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  • 1.
    Alonso Aller, Elisa
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Eveleens Maarse, Floriaan K. J.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gren, Michaela
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Nordlund, Lina Mtwana
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. WIO CARE, Zanzibar, Tanzania.
    Jiddawi, Narriman
    Eklöf, Johan S.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Single and joint effects of regional- and local-scale variables on tropical seagrass fish assemblages2014In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, no 10, p. 2395-2405Article in journal (Refereed)
    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.

  • 2.
    Donadi, Serena
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Hanse-Wissenschaftkolleg - Institute for Advanced Study, Germany.
    Eriksson, Britas Klemens
    Lettmann, Karsten Alexander
    Hodapp, Dorothee
    Wolff, Joerg-Olaf
    Hillebrand, Helmut
    The body-size structure of macrobenthos changes predictably along gradients of hydrodynamic stress and organic enrichment2015In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, no 3, p. 675-685Article in journal (Refereed)
    Abstract [en]

    Body size is related to an extensive number of species traits and ecological processes and has therefore been suggested as an effective metric to assess community changes and ecosystem's state. However, the applicability of body size as an ecological indicator in benthic environments has been hindered by the poor knowledge of the factors influencing the size spectra of organisms. By applying biological trait analysis (BTA) and generalized linear models to a species dataset collected in the German Wadden Sea (53A degrees 41'14'' N, 7A degrees 14'19'' E) between 1999 and 2012, we show that the size structure of the macrobenthic community changes predictably along environmental gradients. Specifically, body size increases with increasing current-induced shear stress and sediment organic matter content. In addition, the presence of oyster-mussel reefs in one of the sampling stations enhanced the survival of species belonging to the smallest size categories in habitats with high hydrodynamic energy. This was probably due to the local sheltering effects, which together with biodeposition also increased organic matter in the sediment, likely favoring large deposit feeders as well. Our results suggest that body size can be a useful trait for estimating effects of anthropogenic stressors, such as organic enrichment or alteration of hydrodynamic regime and could therefore be effectively included in current monitoring programs of intertidal macrobenthic communities.

  • 3.
    Eggertsen, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Chacin, D. H.
    Åkerlund, C.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Swedish University of Agricultural Sciences, Sweden.
    Contrasting distribution and foraging patterns of herbivorous and detritivorous fishes across multiple habitats in a tropical seascape2019In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 166, no 4, article id 51Article in journal (Refereed)
    Abstract [en]

    Understanding drivers behind patterns of functionally important groups of fishes is crucial for successful management and conservation of tropical seascapes. Herbivorous fishes are the most prominent consumers of marine primary production which can have profound effects on reef resilience. We explored environmental variables affecting distribution and foraging patterns of herbivorous and detritivorous fish assemblages (siganids, acanthurids and parrotfish) across distinct shallow-water habitats (coral reefs, macroalgae beds and seagrass meadows) during September-November 2016 at Mafia Island, Tanzania (8 degrees 00S, 39 degrees 41E). We performed underwater visual census to quantify fish assemblages, measured habitat features, deployed macroalgal assays and conducted inventories of grazing scars. Multi-dimensional scaling and mixed-effects linear models were used to evaluate differences in fish assemblages and environmental variables influencing abundance and foraging patterns of fishes. Fish communities of focal functional groups differed among habitats. Abundance of herbivores and detritivores as well as relative browsing and scraping was highest on coral reefs compared to macroalgae and seagrass meadows.Adult fish were more abundant on coral reefs while juveniles were abundant in macroalgal beds. Coral cover and crustose coralline algal cover had a positive effect on the abundance of fish in coral reef areas, while macroalgal cover had a negative effect. Contrastingly, in macroalgae habitats, macroalgal cover had a positive effect on the abundance of parrotfish. These results highlight the importance of considering connectivity between macroalgal beds and coral reefs through ontogenetic shifts in habitat use by primarily microphagous parrotfish and of incorporating a range of habitats within coastal management plans.

  • 4. Eriksson, Britas Klemens
    et al.
    van Sluis, Christiaan
    Sieben, Karin
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Råberg, Sonja
    Stockholm University, Faculty of Science, Department of Botany.
    Omnivory and grazer functional composition moderate cascading trophic effects in experimental Fucus vesiculosus habitats2011In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 158, no 4, p. 747-756Article in journal (Refereed)
    Abstract [en]

    We tested the relative strength of direct versus indirect effects of an aquatic omnivore depending on the functional composition of grazers by manipulating the presence of gastropod and amphipod grazers and omnivorous shrimp in outdoor mesocosms. By selectively preying upon amphipods and reducing their abundance by 70-80%, omnivorous shrimp favoured the dominance of gastropods. While gastropods were the main microalgal grazers, amphipods controlled macroalgal biomass in the experiment. However, strong predation on the amphipod by the shrimp had no significant indirect effects on macroalgal biomass, indicating that when amphipod abundances declined, complementary feeding by the omnivore on macroalgae may have suppressed a trophic cascade. Accordingly, in the absence of amphipods, the shrimp grazed significantly on green algae and thereby suppressed the diversity of the macroalgal community. Our experiment demonstrates direct consumer effects by an omnivore on both the grazer and producer trophic levels in an aquatic food web, regulated by prey availability.

  • 5.
    Friis Møller, Eva
    et al.
    National Environmental Research Institute,.
    Andersen Borg, Christian Marc
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Jonasdottir, Sigrun H.
    National Institute of Aquatic Resources.
    Satapoomin, Suree
    Phuket Marine Biological Center.
    Jaspers, Cornelia
    National Institute of Aquatic Resources.
    Nielsen, Torkel Gissel
    National Institute of Aquatic Resources.
    Production and fate of copepod fecal pellets acrossthe Southern Indian Ocean2011In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 158, no 3, p. 677-688Article in journal (Refereed)
    Abstract [en]

    The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore, the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 mu g C m(-3) day(-1). At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical export of fecal pellets was low (< 0.02 mg m(-2) day(-1)).

  • 6.
    Gullström, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Baden, Susanne
    Lindegarth, Mats
    Spatial patterns and environmental correlates in leaf-associated epifaunal assemblages of temperate seagrass (Zostera marina) meadows2012In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, no 2, p. 413-425Article in journal (Refereed)
    Abstract [en]

    We estimated and tested variability of seagrass leaf-associated epifaunal assemblages at a range of scales. Sampling was performed in 36 seagrass (Zostera marina) meadows within three regions along the Swedish west coast following a hierarchical design (samples separated by 10 s m, km or 100 km). Results showed strongest variability (43-81%) at the intermediate amongst-meadow (km) scale using biomass of functional categories, while considering taxa composition the within-meadow (10 s m) scale contributed most to variability (60%). Using functional categories, we found that embayment exposure and seagrass shoot density were the most important predictor variables explaining part of the variability in biomass of suspension feeders (bivalves and barnacles) and grazers. In contrast, variability in epifaunal taxa composition was predicted mainly by sediment chemistry, substratum coverage and geographical positioning. Our findings suggest that models to develop predictive power and mechanistic understanding should focus on variables and processes varying at small and intermediate scales rather than those varying at larger scales.

  • 7.
    Gullström, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Faculty of Science, Department of Zoology.
    Berkström, Charlotte
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Öhman, Marcus C.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bodin, Maria
    Dahlberg, Mattis
    Stockholm University, Faculty of Science, Department of Zoology.
    Scale-dependent patterns of variability of a grazing parrotfish (Leptoscarus vaigiensis) in a tropical seagrass-dominated seascape2011In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 158, no 7, p. 1483-1495Article in journal (Refereed)
    Abstract [en]

    Although herbivorous fish form critical linkages between primary producers and higher trophic levels, the major factors regulating their spatial structure in seagrass systems remain poorly understood. The present study examined the parrotfish Leptoscarus vaigiensis in seagrass meadows of a tropical embayment in the western Indian Ocean. Stomach content analysis and direct field observations showed that L. vaigiensis is an efficient grazer, feeding almost exclusively on seagrass leaves. Seagrass shoot density was highly correlated to all density variables (total, juvenile and subadult) and juvenile biomass of L. vaigiensis, while subadult biomass was predicted by distance to neighbouring coral habitat. Moreover, density and biomass of predatory fish (piscivores) were predicted by seagrass canopy height and the distribution patterns of predators followed those of L. vaigiensis. Hence, factors at local (seagrass structural complexity and feeding mode) and landscape scale levels (seascape context and distribution of piscivores) likely mutually structure herbivorous fish communities. The findings underscore the importance of incorporating multiple scale-dependent factors when managing coastal seagrass ecosystems and their associated key species.

  • 8.
    Hansen, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Sagerman, Josefin
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sofia, Wikström
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Effects of plant morphology on small-scale distribution of invertebrates2010In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 157, no 10, p. 2143-2155Article in journal (Refereed)
    Abstract [en]

    Habitat structure influences organism communities by mediating interactions between individuals and species, affecting abundance and species richness. We examined whether variations in the morphology of soft-bottom plants affect their function as habitat and whether complex structured plants support higher macroinvertebrate abundance and species richness. Three Baltic Sea plant species were studied, together with artificial plants resembling each species. In a field collection, we found higher invertebrate abundance on the morphologically more complex plants Myriophyllum spicatum and Chara baltica than on the structurally simpler plant Potamogeton perfoliatus. In a colonization experiment, we found the highest invertebrate abundance on artificial M. spicatum but found no difference between natural plants. Invertebrate taxon richness displayed no consistent relationship with plant structural complexity. The results imply that plant morphology influences small-scale invertebrate distribution, partly supporting the hypothesis that structurally complex plants harbour higher invertebrate abundance.

  • 9.
    Hellström, Micaela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kavanagh, Kathryn D.
    Benzie, John A. H.
    Multiple spawning events and sexual reproduction in the octocoral Sarcophyton elegans (Cnidaria: Alcyonacea) on Lizard Island, Great Barrier Reef2010In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 157, no 2, p. 383-392Article in journal (Refereed)
    Abstract [en]

    Sarcophyton elegans is a common symbiotic (zooxanthellate) octocoral species in the shallow waters of the Great Barrier Reef (GBR). Study of a population at Lizard Island (14°40′S, 145°28′E) on the GBR from October 1991 to January 1994 revealed that, as is typical of tropical alcyonarian corals, S. elegans is a gonochoric broadcast spawner with a 1:1 sex ratio. Sexual reproduction was closely correlated with colony size, with first reproduction at 13-cm basal stalk circumference for females and 12 cm for males. Oogenesis took 19–24 months, with a new cycle commencing every year, and spermatogenesis took 10–12 months. The majority of gametes were released during the annual austral mass coral spawning event after the full moon in November, but gametes were also released after the full moon in each month between August and February. All autozooid polyps participated in reproduction, but those at the outer edge of a colony released their gametes first. During subsequent months, the polyps closer to the center of the colony released their gametes. This is a novel strategy of gamete release, reported here for the first time, which accommodates the demands of feeding and reproduction in a different way than other corals where individual polyps have separate feeding or reproductive roles. Colonies upstream in the prevailing current spawned up to 1 month earlier than those downstream and ceased 1 month earlier. The mechanism controlling this spatial differentiation in spawning time, repeatedly observed over three seasons, is unknown. Sarcophyton elegans appears to have a dual strategy of providing protection for its gametes by releasing most of them concurrently with the single, annual mass spawning of a large number of cnidarians, while also hedging its bets by individual colonies spawning a fraction of their gametes over an extended period of 6 months.

  • 10.
    Holmborn, Towe
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Erratum to: Relationships between RNA content and egg production rate in Acartia bifilosa (Copepoda, Calanoida) of different spatial and temporal origin2008In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 153, no 5, p. 1007-1008Article in journal (Refereed)
  • 11. Jungerstam, Jennifer
    et al.
    Erlandsson, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    McQuaid, Christopher D.
    Porri, Francesca
    Westerbom, Mats
    Kraufvelin, Patrik
    Is habitat amount important for biodiversity in rocky shore systems?: A study of South African mussel assemblages2014In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, no 7, p. 1507-1519Article in journal (Refereed)
    Abstract [en]

    Habitat-forming species on rocky shores are often subject to high levels of exploitation, but the effects of subsequent habitat loss and fragmentation on associated species and the ecosystem as a whole are poorly understood. In this study, the effects of habitat amount on the fauna associated with mussel beds were investigated, testing for the existence of threshold effects at small landscape scales. Specifically, the relationships between mussel or algal habitat amount and: associated biodiversity, associated macrofaunal abundance and density of mussel recruits were studied at three sites (Kidd's Beach, Kayser's Beach and Kini Bay) on the southern and south-eastern coasts of South Africa. Samples, including mussel-associated macrofauna, of 10 x 10 cm were taken from areas with 100 % mussel cover (Perna perna or a combination of P. perna and Mytilus galloprovincialis) at each site. The amount of habitat provided by mussels and algae surrounding the sampled areas was thereafter determined at the 4.0 m(2) scale. A number of significant positive relationships were found between the amount of surrounding mussel habitat and the abundances of several taxa (Anthozoa, Malacostraca and Nemertea). Likewise, there were positive relationships between the amount of surrounding algal habitat and total animal abundance as well as abundance of mussel recruits at one site, Kini Bay. In contrast, abundance of mussel recruits showed a significant negative relationship with the amount of mussel habitat at Kayser's Beach. Significant negative relationships were also detected between the amount of mussel habitat and species richness and total abundance at Kidd's Beach, and between amount of mussel habitat and the abundance of many taxa (Bivalvia, Gastropoda, Maxillopoda, Ophiuroidea, Polychaeta and Pycnogonida) at all three sites. No threshold effects were found, nor were significant relationships consistent across the investigated sites. The results indicate that the surrounding landscape is important in shaping the structure of communities associated with these mussel beds, with significant effects of the amount of surrounding habitat per se. The strength and the direction of habitat effects vary, however, between shores and probably with the scale of observation as well as with the studied dependent variables (e.g. diversity, abundance, mussel recruitment, species identity), indicating the complexity of the processes structuring macrofaunal communities on these shores.

  • 12.
    Karlsson, Konrad
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Puiac, Simona
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Life-history responses to changing temperature and salinity of the Baltic Sea copepod Eurytemora affinis2018In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 165, no 2, article id 30Article in journal (Refereed)
    Abstract [en]

    To understand the effects of predicted warming and changing salinity of marine ecosystems, it is important to have a good knowledge of species vulnerability and their capacity to adapt to environmental changes. In spring and autumn of 2014, we conducted common garden experiments to investigate how different populations of the copepod Eurytemora affinis from the Baltic Sea respond to varying temperatures and salinity conditions. Copepods were collected in the Stockholm archipelago, Bothnian Bay, and Gulf of Riga (latitude, longitude: 58 degrees 48.19', 17 degrees 37.52'; 65 degrees 10.14', 23 degrees 14.41'; 58 degrees 21.67', 24 degrees 30.83'). Using individuals with known family structure, we investigated within population variation of the reaction norm (genotype and salinity interaction) as a means to measure adaptive capacity. Our main finding was that low salinity has a detrimental effect on development time, the additive effects of high temperature and low salinity have a negative effect on survival, and their interaction has a negative effect on hatching success. We observed no variation in survival and development within populations, and all genotypes had similar reaction norms with higher survival and faster development in higher salinities. This suggests that there is no single genotype that performs better in low salinity or high salinity; instead, the best genotype in any given salinity is best in all salinities. Genotypes with fast development time also had higher survival compared to slow developing genotypes at all salinities. Our results suggest that E. affinis can tolerate close to freshwater conditions also in high temperatures, but with a significant reduction in fitness.

  • 13.
    Norström, Albert
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lokrantz, Jerker
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Nyström, Magnus
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Yap, HT
    Influence of dead coral substrate morphology on patterns of juvenile coral distribution2007In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 150, no 6, p. 1145-1152Article in journal (Refereed)
    Abstract [en]

    This study examines the abundances of three morphological categories of juvenile corals (massive, branching and encrusting) on two different types of natural substratum, dead massive and dead branching corals. The overall results show that the morphological characteristics of dead coral substratum have a significant influence on the coral recruitment patterns with respect to the morphology of the recruits: juvenile corals of massive and branching types were more abundant on substrates of corresponding morphology. The results obtained from this study suggest that dead coral might attract coral larvae that are morphologically similar. On the other hand, it may be the result of post-settlement mortality. Whatever the mechanism shaping the patterns is, it seems that the physical morphology of the dead coral substrate has a significant influence on the coral recruit assemblage. Hence, we suggest that substrate morphology can be an important qualitative factor for coral settlement and a possible determinant of community structure.

  • 14.
    Olafsson, Emil
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Aarnio, Katri
    Bonsdorff, Erik
    Larissa Arroyo, Nina
    Fauna of the green alga Cladophora glomerata in the Baltic Sea: density, diversity, and algal decomposition stage2013In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 160, no 9, p. 2353-2362Article in journal (Refereed)
    Abstract [en]

    The green alga Cladophora glomerata (L.) is a common macrophyte in the northern Baltic Sea, where it forms drifting mats during summer. We studied the effect of its stage of decomposition on the density, diversity, and resource usage of associated meio- and macrofauna. We hypothesised that mobile species would show small variation in food preferences among decomposition stages, while high variation was expected in stationary species, as reflected in their stable isotope signatures. The assemblage structure of the fauna differed between the 3 studied algal degradation stages, Green (attached, healthy), Degraded (attached, but starting to decay), and Drift (detached, decaying). C/N ratios were highest in green algae and decreased in decaying algal stages. Variation in stable isotope ratios of stationary and mobile species supported our resource use hypothesis. The decomposition stage of C. glomerata significantly affected the carbon and nitrogen stable isotope ratios of both the alga and its main grazer species. Higher invertebrate diversity in the more decaying stages was probably facilitated by decomposer microbes adding resource types and by the proximity of the detached algal mats to the sediment.

  • 15. Porri, Francesca
    et al.
    McQuaid, Christopher D.
    Erlandsson, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology. Swedish University of Agricultural Sciences, Sweden.
    The role of recruitment and behaviour in the formation of mussel-dominated assemblages: an ontogenetic and taxonomic perspective2016In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 163, no 7, article id 157Article in journal (Refereed)
    Abstract [en]

    Behaviour influences individual fitness with effects that can propagate from the individual to the group. Here, we tested for higher-level effects of individual behaviour in the structuring of intertidal populations of two competing ecosystem engineering species. We used the partial habitat segregation exhibited by co-occurring indigenous (Perna perna) and invasive (Mytilus galloprovincialis) mussels in South Africa to test for possible attraction of different size classes of recruits to conspecific adults, using a combination of field and laboratory studies. Each of the two species dominates a particular height on the shore with overlap in the mid-mussel zone, but measurements of settlement and recruitment in the field partially refuted previous findings, generally showing no within-shore pattern of zonation of settlers and recruits. At smaller scales, recruits of both species were found more frequently on adults of Mytilus in natural beds where adults coexist in mixed-species populations. Finally, the results of laboratory choice experiments showed that recruits of all sizes responded to adult cues by movement, but that the smallest recruits showed only minimal movement and never reached adults; only large recruits of Perna responded positively to conspecific Perna adults. This study emphasises how observations made at different scales, from shore (among sites) to mussel bed (within shores), to the individual (field and laboratory), can produce different, or even contrasting, information, highlighting how behavioural traits, like attraction to conspecifics, can differ within the same group of organisms (congeneric species) and change ontogenetically within a species. Incorporating fine-scale responses makes predictions of population dynamics more complex, but identifying the relative strengths of mechanisms that lead to patterns of distribution is necessary for understanding higher-level interactions within a system.

  • 16.
    Rasmusson, Lina M.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lauritano, Chiara
    Procaccini, Gabriele
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Buapet, Pimchanok
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Prince of Songkla University, Thailand.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Respiratory oxygen consumption in the seagrass Zostera marina varies on a diel basis and is partly affected by light2017In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 164, no 6, article id 140Article in journal (Refereed)
    Abstract [en]

    The seagrass Zostera marina is an important marine ecosystem engineer, greatly influencing oxygen and carbon fluctuations in temperate coastal areas. Although photosynthetically driven gas fluxes are well studied, the impact of the plant's mitochondrial respiration on overall -CO2 and -O-2 fluxes in marine vegetated areas is not yet understood. Likewise, the gene expression in relation to the respiratory pathway has not been well analyzed in seagrasses. This study uses a combined approach, studying respiratory oxygen consumption rates in darkness simultaneously with changes in gene expression, with the aim of examining how respiratory oxygen consumption fluctuates on a diel basis. Measurements were first made in a field study where samples were taken directly from the ocean to the laboratory for estimations of respiratory rates. This was followed by a laboratory study where measurements of respiration and expression of genes known to be involved in mitochondrial respiration were conducted for 5 days under light conditions mimicking natural summer light (i.e.,15 h of light and 9 h of darkness), followed by 3 days of constant darkness to detect the presence of a potential circadian clock. In the field study, there was a clear diel variation in respiratory oxygen consumption with the highest rates in the late evening and at night (0.766 and 0.869 mu mol -O-2 m(-2) s(-1), respectively). These repetitive diel patterns were not seen in the laboratory, where water conditions (temperature, pH, and oxygen) showed minor fluctuations and only light varied. The gene expression analysis did not give clear evidence on drivers behind the respiratory fluxes; however, expression levels of the selected genes generally increased when the seagrass was kept in constant darkness. While light may influence mitochondrial respiratory fluxes, it appears that other environmental factors (e.g., temperature, pH, or oxygen) could be of significance too. As seagrasses substantially alter the proportions of both oxygen and inorganic carbon in the water column and respiration is a great driver of these alterations, we propose that acknowledging the presence of respiratory fluctuations in nature should be considered when estimating coastal carbon budgets. As dark respiration in field at midnight was approximately doubled from that of midday, great over-, or underestimations of the respiratory carbon dioxide release from seagrasses could be made if values are just obtained at one specific time point and considered constant.

  • 17.
    Sagerman, Josefin
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Enge, Swantje
    Pavia, Henrik
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Low feeding preference of native herbivores for the successful non-native seaweed Heterosiphonia japonica2015In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, no 12, p. 2471-2479Article in journal (Refereed)
    Abstract [en]

    Non-native seaweeds constitute a conspicuous component of many benthic coastal communities. Seaweed invaders are known to significantly affect invaded communities, but relatively little is known about the mechanisms underlying their success. In this study, we explored the feeding preferences of three generalist herbivores for the successful non-native red alga Heterosiphonia japonica and native seaweed competitors. The experiments were conducted on the Swedish Skagerrak coast (58A degrees 52'N, 11A degrees 08'E) from July to August. Additionally, chemical and physical traits of the seaweeds were assessed to mechanistically explain herbivore preferences. The results showed that H. japonica was of low preference to native herbivores and that this was most likely explained by chemical properties of the invader. We were, however, not able to determine whether the low preference was caused by deterrent metabolites or low nutritional quality. We conclude that herbivore avoidance may be important for the survival and success of H. japonica in the introduced range and that efficient means of escaping herbivory may be a common feature of invaders in seaweed communities.

  • 18. Sainmont, Julie
    et al.
    Gislason, Astthor
    Heuschele, Jan
    Webster, Clare N.
    Sylvander, Peter
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wang, Miao
    Varpe, Oystein
    Inter- and intra-specific diurnal habitat selection of zooplankton during the spring bloom observed by Video Plankton Recorder2014In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, no 8, p. 1931-1941Article in journal (Refereed)
    Abstract [en]

    Diel vertical migration (DVM) is a common behavior adopted by zooplankton species. DVM is a prominent adaptation for avoiding visual predation during daylight hours and still being able to feed on surface phytoplankton blooms during night. Here, we report on a DVM study using a Video Plankton Recorder (VPR), a tool that allows mapping of vertical zooplankton distributions with a far greater spatial resolution than conventional zooplankton nets. The study took place over a full day-night cycle in Disko Bay, Greenland, during the peak of the phytoplankton spring bloom. The sampling revealed a large abundance of copepods performing DVM (up during night and down during day). Migration behavior was expressed differently among the abundant groups with either a strong DVM (euphausiids), an absence of DVM (i.e., permanently deep; ostracods) or a marked DVM, driven by strong surface avoidance during the day and more variable depth preferences at night (Calanus spp.). The precise individual depth position provided by the VPR allowed us to conclude that the escape from surface waters during daytime reduces feeding opportunities but also lowers the risk of predation (by reducing the light exposure) and thereby is likely to influence both state (hunger, weight and stage) and survival. The results suggest that the copepods select day and night time habitats with similar light levels (similar to 10(-9) mu mol photon s(-1) m(-2)). Furthermore, Calanus spp. displayed state-dependent behavior, with DVM most apparent for smaller individuals, and a deeper residence depth for the larger individuals.

  • 19. Sommer, Ulrich
    et al.
    Adrian, Rita
    Bauer, Barbara
    Winder, Monika
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    The response of temperate aquatic ecosystems to global warming: novel insights from a multidisciplinary project2012In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, no 11, p. 2367-2377Article, review/survey (Refereed)
    Abstract [en]

    This article serves as an introduction to this special issue of Marine Biology, but also as a review of the key findings of the AQUASHIFT research program which is the source of the articles published in this issue. AQUASHIFT is an interdisciplinary research program targeted to analyze the response of temperate zone aquatic ecosystems (both marine and freshwater) to global warming. The main conclusions of AQUASHIFT relate to (a) shifts in geographic distribution, (b) shifts in seasonality, (c) temporal mismatch in food chains, (d) biomass responses to warming, (e) responses of body size, (f) harmful bloom intensity, (f), changes of biodiversity, and (g) the dependence of shifts to temperature changes during critical seasonal windows.

  • 20.
    Tano, Stina A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Halling, Christina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Lind, Emma
    Buriyo, Amelia
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Extensive spread of farmed seaweeds causes a shift from native to non-native haplotypes in natural seaweed beds2015In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, no 10, p. 1983-1992Article in journal (Refereed)
    Abstract [en]

    Seaweed farming has been the cause of introductions of non-indigenous seaweed species and genotypes throughout the world. In Zanzibar, Tanzania, foreign genotypes of Eucheuma denticulatum were introduced for farming purposes in 1989, and in recent years a spread of non-indigenous haplotypes has been reported. The current study aimed to investigate the presence and extent of introduced and native haplotypes of E. denticulatum as well as their relative frequencies, to obtain the severity of the spread of cultivated seaweed and the current state of the native populations. The results show that all investigated sites are dominated by the introduced South-east Asian haplotypes, even where seaweed farming has never occurred. As the frequencies of East African haplotypes are remarkably low, this shows a shift from native to introduced E. denticulatum. This shift may, at least in part, be caused by earlier overharvest of natural seaweed populations, and indicates a cryptic invasion of the introduced haplotypes at the potential cost of the recovery of the native haplotype populations.

  • 21. Tverin, Malin
    et al.
    Westberg, Melissa
    Kokkonen, Iiris
    Tang, Patrik
    Lehmann, Philipp
    Stockholm University, Faculty of Science, Department of Zoology.
    Lundström, Karl
    Käkelä, Reijo
    Factors affecting the degree of vertical stratification of fatty acids in grey seal blubber2019In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 166, no 8, article id 105Article in journal (Refereed)
    Abstract [en]

    The biochemistry of marine mammal blubber differs vertically from skin to muscle, which forms a challenge for using fatty acids (FAs) from differently sampled blubber as a proxy for dietary studies required for ecosystem-based management of coastal resources. In the blubber of some phocid seal individuals, the vertical stratification of several FAs is pronounced whereas in others the FAs distribute almost evenly through the blubber column. Using gas chromatography, we analysed the blubber vertical FA profiles of 30 adult male grey seals from the Baltic Sea, and examined which factors induced the largest vertical change of FA composition detected at the depth of 15-18mm (outer and middle blubber boundaries). It was revealed that the degree of this compositional shift did not depend on the blubber thickness. Seal age only affected the vertical distribution of the FAs 16:0 and 16:1n-7. However, the outer blubber ratio of 9-desaturated monounsaturated FAs (MUFAs) to their saturated FA (SFA) precursors was not increased by grey seal age, contrasting earlier findings for ringed seals. A major determinant of the degree of FA stratification between the outer and middle blubber was the mismatch between the individually varying FA composition of the innermost blubber, regarded to reflect the dietary FA supply the most, and the uniform FA composition of endogenously regulated MUFA-rich outer blubber. Thus, discarding a fixed-depth layer of the grey seal outermost blubber, which we here show to span 0-18mm from skin and which to a lesser extent reflects the diet of the individual, may in the case of small pinnipeds improve the sensitivity of the FA analysis in assessing spatial, temporal and individual dietary differences. When studying the outer blubber samples using only the diet-derived PUFA variables (SFAs and MUFAs omitted), the sensitivity of the analysis was better than when using this sample type with all main FA variables included.

  • 22.
    Uku, Jacqueline
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Beer, Sven
    Björk, Mats
    Buffer sensitivity of photosynthetic carbon utilization in eight tropical seagrasses2005In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 147, no 5, p. 1085-1090Article in journal (Refereed)
    Abstract [en]

    Some of the mechanisms involved in inorganic carbon (Ci) acquisition by tropical seagrasses from the western Indian Ocean were described by Björk et al. (Mar Biol 129:363–366, 1997). However, since then, it has been found that an additional, buffer-sensitive, system of Ci utilisation may operate in some temperate seagrasses (Hellblom et al. in Aquat Bot 69:55–62, 2001, Hellblom and Axelsson in Photos Res 77:173–191, 2003); this buffer sensitivity indicates a mechanism in which electrogenic H+ extrusion may form acidic diffusion boundary layers, in which either HCO3–H+ is co-transported into the cells, or where HCO3 is converted to CO2 (as catalysed by carbonic anhydrase) prior to uptake of the latter Ci form. Because a buffer was used in the 1997 study, we found it important to reinvestigate those same eight species, taking into account the direct effect of buffers on this potential mode of Ci acquisition in these plants. In doing so, it was found that all seagrass species investigated except Cymodocea serrulata were sensitive to 50 mM TRIS buffer of the same pH as the natural seawater in which they grew (pH 8.0). Especially sensitive were Halophila ovalis, Halodule wrightii and Cymodocea rotundata, which grow high up in the intertidal zone (only ca. 50–65% of the net photosynthetic activity remained after the buffer additions), followed by the submerged Enhalus acoroides and Syringodium isoetifolium (ca. 75% activity remaining), while Thalassia hemprichii and Thalassodendron ciliatum, which grow in-between the two zones, were less sensitive to buffer additions (ca. 80–85% activity remaining). In addition to buffer sensitivity, all species were also sensitive to acetazolamide (AZ, an inhibitor of extracellular carbonic anhydrase activity) such that ca. 45–80% (but 90% for H. ovalis) of the net photosynthetic activity remained after adding this inhibitor. Raising the pH to 8.8 (in the presence of AZ) drastically reduced net photosynthetic rates (0–14% remaining in all species); it is assumed that this reduction in rates was due to the decreased CO2 concentration at the higher pH. These results indicate that part of the 1997 results for the same species were due to a buffer effect on net photosynthesis. Based on the present results, it is concluded that (1) photosynthetic Ci acquisition in six of the eight investigated species is based on carbonic anhydrase catalysed HCO3 to CO2 conversions within an acidified diffusion boundary layer, (2) C. serrulata appears to support its photosynthesis by extracellular carbonic anhydrase catalysed CO2 formation from HCO3 without the need for acidic zones, (3) H. ovalis features a system in which H+ extrusion may be followed by HCO3–H+ co-transport into the cells, and (4) direct, non-H+-mediated, uptake of HCO3 is improbable for any of the species.

  • 23. Visram, Shakil
    et al.
    Yang, Ming-Che
    Pillay, Ruby Moothien
    Said, Sadri
    Henriksson, Oskar
    Södertörns högskola.
    Grahn, Mats
    Chen, Chaolun Allen
    Genetic connectivity and historical demography of the blue barred parrotfish (Scarus ghobban) in the western Indian Ocean2010In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 157, no 7, p. 1475-1487Article in journal (Refereed)
    Abstract [en]

    Studies on genetic connectivity are essential for the design of management strategies for coral reef fisheries. In this study we used a mitochondrial DNA marker to investigate population structure of the reef-associated parrotfish, Scarus ghobban, from four countries, Kenya, Mauritius, Seychelles and Tanzania, in the western Indian Ocean. We obtained nucleotide sequences of the mitochondrial control region for 117 individuals. Measures of haplotype diversity were relatively high. Pairwise population differentiation (F (ST)) was low, but not always non-significant. Analysis of molecular variance (AMOVA) showed genetic differentiation between groups, when the data was partitioned into two groups consisting of samples from Mauritius and Tanzania in one group, and samples from Kenya and Seychelles in another group. Direction of gene flow was estimated using a Bayesian approach. Migration was sometimes asymmetric or directional, coinciding with the flow of major oceanic and coastal currents in the region. Mismatch distributions, based on the observed number of differences among haplotype pairs, produced a unimodal distribution, indicative of recent demographic expansion. Phylogenetic analyses revealed three clades without any geographic structure, suggesting recent migration between historically isolated lineages. We reconstructed the historical demography of S. ghobban and examined it in the context of Pleistocene climate stages and changes in relative sea level. Overall, these results showed that populations of S. ghobban are genetically diverse and have relatively high gene flow, with some genetic structuring in the western Indian Ocean.

  • 24. Webster, Clare N.
    et al.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Didrikas, Tomas
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Peltonen, Heikki
    Brierley, Andrew S.
    Lehtiniemi, Maiju
    Stuck between a rock and a hard place: zooplankton vertical distribution and hypoxia in the Gulf of Finland, Baltic Sea2015In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, no 7, p. 1429-1440Article in journal (Refereed)
    Abstract [en]

    Zooplankton often migrate vertically to deeper dark water during the day to avoid visual predators such as fish, a process which can strengthen benthic-pelagic coupling. In the Gulf of Finland, Baltic Sea, a pronounced hypoxic layer develops when there is an inflow of anoxic bottom water from the Central Baltic Sea, which could be a barrier for vertical migrants. Here, we report an acoustic study of the distributions of crustacean zooplankton (mysid shrimp and the copepod Limnocalanus macrurus), gelatinous zooplankton (Aurelia aurita) and fish. Zooplankton trawl nets were used to ground-truth acoustic data. Vertical profiles of oxygen concentration were taken, and the physiological impact of hypoxia on mysids was investigated using biochemical assays. We hypothesised that the vertical distribution of zooplankton and fish would be significantly affected by vertical heterogeneity of oxygen concentrations because anoxia and hypoxia are known to affect physiology and swimming behaviour. In addition, we hypothesised that mysids present in areas with hypoxia would exhibit a preparatory antioxidant response, protecting them from oxidative damage during migrations. The acoustic data showed peaks of crustacean zooplankton biomass in hypoxic (< 2 mL L-1) and low oxygen (2-4 mL L-1) concentrations (depth > 75 m), whereas fish shoals and A. aurita medusae were found in normoxic (5-6 mL L-1) upper water layers (< 40 m), with individual fish in deeper water excepting that rule. Mysid shrimp from areas with hypoxia had significantly enhanced antioxidant potential compared with conspecifics from areas with no hypoxia and had no significant indications of oxidative damage. We conclude that mysids can protect themselves from oxidative damage, enabling them to inhabit hypoxic water. Our data suggest that hypoxic and low oxygen zones (up to 4 mL L-1) may provide some zooplankton species with a refuge from visual predators such as fish.

  • 25.
    Wikström, Sofia A.
    et al.
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Carstensen, Jacob
    Blomqvist, Mats
    Krause-Jensen, Dorte
    Cover of coastal vegetation as an indicator of eutrophication along environmental gradients2016In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 163, no 12, article id 257Article in journal (Refereed)
    Abstract [en]

    Coastal vegetation communities are important for primary production, biodiversity, coastal protection, carbon and nutrient cycling which, in combination with their sensitivity to eutrophication, render them potential indicators of environmental status for environmental policies like the EU Water and Marine Strategy Framework Directives. We evaluated one potential indicator for coastal vegetation, the cumulative cover at depths where the vegetation is light limited, by investigating its response to eutrophication along gradients in natural conditions. We used a large data set covering the Swedish coastline, spanning broad gradients in nutrient level, water clarity, sea-bed substrate, physical exposure and climate in addition to a salinity gradient from 0.5 to 30.5. Macroalgal cover increased significantly along gradients of declining nutrient concentration and increasing water clarity when we had accounted for diver effects, spatio-temporal sampling variability, salinity gradients, wave exposure and latitude. The developed empirical model explained 79% of the variation in algal cover across 130 areas. Based on this, we identified macroalgal cover as a promising indicator across the Baltic Sea, Kattegat and Skagerrak. A parallel analysis of soft-substrate macrophytes similarly identified significant increases in cover with decreasing concentrations of total nitrogen and increasing salinity, but the resulting empirical model explained only 52% of the variation in cover, probably due to the spatially more variable nature of soft-substrate vegetation. The identified general responses of vegetation cover to gradients of eutrophication across wide ranges in environmental settings may be useful for monitoring and management of marine vegetation in areas with strong environmental gradients.

  • 26.
    Winder, Monika
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Berger, Stella A.
    Lewandowska, Aleksandra
    Aberle, Nicole
    Lengfellner, Kathrin
    Sommer, Ulrich
    Diehl, Sebastian
    Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions2012In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, no 11, p. 2491-2501Article in journal (Refereed)
    Abstract [en]

    Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20-200 mu m)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.

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