253 research outputs found
RaudvikaSvalbard2011_Varpe.mp4
No full textA 10-minute video illustrating the behaviour (e.g., diving, resting and social interactions) of black guillemots (Cepphus grylle) aggregated at a sea-ice ice edge in Raudvika, Kongsfjorden, Svalbard, 22 June 2011. (Filmed by Øystein Varpe.)
Part of the Supplementary material for: Varpe Ø. & Gabrielsen G.W. 2022. Aggregations of foraging black guillemots (Cepphus grylle) at a sea-ice edge in front of a tidewater glacier. Polar Research 41.
Correspondence: Øystein Varpe, University of Bergen, Department of Biological Sciences, P.O. Box 7803, NO-5020 Bergen, Norway. E-mail: [email protected] </p
Sea-ice Community Composition Data analysed in: Rebecca Duncan, Janne E. Søreide, Øystein Varpe, Józef Wiktor, Vanessa Pitusi, Elaine Runge, Katherina Petrou, 2023, "<b>Spatio-temporal dynamics in microalgal communities in Arctic land-fast sea ice".</b>
No full textSea-ice Protist Community Composition Data analysed in: Rebecca Duncan, Janne E. Søreide, Øystein Varpe, Józef Wiktor, Vanessa Pitusi, Elaine Runge, Katherina Petrou, 2023, "Spatio-temporal dynamics in microalgal communities in Arctic land-fast sea ice".</p
Diel and seasonal vertical migrations of high-latitude zooplankton: knowledge gaps and a high-resolution bridge
No full textDoctoral thesis (PhD) – Nord University, 2017publishedVersio
Interannual variability in key zooplankton species in the North-East Atlantic: an analysis based on abundance and phenology
No full textDoctoral thesis (PhD) – Nord University, 2017publishedVersio
Ecosystem model intercomparison of under-ice and total primary production in the Arctic Ocean
No full textPrevious observational studies have found increasing primary production (PP) in response to declining sea ice cover in the Arctic Ocean. In this study, under-ice PP was assessed based on three coupled ice-ocean-ecosystem models participating in the Forum for Arctic Modeling and Observational Synthesis (FAMOS) project. All models showed good agreement with under-ice measurements of surface chlorophyll-a concentration and vertically integrated PP rates during the main under-ice production period, from mid-May to September. Further, modeled 30-year (1980–2009) mean values and spatial patterns of sea ice concentration compared well with remote sensing data. Under-ice PP was higher in the Arctic shelf seas than in the Arctic Basin, but ratios of under-ice PP over total PP were spatially correlated with annual mean sea ice concentration, with higher ratios in higher ice concentration regions. Decreases in sea ice from 1980 to 2009 were correlated significantly with increases in total PP and decreases in the under-ice PP/total PP ratio for most of the Arctic, but nonsignificantly related to under-ice PP, especially in marginal ice zones. Total PP within the Arctic Circle increased at an annual rate of between 3.2 and 8.0 Tg C/yr from 1980 to 2009. This increase in total PP was due mainly to a PP increase in open water, including increases in both open water area and PP rate per unit area, and therefore much stronger than the changes in under-ice PP. All models suggested that, on a pan-Arctic scale, the fraction of under-ice PP declined with declining sea ice cover over the last three decades
Seabird pollutant dataset used for meta-analysis
No full textUnderlying dataset for the manuscript:Effects of maternal reproductive investment on sex-specific pollutant accumulation accumulation in seabirds: a meta-analysisAuthors: Daniel J Hitchcock, Tom Andersen, Øystein Varpe and Katrine Borgå.Accepted for publication in Environmental Science & Technology (2019).<br
Life history adaptations to seasonality
No full textThe thesis contains studies of animal life histories at high latitudes. Several topics are covered; from ecosystem consequences of life histories to tests of specific behavioural predictions put forward based on life history arguments. Work on complete life histories is also included in an attempt to understand the evolution of capital and income breeding in marine copepods. My main research questions, followed by main topics and findings, are as follows: • How are seasonal environments influencing life history traits and phenology? • What are the roles of storage as a reproductive adaptation? • How are individual states, particularly energy reserves, influencing optimal life histories and behaviour? Paper 1 deals with how growth of a high-latitude pelagic fish, the Norwegian spring-spawning herring, is scheduled during the annual cycle. Body mass data reveal a short period of rapid annual increase in body mass at the time when the copepod Calanus finmarchicus is the main prey. The food consumption (energy units) of the entire herring population is estimated, using a bioenergetics model, and compared with production estimates of C. finmarchicus. Large herring populations, particularly because of their selective predation on older stages, can influence population dynamics of C. finmarchicus, and may explain some of the copepod’s life history adaptations. Finally, estimates of spatial energy transport are presented; caused by herring migrating from oceanic feeding grounds to coastal overwintering and spawning sites. The large herring stock may be responsible for the world’s largest biomass transport caused by a migrating population. This flux of energy and nutrients is important for coastal species, and potentially for interactions not yet studied, such as between herring eggs and benthic invertebrates. Paper 2 is a short comment on recent studies of copepod life cycles that have suggested that the large lipid stores serve as a means of obtaining neutral buoyancy at a given depth - an ultimate explanation of energy stores. There is, however, a need to understand the use of energy reserves remaining after the winter, before we understand the ultimate explanation for storage. That is, we must study to what degree copepods are capital breeders (using energy reserves for egg production) as opposed to income breeders (relying on concurrent food intake for egg production). These ideas were pursued in papers 3 and 4 which are based on a life history model of the abundant Southern Ocean copepod Calanoides acutus. Life history tradeoffs arise in the model because bioenergetics, developmental constraints, and interactions with the environment (temperature, food availability and predation risk) are made explicit. Hence, trade offs need not be assumed. The model is statedependent and reproductive value of individuals with different developmental stage and condition is predicted by dynamic programming. The model predicts the optimal energy allocation and diapause strategies that maximise reproductive value at any time of the year, determining the entire life history strategy. A highly seasonal pattern in optimal egg-laying time is predicted. This optimality is, however, seen from an egg’s perspective. Actual egg production, as predicted from population simulations, do not match the seasonal peak in offspring fitness, which suggest that later life cycle stages are subject to trade-offs and constraints causing laying dates sub-optimal from the offspring’s perspective. Mechanism behind the mismatch are studied. Eggs from capital breeding have higher fitness than income bred eggs as capital breeding takes place early in the season, even before the phytoplankton bloom. The time an egg is produced influences its probability of: 1) reaching a stage capable of diapause; 2) developing large energy reserves, and; 3) developing to a stage capable of capital breeding next season. We conclude that seasonality in both growth potential and predation risk are key drivers of copepod life histories. Paper 5 is on the costs and benefits of capital breeding in aquatic environments, including ecosystem consequence that follow from capital breeding strategies such as the lipid transport of herring. Costs and benefits of carrying energy reserves are different for aquatic compared to terrestrial organisms. General analyses of the costs and benefits of capital breeding would improve by incorporating more of the findings from studies of marine organisms. Marine biologists, on the other hand, may better understand and appreciate the life history trade-offs of their study organism if theoretical concepts from the predominantly terrestrial literature were used more actively. Quantification of pre-breeding costs of a capital breeder strategy is one such issue. These costs may influence how we understand life cycle questions such as timing of diapause and other state-dependent decisions prior to breeding. Paper 6 is on a long lived seabird whose reproductive strategy includes sophisticated parental care. State-dependent behavioural responses are studied, and as in the papers above, an important state is body condition in terms of stored resources. The petrels are found to adjust chick feeding and guarding according to their own body condition, the body condition of their partner with whom they co-ordinate the chick-rearing period, and finally, adjustments in response to the chick’s needs for food and guarding. All these factors are found to play a role in determining individual behaviour. The results are obtained using a field experiment, and are discussed in relation to the life history strategies of seabirds
The role of the male common eider Somateria mollissima as a protector against nest-predation
No full textMale common eiders Somateria mollissima in high-Arctic colonies are known to remain with females during the first weeks of incubation; a behaviour not found in eider colonies further south. Other studies have observed that, whilst adult eiders in northern latitudes experience less predation, there can be much higher levels of predation on their nests and young. The objective of this study was to investigate why males at an eider colony in Svalbard were present for longer than elsewhere in their range, and whether this was related to protection from high predation levels. Through an observational study design, this study mapped population and predator dynamics within an eider colony near Longyearbyen, Svalbard. This study found that males were present for several weeks after the first females had started incubating, and once most males left the colony there was an increase in predation. Success of predators was higher at unattended nests; however overall success of predators was not found to be significantly lower if males were present in addition to females. If males were present at the nest, females were less likely to leave their nest to respond to gulls, allowing females to conserve energy and leave nests covered. The possibility that the tendency of males to remain with females for longer has emerged from asynchronous breeding or extra-pair mating is discussed, but the findings from this study indicate that it is a direct response to high levels of predation
The effect of seasonality on polar cod (Boreogadus saida) dietary habits and temporal feeding strategies in Svalbard waters
No full textClimate change in polar regions will likely disrupt the fine-tuned trophic interactions among organisms in Arctic marine ecosystems. Modifications in prey phenology and composition as well as increased competition and predation from boreal species expanding their range northward are expected to affect the key Arctic fish species polar cod (Boreogadus saida) and thus have important repercussions on the Arctic marine food web. Aside from climate, the extreme seasonal light variations at high latitudes are important for phenology and foraging. Endemic Arctic organisms such as polar cod may be adapted to these drastic light variations whereas, non-endemic species may be confronted with a new set of environmental variables that could limit their northward range expansion in the context of a warming Arctic climate. In order to assess the ability of polar cod to cope with future changes in marine Arctic ecosystems, it remains important to understand their dietary plasticity. The main goal of this study was to investigate the flexibility of polar cod feeding strategies across seasons by documenting its temporal position on the generalist-specialist spectrum. Polar cod were harvested on the western and northern coast of Svalbard in September, October, January, and May in fjords influenced by Arctic water masses and fjords influenced by Atlantic water masses. The organisms’ stomach contents were extracted and analysed and prey species were identified to the lowest taxonomic level possible. Specimens were expected to experience marked seasonal variability in their feeding success and foraging strategy. Polar cod feeding success was observed to be seasonally heterogenous, with winter specimens dispalying a higher probability of having empty stomachs compared to specimens from the fall or the spring. Seasonality affected polar cod diet in terms of ingested prey composition with fall specimen from Arctic domains feeding primarily on the hyperiid amphipod Themisto libellula. This suggests that larger demersal polar cod ascended in the water column in the fall to forage on this pelagic prey. The important contribution of fish prey throughout sites in the winter highlighted a flexible size-biased diet and the potential ability to switch diet to a temporarily abundant resource. Polar cod adopted a population specialist strategy in the fall and an individual specialist strategy in the winter. Therefore, the opportunistic feeding strategy adopted by polar cod is affected by seasonality insofar as diet is limited to a few preferred prey in the fall and diversified during the polar night likely as a results of visual constraints on selectivity of preferred prey
The nestling diet of Svalbard snow buntings identified by DNA metabarcoding
No full textTundra arthropods have considerable ecological importance as a food source for several bird species that are reproducing in the Arctic. The actual arthropod taxa comprising the chick diet are however rarely known, complicating assessments of ecological interactions. In this study, I identified the nestling diet of Svalbard snow bunting (Plectrophenax nivalis) for the first time. Faecal samples of snow bunting chicks were collected in Adventdalen, Svalbard in the breeding season 2018 and analysed via DNA metabarcoding. Simultaneously, the availability of prey arthropods was measured via pitfall trapping. The occurrence of 32 identified prey taxa in the nestling diet changed according to varying abundances and emergence patterns within the tundra arthropod community: Snow buntings provisioned their offspring mainly with the most abundant prey items which were in the early season different Chironomidae (Diptera) taxa and Scathophaga furcata (Diptera: Scathophagidae), followed by Spilogona dorsata (Diptera: Muscidae). An influence of breeding location on the diet could not be established, although tundra habitat explained significant differences in the trapped arthropod compositions. A selectivity analysis revealed a selection towards larger sized prey taxa, which could have implications for observed variations in snow bunting nestling success. This one year study shows the promising results of DNA metabarcoding as a non-invasive technique to assess diet variations and trophic interactions
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