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  • 201.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Höglander, Helena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Andersen, Christian Marc
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Stable isotopes show food web changes after invasion by the predatory cladoceran Cercopagis pengoi in a Baltic Sea bay2005In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 143, no 2, p. 251-259Article in journal (Refereed)
    Abstract [en]

    Cercopagis pengoi, a recent invader to the Baltic Sea and the Laurentian Great Lakes, is a potential competitor with fish for zooplankton prey. We used stable C and N isotope ratios to elucidate trophic relationships between C. pengoi, zooplankton (microzooplankton, 90–200 m, mostly copepod nauplii and rotifers; mesozooplankton, >200 m, mostly copepods), and zooplanktivorous fish (herring, size range 5–15 cm and sprat, 9–11 cm) in a coastal area of the northern Baltic Sea. The isotope ratios in C. pengoi and fish were much higher than those of zooplankton, showing general trends of enrichment with trophic level. Young-of-the-year (YOY) herring had a significantly higher 15N/14N ratio than C. pengoi, suggesting of a trophic linkage between the two species. To evaluate the possible relative importance of different food sources for C. pengoi and YOY herring, two-source isotope-mixing models for N were used, with micro- and mesozooplankton as prey for C. pengoi and mesozooplankton and C. pengoi as prey for YOY herring. These models indicate that mesozooplankton was the major food source of both species. However, microzooplankton may be important prey for young stages of C. pengoi. Comparative analyses of the herring trophic position before and after the invasion by C. pengoi showed a trophic level shift from 2.6 to 3.4, indicating substantial alterations in the food web structure. Our findings contribute to a growing body of evidence, showing that C. pengoi can modify food webs and trophic interactions in invaded ecosystems.

  • 202.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kosinkova, Lisa
    Albertsson, Jan
    Umeå universitet.
    Johansen, Marie
    SMHI.
    Djurplankton i våra hav2009In: Havet 2009, p. 35-38Article in journal (Other (popular science, discussion, etc.))
  • 203.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Marin ekologi.
    Lehtiniemi, M
    A combined approach to understand trophic interactions between Cercopagis pengoi (Cladocera: Onychopoda) and mysids in the Gulf of Finland2007In: Limnology and Oceanography, Vol. 52, no 2, p. 822-835Article in journal (Refereed)
  • 204.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lehtiniemi, Maiju
    Finnish Inst Marine Res.
    Viitasalo-Frosen, Satu
    Finnish Inst Marine Res.
    Haddock, Steven H. D.
    Monterey Bay Aquarium Res Inst.
    Molecular evidence for the occurrence of Mertensia ovum in the northern Baltic Sea and implications for the status of Mnemiopsis leidyi invasion.2009In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 54, no 6, p. 2025-2033Article in journal (Refereed)
    Abstract [en]

    Nucleotide sequence analysis of 18S ribosomal RNA gene ( rRNA), internal transcribed spacer, and 5.8S rRNA was used for taxonomic identification of ctenophores collected in the northern Baltic Sea, where invasive Mnemiopsis leidyi and native Pleurobrachia pileus have been reported to occur. Contrary to previous reports, sequence analysis of 53 randomly selected specimens from seven stations revealed that none of them were M. leidyi or P. pileus. The 18S rRNA and 5.8S rRNA sequences were 100% identical to those of Mertensia ovum, a ctenophore with a broad Arctic and circumboreal distribution, which has never been reported to occur in the Baltic Sea. Polymerase chain reaction screening with primers designed to amplify all three species, and using ctenophores collected by vertically stratified sampling, confirmed that all ctenophores collected in this survey were M. ovum. The ctenophore abundance was high, up to 4500 individuals m(-2), positively correlating with salinity. Our findings emphasize the utility of applying molecular tools to biological surveys and the importance of rigorous species identification. They also indicate that M. leidyi, which is a threat to the southern Baltic ecosystem, does not occur in the northern part of the sea, and call for a pan-Baltic survey to establish current distributions of ctenophores, both native and invasive.

  • 205.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Löf, Marie
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Halldorsson, Halldor Palmar
    Tjärnlund, Ulla
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lindström, Magnus
    Elfwing, Tina
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sundelin, Brita
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Single and combined effects of hypoxia and contaminated sediments on the amphipod Monoporeia affinis in laboratory toxicity bioassays based on multiple biomarkers2010In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 99, no 2, p. 263-274Article in journal (Refereed)
    Abstract [en]

    In estuaries, hypoxic conditions and pollution are among the major factors responsible for the declines in habitat quality, yet little is known about their combined effects on estuarine organisms. In this study, to investigate single and combined effects of hypoxia and contaminated sediment, the Baltic amphipod Monoporeia affinis was exposed for 5-9 days to four different combinations of oxygen conditions (moderate hypoxia vs. normoxia) and contamination (polluted vs. unpolluted sediments) at environmentally realistic levels. To detect oxidative stress, a suite of biomarkers was used - antioxidant enzymes [superoxide dismutases (SOD), catalase (CAT), and glutathione S-transferases (GST)], acetylcholinesterase (AChE), lipid peroxidation status (TBARS concentration), protein carbonyl content (PCC), and DNA strand breakage (DNA-SB). To assay effects at the organism level, we used RNA:DNA ratio as a proxy for growth and metabolic rate and mortality. There were significant increases in CAT and SOD activities and TBARS levels in response to both moderate hypoxia and contaminated sediment, while GST increased and AChE decreased in response to the contamination only. Significant positive correlations were observed among the antioxidant enzymes and between the enzyme activities and TBARS concentration, suggesting a complex response to the oxidative stress. No significant changes in PCC were recorded in any of the treatments. Furthermore, the negative effect of hypoxia on DNA integrity was significant; with frequency of DNA-SB increasing in animals exposed to hypoxia in contaminated sediment. Despite clear effect at the cellular and biochemical levels, no responses at the organism level were observed. Multivariate analyses of the dataset have allowed us to link exposure factors to individual biomarker responses. Of the potential biomarkers assessed in this study, CAT activity was found to be associated with hypoxia, while SOD, GST and AChE activities appear to predict best the effects of exposure to sediments containing several contaminants (e.g. heavy metals, PCBs and PAHs), and TBARS concentration is particularly indicative of combined effects of hypoxia and contamination. In addition to providing new knowledge on the combined effects of multiple stressors on estuarine organisms, the findings of the present study are also important to understand data from biomonitoring studies in the Baltic Sea and in other regions where multiple stress factors co-occur.

  • 206.
    Gorokhova, Elena
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Department of Systems Ecology.
    Mattsson, Lisa
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sundström, Annica M.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    A comparison of TO-PRO-1 iodide and 5-CFDA-AM staining methods for assessing viability of planktonic algae with epifluorescence microscopy2012In: Journal of Microbiological Methods, ISSN 0167-7012, E-ISSN 1872-8359, Vol. 89, no 3, p. 216-221Article in journal (Refereed)
    Abstract [en]

    Two fluorescent dyes, TO-PRO-1 iodide and 5-CFDA-AM, were evaluated for LIVE/DEAD assessment of unicellular marine algae Brachiomonas submarina and Tetraselmis suecica. Epifluorescence microscopy was used to estimate cell viability in predetermined mixtures of viable and non-viable algal cells and validated using microplate growth assay as reference measurements. On average, 5-CFDA-AM underestimated live cell abundance by similar to 25% compared with viability estimated by the growth assay, whereas TO-PRO-1 iodide provided accurate viability estimates. Furthermore, viability estimates based on staining with TO-PRO-1 iodide were not affected by a storage period of up to one month in -80 degrees C, making the assay a good candidate for routine assessment of phytoplankton populations in field and laboratory studies.

  • 207. Gorska, N
    et al.
    Cieslik, L
    Didrikas, Tomas
    Stockholm University, Faculty of Science, Department of Systems Ecology. Marin ekologi.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    On acoustic backscattering by Baltic zooplankton2007In: Hydroacoustics, Vol. 10, p. 55-68Article in journal (Refereed)
  • 208.
    Graham, M.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Ernstson, Henrik
    Stockholm University, Stockholm Resilience Centre.
    Comanagement at the Fringes: Examining Stakeholder Perspectives at Macassar Dunes, Cape Town, South Africa-at the Intersection of High Biodiversity, Urban Poverty, and Inequality2012In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 17, no 3, p. 34-Article in journal (Refereed)
    Abstract [en]

    Theoretically, co-management provides a fruitful way to engage local residents in efforts to conserve and manage particular spaces of ecological value. However, natural resource management, and biodiversity conservation in particular, are faced with novel sets of complexities in the rapidly urbanizing areas of Cape Town, South Africa, and in the nexus between an apartheid past, informal settlements, remnant biodiversity patches, and urban poverty. Departing from such a dynamic social and ecological context, this article first provides an historical account of the decade-long comanagement process at Macassar Dunes, and then considers, through stakeholder perceptions, what are the successes and failures of the contested process. We find that comanagement at Macassar Dunes faces serious legitimacy, trust, and commitment issues, but also that stakeholders find common ground on education and awareness-raising activities. In conclusion we argue that the knowledge generated from case studies like this is useful in challenging and rethinking natural resource management theory generally, but specifically it is useful for the growing cities of the Global South. More case studies and a deeper engagement are needed with geographical theories on the urban fringe as possibility space, to help build a firm empirical base for theorizing comanagement at the fringes, i.e., at the intersection of poverty, socioeconomic inequality, and high biodiversity and ecological values.

  • 209.
    Graham, Marnie
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Exploring stakeholder perceptions of an urban protected area and associated co-management arrangements: Macassar Dunes, Cape Town, South Africa2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Within our cities the importance of urban green spaces such as forests, parks, wetlands, and protected areas are increasingly recognised for their contribution to human health and wellbeing, and in the provision of ecosystem services. Meanwhile, cities contain much social, cultural, economic, and environmental diversity, and natural resource management strategies for green areas need to account for the diversity of perspectives and conflict spaces that such urban diversity can encapsulate. Here, the empirical focus is on an urban protected area, Macassar Dunes, in Cape Town, bordered by vast informal and township settlement, and subject to a co-management arrangement for the last ten years between representatives of local residents, academic researchers, and conservation and planning authorities. This study examines the range of perceived ‘bridges’ and ‘barriers’ to co-management from the perspectives of stakeholders in the peak co-management body, the Maccasar Dunes Co-Management Association Management Committee (MDCA MC). This analysis finds the arrangements are perceived as both highly valuable and highly contested amongst MDCA MC stakeholders, with a wide array of bridges and barriers identified. In a complementary analysis the range of place meanings attached to Macassar Dunes within the MDCA MC are examined using the ‘sense of place’ concept. The contention of this thesis is that exploring issues of place through recognising places and their meanings as relational, political and contested can contribute to a co-management theory and practice which is more sensitive to the places through which it is enacted, and provide possibilities for understanding conflict in co-management arrangements.

  • 210.
    Granberg, Maria
    et al.
    Univ Gothenburg, Dept Marine Ecol, Kristineberg Marine Res Stn.
    Gunnarsson, Jonas
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hedman, Jenny
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Rosenberg, Rutger
    Univ Gothenburg, Dept Marine Ecol, Kristineberg Marine Res Stn.
    Jonsson, Per
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bioturbation-Driven Release of Organic Contaminants from Baltic Sea Sediments Mediated by the Invading Polychaete Marenzelleria neglecta.2008In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 42, no 4, p. 1058-1065Article in journal (Refereed)
    Abstract [en]

    Baltic Sea sediments are among the world’s most polluted regarding eutrophication and contamination. Eutrophication-induced hypoxia has caused depletion of bioturbating macrofauna in vast areas, producing laminated sediments. We investigated if reoxygenation and colonization by the invading deep-burrowing polychaete Marenzelleria neglecta may cause an augmented contaminant release from Baltic Sea sediments. Intact laminated sediment cores were exposed either to in situ hypoxia, reoxygenation, or reoxygenation combined with bioturbating M. neglecta. The release fluxes of particle-associated (NPart) and dissolved (NDiss) PCBs and chlorinated pesticide residues (POPs) were quantified (GC-ECD) after 85 d along with contaminant concentrations in sediment and biota. Lavoisier-based mass transfer coefficients (Kf) were calculated from NDiss. Sediment contaminant concentrations were high (ΣPCB7: 42–52 ng gsediment−1 dw) due to emissions from Stockholm. NDiss always exceeded NPart by an order of magnitude. Bioturbation enhanced NDiss and Kf from hypoxic sediments 0.7 – 3 times while reoxygenation alone had no significant effect. M. neglecta accumulated low amounts of contaminants but significantly stimulated aquatic release of bioavailable sequestered contaminants. Bioturbation should be included in aquatic contaminant fate models. We advise to consider quiescent pollutant sources and possible ecological shifts when aiming to restore eutrophicated aquatic environments.

  • 211.
    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.

  • 212.
    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.

  • 213. Gunderson, L
    et al.
    Folke, Carl
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Looking forward, looking back2007In: Ecology and Society, Vol. 12, no 1, p. no 32-Article in journal (Other academic)
  • 214.
    Gunnarsson, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Svensson, Ola
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kraftig ökning av Marenzelleria2012Other (Other (popular science, discussion, etc.))
  • 215.
    Gustafsson, Kerstin
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Blidberg, Eva
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Karlsson Elfgren, Irene
    Department of Ecology and Evolution/Limnology, Uppsala University.
    Hellström, Anna
    Department of Aquatic Science and Assessment, Swedish University of Agricultural Sciences.
    Kylin, Henrik
    Department of Aquatic Science and Assessment, Swedish University of Agricultural Sciences.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Direct and indirect effects of the fungicide azoxystrobin in outdoor brackish water microcosms2010In: Ecotoxicology, ISSN 0963-9292, E-ISSN 1573-3017, Vol. 19, no 2, p. 431-444Article in journal (Refereed)
    Abstract [en]

    The effects of the strobilurin fungicide azoxystrobin were studied in brackish water microcosms, with natural plankton communities and sediment. Two experiments were conducted: Experiment 1 (nominal conc. 0, 15 and 60 μg/L, 24-L outdoor microcosms for 21 days) and a second, follow-up, Experiment 2 (nominal conc. 0, 3, 7.5, 15 μg/L, 4-L indoor microcosms for 12 days). The microcosms represent a simplified brackish water community found in shallow semi-enclosed coastal areas in agricultural districts in the Baltic Sea region. Measured water concentrations of the fungicide (Experiment 1) were, on average, 83 and 62% of nominal concentrations directly after application, and 25 and 30% after 21 days, for the low and high dose treatments, respectively, corresponding to mean DT50-values of 15.1 and 25.8 days, for low and high dose treatments, respectively. In Experiment 1, direct toxic effects on calanoid copepods at both test concentrations were observed. Similarly, in Experiment 2, the copepod abundance was significantly reduced at all tested concentrations. There were also significant secondary effects on zooplankton and phytoplankton community structure, standing stocks and primary production. Very few ecotoxicological studies have investigated effects of plant protection products on Baltic organisms in general and effects on community structure and function specifically. Our results show that azoxystrobin is toxic to brackish water copepods at considerably lower concentrations than previously reported from single species tests on freshwater crustaceans, and that direct toxic effects on this ecologically important group may lead to cascade effects altering lower food webs and ecosystem functioning.

  • 216.
    Hajdu, S.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hällfors, S.
    Gromisz, S.
    Skjevik, A-T.
    Busch, S.
    Kownacka, J.
    Jurgensone, I.
    Olenina, I.
    Huseby, S.
    Andersson, A.
    Wasmund, N.
    Jaanus, A.
    Hällfors, G.
    Rintala, J-M.
    Majaneva, M.
    Blomster, J.
    Unusual phytoplankton event during winter-spring 2007-2008.2008Report (Other (popular science, discussion, etc.))
  • 217.
    Hajdu, Susanna
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    Höglander, Helena
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    Larsson, Ulf
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    Phytoplankton vertical distributions and composition in Baltic Sea cyanobacterial blooms2007In: Harmful Algae, Vol. 6, p. 189-205Article in journal (Refereed)
  • 218.
    Hajdu, Susanna
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Larsson, Ulf
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Andersson, A
    Huseby, S
    Skjevik, A-T
    Sommarens växtplanktonsamhälle har förändrats2007In: Havet, p. 47-50Article in journal (Other (popular science, discussion, etc.))
  • 219. Hallfors, Heidi
    et al.
    Hajdu, Susanna
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kuosa, Harri
    Larsson, Ulf
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Vertical and temporal distribution of the dinoflagellates Dinophysis acuminata and D. norvegica in the Baltic Sea2011In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 16, no 2, p. 121-135Article in journal (Refereed)
    Abstract [en]

    We investigated the distributions of the toxic dinoflagellates Dinophysis acuminata and D. norvegica in the brackish Baltic Sea, and found them to differ both regarding their seasonality and their vertical distribution. Dittophysis acuminata was considerably more abundant, especially in the Gulf of Finland, where we observed an August peak of 14 300 cells l(-1). It occurred in elevated abundances during or after periods of high phytoplankton biomass in early and late summer. Dinophysis norvegica was abundant during a shorter period, peaking one month after the first D. acuminata maximum. While D. norvegica probably is restricted by both salinity and temperature in the northern Baltic Sea, the more tolerant D. acuminata thrives. The results presented here expand the wide range of scenarios in which D. acuminata may bloom worldwide. Both species mainly formed population maxima either in the mixed surface waters or near the thermocline. Dinophysis acuminata usually occurred in the illuminated and nutrient-poor mixed surface layer, but in the presence of light and a nutricline it formed distinct subsurface peaks. Dinophysis norvegica was not as sensitive to darkness and predominantly formed subsurface peaks, even below the euphotic zone. These occurrences were promoted by shallow stratification, and the combination of a deep mixed layer and cool surface waters drew the D. norvegica population closer to the surface. When D. acuminata and D. norvegica co-occurred, their abundances peaked at different depths; this was observed even when both species formed maxima in the surface layer.

  • 220.
    Halling, Christina
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Wikström, Sofia A.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lilliesköld-Sjöö, Gustaf
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Mörk, Erik
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lundsor, Elisabeth
    Zuccarello, Giuseppe C.
    Introduction of Asian strains and low genetic variation in farmed seaweeds: indications for new management practices2013In: Journal of Applied Phycology, ISSN 0921-8971, E-ISSN 1573-5176, Vol. 25, no 1, p. 89-95Article in journal (Refereed)
    Abstract [en]

    Seaweed farming has a crucial role in the development of future sustainable mariculture. In the same time, spreading of introduced species or genotypes from farms may threaten local ecosystems. We analyzed a molecular marker (mitochondrial cox2-3 spacers) from cultivated and wild specimen of the widely farmed seaweeds Eucheuma and Kappaphycus, collected in Zanzibar on the African east coast where commercial farming was introduced in 1989. Genotypes of presumed Asian origin were found growing on coral reefs and drifting in seagrass meadows, indicating that genotypes introduced for farming have established successfully in the wild in Zanzibar. Only a very low number of genotypes, all of Asian origin, were found in the farms. This indicates a low accessible gene pool, which can limit the capacity for adaptation to changed conditions and disease resistance in the farming system. African genotypes were found in a few sites, showing the potential for future farming of native strains. The ecological effects of the Asian genotypes introduced to coral reefs should also be further investigated in order to evaluate the risk connected with further introductions of new foreign strains.

  • 221.
    Hansen, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Botany. Växtekologi.
    Robertson-Andersson, Deborah
    Troell, Max
    Department of Systems Ecology.
    Control of the herbivorous gastropod Fissurella mutabilis (Sow.) in a land-based integrated abalone-seaweed culture2006In: Aquaculture, Vol. 255, no 1-4, p. 384-388Article in journal (Refereed)
  • 222.
    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.

  • 223.
    Hansen, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Wikström, Sofia
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Axemar, Hanna
    Stockholm University, Faculty of Science, Department of Botany.
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Distribution differences and active habitat choices of invertebrates between macrophytes of different morphological complexity2011In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 45, no 1, p. 11-22Article in journal (Refereed)
    Abstract [en]

    This study explores: (1) whether the abundance of macroinvertebrates differs between macrophytes differing in both morphological complexity and tolerance to nutrient enrichment; (2) whether the distribution of invertebrates between macrophytes is due to active habitat choice; and (3) whether invertebrates prefer structurally complex to simple macrophytes. Macroinvertebrate abundance was compared between two common soft-bottom plants in the Baltic Sea that are tolerant to eutrophication, Myriophyllum spicatum and Potamogeton pectinatus, and one common plant that is sensitive to eutrophication, Chara baltica. Both field sampling and habitat choice experiments were conducted. We recorded higher total macroinvertebrate abundance on the structurally complex M. spicatum than on the more simply structured P. pectinatus and C. baltica, but found no difference in macroinvertebrate abundance between P. pectinatus and C. baltica. In accordance with the field results, our experiment indicated that the crustacean Gammarus oceanicus actively chose M. spicatum over the other macrophytes. Besides, we found that G. oceanicus actively preferred complex to simply structured artificial plants, indicating that the animal distribution was at least partly driven by differences in morphological complexity between plant species. In contrast, the gastropod Theodoxus fluviatilis did not make an active habitat choice between the plants. Our findings suggest that human-induced changes in vegetation composition can affect the faunal community. Increased abundance of structurally complex macrophytes, for example, M. spicatum, can result in increased abundance of macroinvertebrates, particularly mobile arthropods that may actively choose a more structurally complex macrophyte.

  • 224.
    Hansen, Joakim
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Wikström, Sofia
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kautsky, Lena
    Stockholm University, Faculty of Science, Department of Botany.
    Taxon composition and food-web structure in a morphometric gradient of Baltic Sea land-uplift bays2012In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 17, no 1, p. 1-20Article in journal (Refereed)
    Abstract [en]

    Shallow Baltic Sea bays undergo a process of morphometric isolation from the sea due to post-glacial land uplift. Recent studies have documented that both flora and fauna communities change along this gradient. Changes in taxon composition may in turn alter feeding ecology and trophic relationships. In addition, the relative importance of carbon from terrestrial sources may increase with bay isolation. In accordance with previous studies, we found a change in the community composition of both flora and fauna with bay isolation. Results of stable isotope analysis (δ13C, δ15N) suggested that epiphytes and periphyton are the major carbon sources for most benthic primary consumers, but that their importance in relation to angiosperms and charophytes decreased with bay isolation. The results also indicated that filter feeders utilize terrestrially derived carbon, but its importance could not be critically related to bay isolation. Trophic positions of the consumers were similar across the bay isolation gradient.

  • 225.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gösforskning i svenska Himmerfjärden.2008In: Fiskeritidskrift för Finland, Vol. 4/2008Article in journal (Other (popular science, discussion, etc.))
  • 226.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Vad har hänt med fiskbestånden i Östersjön?2008In: Fiskets kollaps utanför Nordamerika - vad kan Sverige och Europa lära?, 2008Chapter in book (Other (popular science, discussion, etc.))
  • 227.
    Hansson, Sture
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Dippner, Joachim W.
    Larsson, Ulf
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Climate effects on zooplankton biomasses in a coastal Baltic Sea area2010In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 15, no 3, p. 370-374Article in journal (Refereed)
    Abstract [en]

    To evaluate if climate influence zooplankton densities and dynamics in a coastal Baltic Sea area, we performed statistical analyses of two 12-13-year-long data series. The winter (December March) North Atlantic Oscillation index (NAO) was used as the independent variable and monthly biomasses of seven groups of zooplankton as the dependent variables. Most of the statistically significant correlations were obtained for the spring-early-summer period and they all indicate higher zooplankton biomasses after winters with high NAO values (mild winters). This supports results from other Baltic Sea studies, indicating that winter/spring climate is important to the early summer zooplankton community.

  • 228.
    Hansson, Sture
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    Hjerne, Olle
    Stockholm University, Faculty of Science, Department of Systems Ecology. marin ekologi.
    Harvey, C
    Kitchell, JF
    Cox, SP
    Essington, TE
    Managing Baltic Sea fisheries under contrasting production and predation regimes: ecosystem model analyses2007In: Ambio, Vol. 36, no 2-3, p. 259-265Article in journal (Refereed)
  • 229.
    Hedman, Jenny E
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Fate of contaminants in Baltic Sea sediment ecosystems : the role of bioturbation2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Aquatic sediments are of major importance for the cycling of environmental pollutants, acting as both sinks and secondary sources of contaminants to the ecosystem. Sediment-living organisms can affect the fate and transport of contaminants through activities like feeding and burrowing, collectively called bioturbation. Apart from high contaminant levels, the Baltic benthic ecosystem is affected by stressors such as eutrophication-induced anoxic conditions and invading alien species. The main objectives of this thesis were to determine the effects of bioturbation on contaminant fluxes in Baltic Sea sediments and to increase the understanding of how these other stressors act together upon contaminant fate in the benthic ecosystem.

    Bioturbation affected contaminants in a species-specific way. The native species Monoporeia affinis and Macoma balthica increased the incorporation of BDE-99 and Cd deposited on the sediment surface, enhancing their retention in the sediment. The invasive polychaete Marenzelleria sp. did not contribute to the incorporation of surface-deposited contaminants, however, significantly increased the release of contaminants back to the water column. Reoxygenation of anoxic laminated sediments and bioturbation by Marenzelleria increased the sediment-to-water flux of dissolved organic contaminants. When the bioturbation-driven release of PCB was compared to the release caused by physical sediment resuspension, results indicated that the continuous activities of benthic infauna can be just as, or even more, important than physical disturbance for the remobilization of sediment-bound contaminants. Bioaccumulation was significantly higher when contaminants were deposited associated to phytoplankton compared to lignin or sediment, suggesting that there are likely seasonal differences in the mobilization of contaminants in the benthic ecosystem.

    In summary, bioturbation is an important process influencing contaminant fate in Baltic Sea sediments, and the risk of remobilization of historically buried contaminants may increase with improved benthic redox conditions and the invasion of new deeper-digging species, such as Marenzelleria.

  • 230.
    Hedman, Jenny E.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Bradshaw, Clare
    Thorsson, Maria H.
    Gilek, Michael
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Fate of contaminants in Baltic Sea sediments: role of bioturbation and settling organic matter2008In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 356, p. 25-38Article in journal (Refereed)
    Abstract [en]

    This experimental study examined the interactive effects of bioturbation and settling organic matter (OM) on the fate (burial and remobilisation) of 2 surface-deposited contaminants in Baltic Sea sediment: the metal Cd and a hydrophobic organic pollutant, the flame retardant BDE-99. Three macrofaunal species with diverse feeding and bioturbation strategies were used: the amphipod Monoporeia affinis, the clam Macoma balthica and the polychaete Marenzelleria spp. Radiolabelled contaminants were added to the sediment surface in association with 3 different OM types: (1) phytoplankton, (2) terrestrial lignin and (3) Baltic sediment. Bioturbation by all species increased the retention of both contaminants in the sediment, most effectively M. affinis and M. balthica. A decoupled transport of Cd and BDE-99 by Marenzelleria was observed. Generally, Marenzelleria buried the highest amount of Cd into the sediment but also caused the highest remobilisation to the water, indicating an effective transport of (soluble) Cd over the sediment-water interface via bio-irrigation. Lack of the highly hydrophobic and mainly particle-associated BDE-99 below the sediment surface suggests that Marenzelleria caused no significant particle mixing. The addition of various OM types significantly affected the distribution of Cd, but not of BDE-99. There was an interactive effect between bioturbation (species) and OM type, generally showing an increased burial and release of Cd when associated with phytoplankton in the presence of Marenzelleria. Our results emphasise the importance of understanding the complex interactions between ecological (e.g. infaunal feeding and bioturbation activities) and physiochemical processes (contaminant speciation and sorption kinetics) when assessing the fate of contaminants in aquatic ecosystems.

  • 231. Hedman, Jenny E.
    et al.
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Samuelsson, Göran
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gilbert, Franck
    Particle reworking and solute transport by the sediment-living polychaetes Marenzelleria neglecta and Hediste diversicolor2011In: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 407, no 2, p. 294-301Article in journal (Refereed)
    Abstract [en]

    This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind.m(-2)) and Hediste diversicolor (2 g ww, 800 ind.m(-2)) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient D(b) and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient D(a). The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). D(b) did not differ between the two species (2.4 x 10(-3) cm(2) d(-1)) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y(-1) for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min(-1) for H. diversicolor and 0.003 mL min(-1) for M. neglecta, corresponding to an area-specific rate of ca. 12 L m(-2) d(-1) at the used densities. D(a) did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.

  • 232.
    Hedman, Jenny E
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gunnarsson, Jonas S
    Samuelsson, Göran
    Gilbert, Franck
    Sediment particle reworking and solute transport by two common polychaetes in the Baltic Sea, Nereis diversicolor and Marenzelleria sp.Manuscript (Other academic)
  • 233.
    Hedman, Jenny E
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Stempa Tocca, Julia
    Gunnarsson, Jonas S
    Remobilization of PCB from Baltic Sea sediment: comparing the roles of bioturbation and physical resuspension2009In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 28, no 11, p. 2241-2249Article in journal (Refereed)
    Abstract [en]

    The release of a 14C-labeled trichlorobiphenyl compound ([14C]PCB 32) from sediment to water was quantified weekly in a 30-d microcosm experiment with recirculating water. Two modes of bioturbation-driven polychlorinated biphenyl (PCB) release—bioturbation by the amphipod Monoporeia affinis (a particle biodiffuser) and bioturbation by the polychaete Marenzelleria sp. (a bioirrigator)—were compared to the PCB release caused by physical resuspension of the sediment generated by a motor-driven paddle used twice a week. Bioturbation by the amphipod M. affinis caused a significantly higher remobilization of both particle-associated PCB (PCBpart) and dissolved PCB (PCBdiss) than the other treatments. Bioturbation by Marenzelleria sp. and physical resuspension caused a similar release of PCBdiss despite a significantly higher amount of total suspended solids in the water column after physical resuspension. In all treatments, the release of PCBdiss was more than one order of magnitude higher than that of PCBpart, indicating a significant potential route of exposure for pelagic organisms, such as fish, to the most bioavailable PCB form. Calculated mass-transfer coefficients (0.3–1.3 cm/d) correspond to previously reported values for trichlorinated PCBs. The present results indicate that biological reworking of sediments can be just as, or even more, important than physical resuspension for the remobilization of sediment-bound contaminants.

  • 234.
    Hedman, Jenny E.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Tocca, Julia Stempa
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Remobilization of Polychlorinated Biphenyl from Baltic Sea Sediment: Comparing the Roles of Bioturbation and Physical Resuspension2009In: Environmental Toxicology and Chemistry, ISSN 0730-7268, E-ISSN 1552-8618, Vol. 28, no 11, p. 2241-2249Article in journal (Refereed)
    Abstract [en]

    The release of a C-14-labeled trichlorobiphenyl compound ([C-14]PCB 32) from sediment to water was quantified weekly in a 30-d microcosm experiment with recirculating water. Two modes of bioturbation-driven polychlorinated biphenyl (PCB) release-bioturbation by the amphipod Monoporeia affinis (a particle biodiffuser) and bioturbation by the polychaete Marenzelleria sp. (a bioirrigator)-were compared to the PCB release caused by physical resuspension of the sediment generated by a motor-driven paddle used twice a week. Bioturbation by the amphipod M. affinis caused a significantly higher remobilization of both particle-associated PCB (PCBpart) and dissolved PCB (PCBdiss) than the other treatments. Bioturbation by Marenzelleria sp. and physical resuspension caused a similar release of PCBdiss despite a significantly higher amount of total suspended solids in the water column after physical resuspension. In all treatments, the release of PCBdiss was more than one order of magnitude higher than that of PCBpart, indicating a significant potential route of exposure for pelagic organisms, such as fish, to the most bioavailable PCB form. Calculated mass-transfer coefficients (0.3-1.3 cm/d) correspond to previously reported values for trichlorinated PCBs. The present results indicate that biological reworking of sediments can be just as, or even more, important than physical resuspension for the remobilization of sediment-bound contaminants.

  • 235.
    Hellström, Ann Micaela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Benzie, J. A. H.
    Robustness of size measurements in soft corals2011In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 30, no 3, p. 787-790Article in journal (Refereed)
    Abstract [en]

    Accurate colony size measurement in soft-bodied sessile aquatic invertebrates is more difficult than in hard corals because of the variable state of the hydroskeleton in the former. The present study examined variation in colony height, oral disc diameter and basal circumference in three species of soft coral of different morphological types (Sarcophyton elegans, Sinularia flexibilis and Dendronephthya sp.) over a 24-h period. Individual colonies changed considerably in size over this period. Coefficients of variation for height measurements and oral disc were 0.09–0.36 and 0.08–0.28, respectively, but were only 0.02–0.09 for basal circumference, in all three species. Measurements of basal circumference in the field showed the highest correlation with colony biomass (volume after water displacement in formalin) confirming basal circumference to be a sound measure of colony size in repeated measurement studies.

  • 236.
    Hellström, Micaela
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Sex and symbionts: New discoveries in local and regional patterns of coral ecology and reproduction2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Coral reefs belong to the most diverse and the most threatened ecosystems on earth. Anthropogenic stressors and climate change have led to mortalities at levels unprecedented in modern times. The aims of this thesis are to investigate aspects of the corals’ ability to reproduce, disperse, adapt and survive. Papers I-III study reproduction in a common soft coral species, Sarcophyton elegans, with previously unknown reproductive modes. Paper IV investigates genetic distribution of coral-symbiont associations in Galaxea fascicularis focusing on adaptation to the environment along the coastline of Vietnam.

    Sarcophyton  elegans is a gonochoric broadcast spawner with a 1:1 sex ratio. Reproduction is strictly size dependent. Oogenesis takes 19-24 months, with a new cycle commencing every year. Spermatogenesis takes 10-12 months. The majority of gametes were released during the annual austral mass spawning event after full moon in November, but spawning also occur between August and February. The polyps at the outer edge of the colonies released their gametes first, followed by polyps situated closer to the center during subsequent months. Colonies upstream in the prevailing current spawn earlier than those downstream. The colonies were arranged in clusters of alternating males and females, which spawned simultaneously and were of the same genotype. Fission and buddying is a common mode to expand locally. Additionally, females undergoing fission divided into the most fecund size classes.

    The G. fascicularis and their associated symbionts were not genetically coupled to each other but to environmental factors. The host displayed an inshore-offshore zonation, with higher diversity offshore. The D1a symbiont exhibited an inshore- offshore zonation. In contrast; the 5 different C symbiont types showed a latitudinal distribution gradient, which shifted in dominance north to south. The study highlights the importance of protecting resilient coral and algal genotypes in stressed areas and the need to understand reproductive modes for coral conservation.

  • 237.
    Hellström, Micaela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gross, Susanna
    Hedberg, Nils
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Faxneld, Suzanne
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Cuong, C. T.
    Nguyen Ngai, D.
    Huong, Le Lan
    Grahn, M.
    Benzie, J.A.H.
    Tedengren, Michael
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Symbiodinium spp. diversity in a single host species, Galaxea fascicularis, Vietnam: Impact of environmental factors, host traits, and diversity hot spotsManuscript (preprint) (Other academic)
    Abstract [en]

    We determined the distribution of zooxanthellate ITS2 types within one broadcast spawning coral species,

    Galaxea fascicularis with horizontal symbiont uptake, in both inshore and offshore reef habitats over a 3200 km range along the coast of Vietnam, covering 11 degrees of latitude. Host traits (mtDNA genotype) and environmental factors (visibility, sea surface temperatures and Chlorophyll a derived from satellite data, regional measures of coral species diversity and distance from land (inshore/offshore)) were measured to test whether symbiont type distribution was determined by host characteristics or by environmental factors. The G. fascicularis and their associated symbionts were not genetically coupled to each other but to environmental factors The host displayed an inshore-offshore zonation, with higher diversity offshore. The D1a symbiont exhibited an inshore- offshore zonation. In contrast; the 5 different C symbiont types showed a latitudinal distribution gradient, which shifted in dominance north to south. We found regional differences in symbiont type; these were related to environmental differences and not to genetic characteristics in the coral G. fascicularis.

  • 238.
    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.

  • 239.
    Hellström, Micaela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Kavanagh, K.D.
    Mallick, S.
    Benzie, J. A. H.
    Mode of vegetative reproduction and genetic identification of spawning groups, in the soft coral Sarcophyton elegans, Lizard Island, Northern Great Barrier ReefManuscript (preprint) (Other academic)
  • 240. Hillebrand, Helmut
    et al.
    Soininen, Janne
    Snoeijs, Pauline
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Warming leads to higher species turnover in a coastal ecosystem2010In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 16, no 4, p. 1181-1193Article in journal (Refereed)
    Abstract [en]

    The responses of ecological communities and ecosystems to increased rates of environmental change will be strongly influenced by variation in the diversity of community composition. Yet, our understanding of how diversity is affected by rising temperatures is inconclusive and mainly based on indirect evidence or short-term experiments. In our study, we analyse the diversity and species turnover of benthic epilithic communities within the thermal flume of a nuclear power plant at the Swedish coast. This flume covers the range of predicted future temperature rises. Species composition was significantly different between control sites and sites with higher temperatures. We found that temperature had little effect on the number of species in three functional groups (macroinvertebrates, benthic diatoms, and macrophytes, which here comprise multicellular algae and macroscopic colonies of unicellular algae and cyanobacteria), neither at single sampling dates nor summed for the entire observation year. However, species turnover significantly increased with increasing temperature for diatoms, macrophytes and invertebrates. Different temperature regimes resulted in significantly different species composition and indicator species. Thus, increasing temperatures in the thermal flume increased temporal beta-diversity and decreased compositional stability of communities, although observed richness did not change at any point in time. We highlight the need to investigate the consequences of such declines in compositional stability for functional stability of ecosystem processes.

  • 241. Hinton, T. G.
    et al.
    Garnier-Laplace, J.
    Vandenhove, H.
    Dowdall, M.
    Adam-Guillermin, C.
    Alonzo, F.
    Barnett, C.
    Beaugelin-Seiller, K.
    Beresford, N. A.
    Bradshaw, Clare
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Brown, J.
    Eyrolle, F.
    Fevrier, L.
    Gariel, J. -C
    Gilbin, R.
    Hertel-Aas, T.
    Horemans, N.
    Howard, B. J.
    Ikaheimonen, T.
    Mora, J. C.
    Oughton, D.
    Real, A.
    Salbu, B.
    Simon-Cornu, M.
    Steiner, M.
    Sweeck, L.
    Vives i Batlle, J.
    An invitation to contribute to a strategic research agenda in radioecology2013In: Journal of Environmental Radioactivity, ISSN 0265-931X, E-ISSN 1879-1700, Vol. 115, p. 73-82Article in journal (Refereed)
    Abstract [en]

    With intentions of integrating a portion of their respective research efforts into a trans-national programme that will enhance radioecology, eight European organisations recently formed the European Radioecology ALLIANCE (www.er-alliance.org). The ALLIANCE is an Association open to other organisations throughout the world with similar interests in promoting radioecology. The ALLIANCE members recognised that their shared radioecological research could be enhanced by efficiently pooling resources among its partner organizations and prioritising group efforts along common themes of mutual interest. A major step in this prioritisation process was to develop a Strategic Research Agenda (SRA). An EC-funded Network of Excellence in Radioecology, called STAR (Strategy for Allied Radioecology), was formed, in part, to develop the SRA. This document is the first published draft of the SRA. The SRA outlines a suggested prioritisation of research topics in radioecology, with the goal of improving research efficiency and more rapidly advancing the science. It responds to the question: What topics, if critically addressed over the next 20 years, would significantly advance radioecology? The three Scientific Challenges presented within the SRA, with their 15 associated research lines, are a strategic vision of what radioecology can achieve in the future. Meeting these challenges will require a directed effort and collaboration with many organisations the world over. Addressing these challenges is important to the advancement of radioecology and in providing scientific knowledge to decision makers. Although the development of the draft SRA has largely been a European effort, the hope is that it will initiate an open dialogue within the international radioecology community and its stakeholders. This is an abbreviated document with the intention of introducing the SRA and inviting contributions from interested stakeholders. Critique and input for improving the SRA are welcomed via a link on the STAR website (www.star-radioecology.org).

  • 242.
    Hogfors, Hedvig
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    During summer, the Baltic Sea is subjected to the world’s largest cyanobacterial blooms. These blooms are linked to eutrophication and raise many questions concerning their effects on the ecosystem. To understand their impacts on the food web dynamics, it is essential to assess growth responses of grazers to these cyanobacteria. In the northern Baltic proper, copepods are the most important herbivores providing an essential link between the primary producers and higher trophic levels. In this Thesis, Papers I & II evaluate methods to estimate copepod growth in response to feeding conditions in situ. The most conspicuous diazotrophic filamentous cyanobacterium in the Baltic Sea is Nodularia spumigena, a producer of nodularin which is highly toxic to vertebrates, yet its ecological role is largely unknown. In Paper III, reciprocal interactions between cyanobacteria, sympatric algae and copepods are studied. The results suggest that nodularin is likely involved in allelopathic interactions, but it is not an inducible defense against grazers. Furthermore, the results of Papers IV & V, indicate that natural assemblages of N. spumigena and Anabaena spp. may support copepod reproduction and that total diazotrophic filamentous cyanobacteria appear to provide a beneficial feeding environment for the feeding stages of copepod nauplii, most probably by stimulating the microbial communities that nauplii feed upon. Since cyanobacterial blooms are projected to increase due to global climate change, the combined effects of toxic cyanobacteria, ocean acidification and global warming predicted for year 2100 are further investigated on copepods in Paper IV. Taken together, these studies indicate that filamentous diazotrophic cyanobacteria contribute to sustaining secondary productivity and have potential implications of management practices with respect to combating eutrophication, global climate change and sustaining fish feeding conditions.

  • 243.
    Hogfors, Hedvig
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Holmborn, Towe
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hajdu, Susanna
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Does female RNA content reflect viable egg production in copepods?: A test with the Baltic copepod Acartia tonsa2011In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 33, no 9, p. 1460-1463Article in journal (Refereed)
    Abstract [en]

    Biomarkers are very useful for in situ assessments of zooplankton growth. In particular, RNA-based methods have been developed to estimate egg production in copepods. However, RNA-growth relationships can potentially depend on a variety of factors, such as egg quality. This study shows that in Acartia tonsa, female RNA-content reflects egg production irrespective of egg viability, implying that this growth proxy is not applicable for recruitment studies if the proportion of viable eggs fluctuates widely.

  • 244. Holeton, Claire
    et al.
    Lindell, Kristin
    Holmborn, Towe
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hogfors, Hedvig
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Decreased astaxanthin at high feeding rates in the calanoid copepod Acartia bifilosa2009In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 31, no 6, p. 661-668Article in journal (Refereed)
    Abstract [en]

    In marine food webs, copepods are the major producers of a carotenoid pigment astaxanthin, which is an important antioxidant. The availability of astaxanthin for higher trophic levels can be affected by changes in phytoplankton stocks and copepod feeding; however, the functional relationship between food availability and astaxanthin production is poorly understood. We hypothesized that with a given food type and quality, astaxanthin content in copepods is positively related to feeding and egg production rates. The hypothesis was tested by measuring astaxanthin accumulation in concert with ingestion and egg production rates in the copepod Acartia bifilosa exposed to different algal concentrations (Tetraselmis suecica; 0 to 1200 μg C L−1). Egg production and ingestion rates increased with increasing food availability and reached a plateau at ≥400–600 μg C L−1. In contrast, increasing accumulation of astaxanthin with increasing food availability was observed only at concentrations ≤150 μg C L−1. Contrary to our hypothesis, at 600–1200 μg C L−1 copepods had maximal ingestion and egg production rates, but low astaxanthin contents. It is suggested that this low accumulation of astaxanthin at high food concentrations results from a food-dependant decrease in assimilation efficiency. These findings are important for the understanding of astaxanthin dynamics within marine food webs, where increases in phytoplankton biomass may translate to a trade-off between zooplankton quantity and its nutritional quality for zooplanktivores.

  • 245.
    Holliland, Per B.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Trophic interactions and behaviour: Studies relevant to a Baltic Sea biomanipulation2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The main theme of this thesis is the interactions of animals with the environment and each other. The thesis was written within the framework of a biomanipulation project “Pikeperch in Himmerfjärden”. With the aim to investigate possible trophic pit-falls, give the manipulation the best possible start, and find ways to monitor the progression of the manipulation. In Paper I the diet of the invader cladoceran Cercopagis pengoi is analysed with stable isotopes; conducted prior to stocking. C.pengoi has a preference for large copepods, indicating possible competition with fish. Paper II investigates the behavioural differences between pikeperch fingerlings reared in different environments (pond vs. tank). Results suggest that fish reared in semi-natural ponds are more likely to survive directly after stocking. In Paper III and IV, the diel vertical migrations (DVM) of copepods are in focus. In Paper III the migrations of two copepod species: Acartia spp. and Eurytemora affinis are studied over season and life stage. The amplitude of migration was found to increase with ontogeny for both species, indicating evasion of visual predators. Paper IV examines the varying migratory patterns of adult female E. affinis finding that these animals migrate more actively when feeding conditions deteriorate and growth decreases. The overall conclusions of the thesis are that behavioural, not only direct trophic interactions are key when studying ecosystems.

  • 246.
    Holliland, Per B.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Ahlbeck, Ida
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Westlund, Erica
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Hansson, Sture
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Ontogenetic and seasonal changes in diel vertical migration amplitude of the calanoid copepods Eurytemora affinis and Acartia spp. in a coastal area of the northern Baltic Proper2012In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 34, no 4, p. 298-307Article in journal (Refereed)
    Abstract [en]

    We studied diel vertical migration (DVM) of the six copepodite stages of two of the most abundant crustacean zooplankton in the Baltic Sea, the calanoid copepods Eurytemora affinis and Acartia spp. The study was conducted monthly from May through October in a bay in the northwestern Baltic proper. Fish biomass, phytoplankton abundance and temperature were obtained in conjunction with the zooplankton sampling. Both copepod species performed DVM. With the exception of females, all E. affinis copepodite stages performed migrations of over 10 m with only a slight increase with the copepodite stage. Adult female E. affinis remained at depth with only slight upward movement at night. In Acartia spp., DVM amplitude increased with stage and size, suggesting an ontogenetic shift in behaviour; although they had a less pronounced DVM than E. affinis. Although DVM amplitude increased with size, indicative of visual predation, fish biomass did not correlate with the amplitude of DVM. However, fish were present throughout the study period. We surmise that these ontogenetic shifts in behaviour are due to size increase and therefore visibility to predators and that the difference in DVM between the species may well be a result of physiological differences and reproductive strategy.

  • 247.
    Holliland, Per B.
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Holmborn, Towe
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Assessing diet of the non-indigenous predatory cladoceran Cercopagis pengoi using stable isotopes2012In: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 34, no 5, p. 376-387Article in journal (Refereed)
    Abstract [en]

    In the Baltic Sea, the predatory cladoceran Cercopagis pengoi is a non-indigenous species that has potential to compete for mesozooplankton with pelagic zooplanktivorous fish. To understand the extent of diet overlap with these fishes in a coastal area of the northern Baltic proper, we studied the feeding of C. pengoi using stable C-13 and N-15 isotope signatures of the predator and possible prey. Feasible combinations of sources were estimated in two ways: (i) with the IsoSource mixing model, and (ii) temporal-tracking analysis. Further, contribution of different prey was related to ambient zooplankton composition to gauge selectivity. The modelling results indicate that C. pengoi is an opportunistic generalist predator with a positive selection towards older copepodites (CIVVI) of Acartia spp. and Eurytemora affinis, which also have the greatest contribution to its diet. Positive selection towards podonid Cladocera is also likely. In contrast, evidence for extensive feeding on microzooplankton was inconclusive, and bosminids were not found to be an important prey in the zooplankton assemblages studied. As the derived diet of C. pengoi overlaps greatly with that of zooplanktivorous fish, food competition between these zooplanktivores is possible.

  • 248.
    Holliland, Per
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Holmborn, Towe
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Assessing diet of the non-indigenous predatory cladoceran Cercopagis pengoi using stable isotopesManuscript (preprint) (Other (popular science, discussion, etc.))
  • 249.
    Holliland, Per
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Motwani, Nisha
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Ogonowski, Martin
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Gorokhova, Elena
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Growth, reproduction and genetic variation : testing causes of variable diel vertical migration in the copepod Eurytemora affinisManuscript (preprint) (Other academic)
  • 250.
    Holmborn, Towe
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Zooplankton growth and trophic linkages: Implications for fish feeding conditions in the Baltic Sea2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this Thesis was to improve our understanding and assessment of feeding conditions for zooplanktivorous fish in the Baltic Sea.

    We investigated (papers I, II) the usefulness of biochemical proxies for assessments of growth and metabolic rates in the dominant Baltic copepod Acartia bifilosa. A predictive model (paper I) for egg production rate (EPR), based on body size, RNA content, and water temperature, was established using females of different geographical origin. This model demonstrates the usefulness of RNA content as a proxy for growth in zooplankton and, together with abundance data, it could be used to evaluate fish feeding conditions. Further (paper II), using A. bifilosa exposed to a food gradient, we evaluated responses of physiological rates and other biochemical proxies for growth and established correlations between physiological and biochemical variables. EPR and ingestion rate were most significantly correlated with RNA content. As assayed variables saturated at different food concentrations, food availability may affect assessments of physiological rates using proxies. In paper III, we explored the effect of high EPR and ingestion rate on astaxanthin content in A. bifilosa. We found that the astaxanthin content decreased at high feeding rates, most likely due to decreased assimilation efficiency. This may impact the quality of zooplankton as prey.

    The invasion of Cercopagis pengoi, a zooplanktivorous cladoceran, has altered the trophic linkages in the Baltic Sea food web. In paper IV, we evaluated the feeding of zooplanktivorous fish on C. pengoi and found that irrespective of size both herring and sprat feed on it, with large herring being more selective. In turn, C. pengoi feeds mainly on older copepods (paper V), which are acknowledged important in fish nutrition. These results indicate that C. pengoi may compete with fish due to the diet overlap.

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