English
norskBlar i forfatter "Varpe, Øystein"
Viser treff 21-30 av 30
-
Predator–prey interactions in the Arctic: DNA metabarcoding reveals that nestling diet of snow buntings reflects arthropod seasonality
(Journal article; Tidsskriftartikkel, 2023-07-06)Tundra arthropods are of considerable ecological importance as a seasonal food source for many arctic-breeding birds. Dietary composition and food preferences are rarely known, complicating assessments of ecological interactions in a changing environment. In our field study, we investigated the nestling diet of snow buntings (Plectrophenax nivalis (L., 1758)) breeding in Svalbard. We collected fecal ... -
Retention of ice-associated amphipods: possible consequences for an ice-free Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012-09-12)Recent studies predict that the Arctic Ocean will have ice-free summers within the next 30 years. This poses a significant challenge for the marine organisms associated with the Arctic sea ice, such as marine mammals and, not least, the iceassociated crustaceans generally considered to spend their entire life on the underside of the Arctic sea ice. Based upon unique samples collected within ... -
Seasonal pollutant levels in littoral high-Arctic amphipods in relation to food sources and terrestrial run-off
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-03)Increasing terrestrial run-off from melting glaciers and thawing permafrost to Arctic coastal areas is expected to facilitate re-mobilization of stored legacy persistent organic pollutants (POPs) and mercury (Hg), potentially increasing exposure to these contaminants for coastal benthic organisms. We quantified chlorinated POPs and Hg concentrations, lipid content and multiple dietary markers, in a ... -
Seasonal shifts in feeding patterns: Individual and population realized specialization in a high Arctic fish
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-21)Species with a broad and flexible diet may be at an advantage in a rapidly changing environment such as in today's Arctic ecosystems. Polar cod (<i>Boreogadus saida</i>), an abundant and ecologically important circumpolar Arctic fish, is often described as a zooplankton generalist feeder, which suggests that it may cope successfully with changes in prey composition. This description is justified ... -
Seasonal vertical strategies in a high-Arctic coastal zooplankton community
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-18)We studied the larger (>1000 µm) size fraction of zooplankton in an Arctic coastal water community in Billefjorden, Svalbard (78°40’ N), Norway, in order to describe seasonal vertical distributions of the dominant taxa in relation to environmental variability. Calanus spp. numerically dominated the herbivores; Aglantha digitale, Mertensia ovum, Beroë cucumis, and Parasagitta elegans were the ... -
A standard protocol for describing the evaluation of ecological models
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-21)Numerical models of ecological systems are increasingly used to address complex environmental and resource management questions. One challenge for scientists, managers, and stakeholders is to appraise how well suited these models are to answer questions of scientific or societal relevance, that is, to perform, communicate, or access transparent evaluations of ecological models. While there have been ... -
Temperature-dependent egg production and egg hatching rates of small egg-carrying and broadcast-spawning copepods Oithona similis, Microsetella norvegica and Microcalanus pusillus
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-07)Reproductive rates of copepods are temperature-dependent, but poorly known for small copepods at low temperatures, hindering the predictions of population dynamics and secondary production in high-latitude ecosystems. We investigated egg hatching rates, hatching success and egg production of the small copepods <i>Oithona similis</i> and <i>Microsetella norvegica</i> (sac spawners) and <i>Microcalanus ... -
Temperature-dependent egg production and egg hatching rates of small egg-carrying and broadcast-spawning copepods Oithona similis, Microsetella norvegica and Microcalanus pusillus
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-07)Reproductive rates of copepods are temperature-dependent, but poorly known for small copepods at low temperatures, hindering the predictions of population dynamics and secondary production in high-latitude ecosystems. We investigated egg hatching rates, hatching success and egg production of the small copepods <i>Oithona similis</i> and <i>Microsetella norvegica</i> (sac spawners) and <i>Microcalanus ... -
Two hundred years of zooplankton vertical migration research
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-04)Vertical migration is a geographically and taxonomically widespread behaviour among zooplankton that spans across diel and seasonal timescales. The shorter-term diel vertical migration (DVM) has a periodicity of up to 1 day and was first described by the French naturalist Georges Cuvier in 1817. In 1888, the German marine biologist Carl Chun described the longer-term seasonal vertical migration ... -
What we do in the dark: Prevalence of omnivorous feeding activity in Arctic zooplankton during polar night
(Journal article; Tidsskriftartikkel, 2023-07-04)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 ...
