135 research outputs found

    Trade-offs between storage and survival affect diapause timing in capital breeders

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    Blue mussels in western Norway have vanished where in reach of crawling predators

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    Blue mussels (Mytilus spp.) are declining around the world. In western Norway, they have widely disappeared from rocky shores but still thrive on floating structures. Other refugia are cracks in rocks, exposed sites, and low-salinity habitats. Climate change, pollution, disease, parasites, hybridization, and failed recruitment might not alone be able to create such distribution patterns. We hypothesized that crawling predators that are unable to reach floating structures may drive the present decline in western Norway. A known crawling predator without a pelagic stage and sensitive to low salinity and high wave action is the dogwhelk Nucella lapillus. Tributyltin (TBT) contained in anti-fouling paint rendered this snail sterile, but TBT is now banned, and populations are recovering rapidly. We first surveyed floating structures together with nearby rocky shores for blue mussels and dogwhelks. Blue mussels were present on all surveyed floating docks (65% area covered), but only on 18% of rocky shores (≤5% area covered). Similarly, blue mussels were found on 83% of tree branches suspended in water without bottom contact, but only on 1% when branches touched the seafloor. We then conducted a predator exclusion experiment with caged blue mussels (40-80 mm). In cages, mortality due to factors other than dogwhelks was extremely low (<1%) and confirmed that blue mussels continue to thrive when out of reach of predators. If dogwhelks or other crawling predators such as crabs or sea stars created the observed distribution pattern, then environmentally friendly mariculture with blue mussels growing on rafts and longlines might still have high potential in Norway. ytilus · Dogwhelk · Nucella lapillus · Foundation species · Invertebrate predators · Population decline · Predator recovery · Woody debris · Coarse woody habitatBlue mussels in western Norway have vanished where in reach of crawling predatorspublishedVersio

    Energy content of krill and amphipods in the Barents Sea from summer to winter: variation across species and size

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    Arctic zooplankton develop large energy reserves, as an adaptation to strong seasonality, making them valuable prey items. We quantified the energy content (kJ g−1 dry weight) of abundant krill (arcto-boreal, Thysanoessa inermis and boreal, Meganyctiphanes norvegica) and amphipods (Arctic, Themisto libellula and sub-Arctic-boreal, Themisto abyssorum) in the Barents Sea in late summer (August) and early winter (December). Variation in energy content was attributed to species-specific traits and body size categories, the latter in part as a proxy for ontogeny. T. inermis had the highest energy content, (Aug: 26.8 ± 1.5 (SD) kJ g−1) and remained similar from summer to winter. Energy content increased in M. norvegica and decreased in both amphipod species, with the lowest energy content being in T. abyssorum (Dec: 17.8 ± 0.8 kJ g−1). The effect of body size varied between species, with energy content increasing with size in T. inermis and T. libellula, and no change with size in M. norvegica and T. abyssorum. The reproductive stages of T. libellula differed in energy content, being highest in gravid females. Energy content varied with species’ dependence on energy storage. Our findings highlight how phylogenetically and morphologically similar prey items cannot necessarily be considered equal from a predator´s perspective. Energetically, the northern T. inermis was higher quality compared to the more southern M. norvegica, and mostly so during summer. Ecological models and management strategies should consider such variation in prey quality, especially as Arctic borealization is expected to change species composition and the energetic landscape for predators.publishedVersio

    Nesting synchrony and clutch size in migratory birds: Capital versus income breeding determines responses to variable spring onset

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    Synchronous reproduction of birds has often been explained by benefits from nesting together, but this concept fails to explain observed intraspecific variation and climate-mediated changes of breeding synchrony. Here, we present a theoretical model of birds that store resources for reproduction (capital breeders) to show how breeding synchrony, clutch size, and offspring recruitment respond to changes in timing of first possible breeding date. Our approach is based on individual fitness maximization when both prebreeding foraging and offspring development are time constrained. The model predicts less synchronous breeding, smaller clutch size, and higher chances for offspring recruitment in capital breeding birds that advance their nesting. For contrast, we also show that birds that need to acquire resources during egg laying (income breeders) do not change nesting synchrony but increase clutch size along with earlier breeding. The prediction of stronger nesting synchronization of capital breeders in years with late nesting onset is confirmed by empirical data on breeding synchrony of a high-latitude capital breeding sea duck, the common eider (Somateria mollissima). We predict that in warming high-latitude ecosystems, bird species that depend on stored reserves for reproduction are expected to desynchronize their nesting.publishedVersio

    Experimental icing affects growth, mortality, and flowering in a high Arctic dwarf shrub

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    Acknowledgments This study was funded by the Research Council of Norway (POLARPROG grant 216051; SFF-III grant 223257/F50) and Svalbard Environmental Protection Fund (SMF grant 13/74). We thank Mathilde Le Moullec for helping with the fieldwork and the Norwegian Meteorological Institute for access to weather data.Peer reviewedPublisher PD

    What we do in the dark: Prevalence of omnivorous feeding activity in Arctic zooplankton during polar night

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    During the productive polar day, zooplankton and sea-ice amphipods fulfill a critical role in energy transfer from primary producers to higher trophic-level species in Arctic marine ecosystems. Recent polar night studies on zooplankton and sea-ice amphipods suggest higher levels of biological activity than previously assumed. However, it is unknown if these invertebrates maintain polar night activity on stored lipids, opportunistic feeding, or a combination of both. To assess how zooplankton (copepods, amphipods, and krill) and sea-ice amphipods support themselves on seasonally varying resources, we studied their lipid classes, fatty acid compositions, and compound-specific stable isotopes of trophic biomarker fatty acids during polar day (June/July) and polar night (January). Lipid storage and fatty acid results confirm previously described dietary sources in all species during polar day. We found evidence of polar night feeding in all species, including shifts from herbivory to omnivory. Sympagic-, pelagic-, and Calanus spp.-derived carbon sources supported zooplankton and sea-ice amphipods in both seasons. We provide a first indication of polar night feeding of sea-ice amphipods in the pelagic realm

    Lipid sac area as a proxy for individual lipid content of arctic calanoid copepods

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    We present an accurate, fast, simple and non-destructive photographic method to estimate wax ester and lipid content in single individuals of the calanoid copepod genus Calanus and test this method against gas-chromatographic lipid measurements

    Investigation of new brominated and organophosphorous flame retardants in Svalbard benthic marine food web; FlammePlank

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    Project manager Pernilla CarlssonThe aim of this pilot-study was to use silicone rubber-based passive samplers to measure novel brominated flame retardants (nBFRs), polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) in seawater and air around Longyearbyen as well as investigate the presence of those compounds in sediment and biota (amphipods, Gammarus spp.) nearby Longyearbyen. Passive samplers require no electricity and provide an integrated picture of the levels of the targeted compounds over time. The results were combined with the sampled sediment and Gammarus spp. to assess concentrations in the environment. Out of all substances under study, PBDE-47 and -99, α- and β- tetrabromoethylcyclohexane (TBECH), syn- and anti-DP were detected in all investigated matrices. Freely dissolved water concentrations of ΣDPs (3 pg/L) were in line with recent Arctic studies, while ΣPBDEs (3 pg/L) were comparable to urban rivers in southern Norway. Nevertheless, for some compounds, especially the lighter and most volatile ones, long-range transport is most likely a more important contribution to observed levels than local sources. For other compounds, e.g. PBDEs, local sources might still play a role for the load of contaminants into the surrounding environment. The present study is the first to report a suit of nBFRs and DPs in Arctic benthic fauna. Many of the nBFRs and DPs were detected in sediment and in the amphipods. We recommend further studies with respect to measurements of concentrations over time, and in other species as well, to better understand whether the nBFRs and DPs are common in the marine environment on Svalbard. We recommend that local sources of flame retardants in remote areas receive more attention in the future.Svalbard miljøvernfondpublishedVersio

    Spatio-temporal dynamics in microalgal communities in Arctic land-fast sea ice

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    Sea ice microalgae are an important source of energy for the polar marine food web, representing the primary carbon source prior to pelagic phytoplankton blooms. Here we investigate community dynamics of sea ice microalgal communities in land-fast sea ice across six different fjords in high-Arctic Svalbard, Norway, during Spring (April – May). We found that light (0.1 – 23% incoming PAR / 0.1 – 193 μmol photons m-2s -1) played a central role in determining community composition, with more diverse assemblages observed in sites with more light transmitted to the bottom ice community. In April, microalgal assemblages were similar when under-ice light transmittance was similar, independent of geographical location, however this light-derived separation of community structure was not evident in May. At all sites, assemblages were dominated by pennate diatoms, with the most abundant taxon being Nitzschia frigida. However, with increasing under-ice light transmittance, we saw an increase in the relative abundance of Dinophyceae, Navicula spp. and Thalassiosira spp.. A positive relationship between light and δ13C enrichment and C:N ratios in the ice algal biomass demonstrated the effect of light on the biochemical composition of ice algae. Light did not correlate with cell abundance or chlorophyll a concentration. With anticipated changes to Arctic sea ice extent and snow cover as a result of climate change, we will see shifts in the light transmitted to the bottom ice community. These shifts, whether caused by reduced light transmittance from increased snow cover or increased light transmittance from thinning ice, snow depth or increased rainfall, will likely alter sea ice microalgal community composition, which in turn, may influence the success of secondary production and biogeochemical cycling in polar waterspublishedVersio
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