A view that tidewater glacier fronts are important feeding grounds for marine predators is becoming widespread, although there is little direct evidence of their foraging activities and diet in these areas. Here, we conducted a spatial analysis of the stomach contents of ringed seals to investigate their diet and its relationship with glacier fronts, making the most of the unique opportunity provided by Inuit hunting, which allows obtaining stomachs with hunted locations. Our results showed that seals captured near glacier fronts consumed more prey than those captured farther away, particularly feeding on polar cod. Furthermore, the prey composition varied among capture locations, suggesting varied foraging strategies reflecting prey availability. Our study indicates that seals feed intensively at glacier fronts, emphasizing the potential for recent climate-induced glacier retreat to deprive seals of key foraging grounds, leading to changes in their behavior, diet, and habitat use.
Abstract Background Meiobenthic metazoans often showcase a puzzling combination of poor dispersal capabilities and wide geographical distributions. Because meiofauna ‘should’ be prone to endemism, the surprising observation of widely distributed morphospecies has spurred substantial interest and explanatory attempts. We place the searchlight on two small flatworm species – Itaspiella helgolandica and Notocaryoplana arctica – which are particularly restricted in habitat preferences and dispersal capabilities but which occur across the Arctic. Two hypotheses which could account for their wide distributions are explored: (1) populations are genetically divergent but showcase morphological stasis in an instance of cryptic speciation and (2) postglacial population expansion occurred recently enough that genetic drift and local adaptation has not produced divergent allopatric clades yet. Results We observed consistent gross and copulatory stylet morphology across local and global scales, confirming the general lack of morphological differences noted by other authors. Our phylogenetic analyses and species delimitation test (bPTP) of partial ribosomal gene sequences (28 S and 18 S rDNA) support the monophyly of each species, with no apparent signs of nascent allopatric lineage splitting. Likewise, haplotype networks do not indicate geography-derived clustering of populations but rather point toward interconnectivity across global and local scales. While our sample sizes and the genetic markers included limit the interpretations of the study, the star-like shapes of the haplotype networks together with negative Tajima’s D and significant, negative Fu’s Fs test values strongly point toward a history of recent population expansions in the studied flatworms. Conclusions We find strong support for postglacial population expansions as the most parsimonious explanation for the observed morphological similarities and a weakening of competing hypotheses, e.g. that of widespread cryptic speciation. We note that both species may still be dispersing over long distances e.g. through drifting of egg capsules, and our findings carry important implications for phylogeographical studies of meiobenthic invertebrates and the associated ‘meiofauna paradox’.
Climate change is playing a major role in the current global biodiversity crisis. However, despite climate change being most pronounced in the Arctic, its impacts on biodiversity in this region remains largely unknown. Here, we combined three decades of abundance data from various animal groups (from zooplankton to megafauna) and regions in the European Arctic and Greenland to assess recent changes in biodiversity within Arctic coastal communities. Our results support the "borealization" hypothesis in all regions and provide evidence that marine ecosystems in the North Atlantic Arctic are shifting toward a boreal (i.e. cold temperate) state. Arctic endemic species are generally declining in abundance, while boreal species are increasing. These changes in abundance are associated with an average increase in biodiversity (e.g. species richness), although there are important variations among animal groups. This increase might be transient and the long-term implications of the ongoing changes in Arctic coastal biodiversity on ecosystem functioning and services remain uncertain.
Abstract Mark-recapture analyses on the delineation of natural populations between areas often assume random sampling, with a between/within (B/W) area resighting ratio that declines towards zero as the population components of two areas become more-and-more isolated from one another, with fewer-and-fewer individuals mixing between areas. I use an individual based population model split in two areas to simulate this result, analysing also for the potential effects of the space-time fidelity of the mark-recapture sampling in the areas. I find that small B/W resighting ratios—that traditionally is taken as evidence of population isolation—can easily be observed within a completely mixing population if a random sampling scheme is restricted in space and/or time. Random sampling within restricted areas and time windows is not sufficient to estimate mixing rates and population isolation between areas, unless the resighting rates are analysed by a method that accounts both for the space-time fidelity of the scientific sampling scheme and the space-time fidelity of the distributional behaviour of the individuals in the population.
Despite their widespread presence across the North Atlantic, it remains unclear how long-finned pilot whales (Globicephala melas) differ regionally in their movement patterns and habitat use, and what this means for population structure. Satellite transmitters attached to pilot whales in the Faroe Islands (n = 11), East Greenland (n = 6), and Iceland (n = 2) between 2023 and 2025 revealed consistent regional differences in horizontal movements and habitat use. Whales tagged in the Faroe Islands displayed extensive offshore movements into deep oceanic waters more than 150 km from the coast. In contrast, whales tagged in East Greenland and Iceland mostly remained largely associated with shallower continental shelf waters and closer to the coast, with repeated use of the same shelf area across multiple years in East Greenland. Significant regional differences in displacement, bathymetry, and distance to coast indicate distinct oceanic and shelf-based movement strategies. These patterns are consistent with regional prey availability and distribution—shelf-associated whales exploit locally abundant species such as squid in East Greenland and possibly mackerel in Iceland, while whales undertaking long-distance oceanic movements target more widely distributed pelagic prey. Our results suggest ecological differentiation within a genetically homogenous North Atlantic population and emphasise the need to integrate movement ecology, genetics, and oceanography to better understand population structure and define meaningful management units in a rapidly changing subpolar ecosystem.
