by external factors2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Arsenic (As) appears in the environment as various As species, which may vary in plant uptake and toxicity. Moreover, As exposure may vary between habitat due to availability and speciation, both of which are influenced by redox potential. To decrease As uptake, addition of silicate may be a tool.

    The aim of the study was to investigate how the external factors As availability, plant habitats, silicon and oxygen level, influenced the accumulation and speciation of As in plants for food and phytoremediation in a temperate region. The external factors were chosen due to their previously showed influence on As in plants.

    The risks with dietary As was investigated by plant As accumulation and speciation in carrot, lettuce and spinach grown in alum shale and glassworks soils, and by the influence of silicon on As accumulation in lettuce in hydroponics. Suitable plants for As phytoremediation was investigated by analysing plants from various habitats, and by the O2 influence on phytofiltration.

    The results showed that vegetables accumulated more As in soils with higher As extractability, and the As extractability in the rhizosphere was higher than in bulk soil. Also, the As concentration in lettuce was higher in hydroponics than in soil, but silicon reduced the accumulation of As in lettuce in hydroponics. Also, the more toxic inorganic As were the main As species detected in vegetables, compared with the less toxic organic As. For phytoremediation, the results showed a low As accumulation in emergent and terrestrial plants. Submerged plants had had a higher shoot As concentration. In general, the habitat had a major influence on the As accumulation in plants. The results also showed that the As accumulation properties in Elodea canadensis was reduced at higher O2.

    In conclusion, consumption of vegetables cultivated in As polluted soils can result in an elevated intake of inorganic As, and E. canadensis is a promising candidate for As phytofiltration in a temperate region.

  • 49.
    Bergqvist, Claes
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen.
    Greger, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Arsenic accumulation and speciation in plants from different habitats2012Inngår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 27, nr 3, s. 615-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding As accumulation in plants is necessary in order to alleviate problems with As in the environment and to improve sustainable As phytotechnologies. To find suitable candidates for phytoremediation purposes and to investigate specific accumulation patterns due to growth habitat and plant groups, As accumulation in 124 plant species collected from different habitats and speciation in 6 of these plant species, was determined. The data show that submerged plants have a higher accumulation than emergent and terrestrial plants. The As concentration in terrestrial and emergent plants were correlated with the [As](soil), while the accumulation factor correlated negatively with [As](soil). Gymnosperms had a high [As](shoot):[As](root) ratio. The inorganic As species, arsenate and arsenite were found in plants from all habitats and methylarsonic acid (MMA) in all but one plant species. Arsenate predominated in submerged plants. The results suggest that the habitat and the [As](soil) have a strong influence on the As accumulation in plants and that submerged plants and/or gymnosperms might be suitable for phytoremediation of As.

  • 50.
    Bergqvist, Claes
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Greger, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Oxygen influences on arsenic behaviour in sediment-water-plant system of Elodea canadensisManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Phytofiltration can be used to remove arsenic (As) from water using the submerged macrophyte Elodea canadensis. To understand the effects of aeration on this system, we investigated the influence of different O2 levels on the As concentration and speciation in sediment, water and E. canadensis,and the efficiency of phytofiltration of As by this plant. The water in pots with As, E. canadensis and/or sediment were aerated with N2, air or left unmodified to create low, high and medium O2 levels, respectively. Analyses of As concentration and species were performed with HPLC-AAS. The results showed that the As accumulation properties by E. canadensis decreased at high O2. Medium O2 had the lowest As release from sediment to water and among the highest plant As accumulation. Arsenate predominated in the sediment-water-plant system, but arsenite increased with decreasing O2. To create conditions favouring the binding of As in sediment and accumulation from water by E. canadensis, the O2 concentration should be medium.

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