Individual variation in seasonal movements and foraging strategies of a land-locked, ice-breeding pinniped

Marine mammal satellite telemetry studies can provide important tests of movement and foraging theory. Here we present the first satellite tracking study of Caspian seals (Pusa caspica), an endangered, ice-breeding phocid seal, endemic to the Caspian Sea. The Caspian Sea is one of the most variable habitats inhabited by any pinniped species, and lacks competing large piscivores. Under such conditions foraging theory predicts individual variation in foraging strategy may develop to reduce intra-species competition. We deployed 75 Argos satellite tags 2009-2012 on adult seals of both sexes, and used State Space Modelling to describe movement, and behavioural states. During winter in all years most individuals were mobile within the icepack, making repeated trips into open water outside the ice field, with only brief stationary periods that may be related to breeding activity. During summer 2011, 60% of tagged animals migrated into the mid and southern Caspian, while the remainder spent the ice free season in the north. Summer foraging locations were not restricted by proximity to haul out sites, with animals spending more than 6 months at sea. Maximum dive depths exceeded 200m, and maximum duration was greater than 20 minutes, but 80% of dives were shallower than 15m and shorter than 5 minutes. Hierarchical cluster analysis identified 3 distinct groups of summer dive behaviour, comprising shallow, intermediate and deep divers, which were also spatially exclusive, suggesting potential niche partitioning and individual specialisation on prey or habitat types. The results can contribute to assessment of impacts from anthropogenic activities and to designation of protected areas encompassing critical habitats

Inter-year variation in pup production of Caspian seals (Pusa caspica) 2005-2012 determined from aerial surveys

Assessing species abundance and reproductive output is crucial for evaluations of population dynamics, conservation status and the development of management objectives. The Caspian seal (Pusa caspica) is a key predator in the Caspian Sea ecosystem and is listed as “Endangered” by IUCN. Here we report on fixed-wing aerial strip transect surveys of the breeding population on the Caspian Sea winter ice field carried out in February 2005-2012. Potential detection biases were estimated by applying a Petersen mark-recapture estimator to the counts from double photographic observations. We also tested for effects of weather conditions on count results, and for correlations between pup production and ice conditions and net primary productivity (npp). Fluctuations in pup production estimates were observed among years, ranging from 8,200 pups (95% CI 7,130-9342) in 2010 to 34,000 (95% CI 31,275-36,814) in 2005. Total adults on the ice ranged from 14,500 in 2010 to 66,300 in 2012. We did not detect significant associations between pup production and either ice summary data (ice season length, and ice area) or npp. The observed inter-year variation may be partly due to underlying biological drivers influencing the fecundity of the population, although measurement errors arising from observation bias, plus variation in survey timing and weather conditions may also have contributed. Identifying the potential drivers of Caspian seal population dynamics will require extending both the survey time series and the quality of supporting data. However, inter-year fluctuations should still cause concern that the population may be vulnerable to environmental variability and ecosystem dynamics

Climate Change in the Baltic Sea Region: A Summary

Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge about the effects of global warming on past and future changes in climate of the Baltic Sea region is summarized and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focusses on the atmosphere, land, cryosphere, ocean, sediments and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in paleo-, historical and future regional climate research, we find that the main conclusions from earlier assessments remain still valid. However, new long-term, homogenous observational records, e.g. for Scandinavian glacier inventories, sea-level driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution and new scenario simulations with improved models, e.g. for glaciers, lake ice and marine food web, have become available. In many cases, uncertainties can now be better estimated than before, because more models can be included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth System have been studied and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication and climate change. New data sets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal time scales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first paleoclimate simulations regionalized for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA) and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics is dominated by tides, the Baltic Sea is characterized by brackish water, a perennial vertical stratification in the southern sub-basins and a seasonal sea ice cover in the northern sub-basins</p

Climate change in the Baltic Sea region: a summary

Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins

Climate change in the Baltic Sea:2021 fact sheet

Abstract Climate change effects on the Baltic Sea environment are manifold. It is for example expected that water temperature and sea level will rise, and sea ice cover will decrease. This will affect ecosystems and biota; for example, range shifts are expected for a number of marine species, benthic productivity will decrease, and breeding success of ringed seals will be reduced. The impacts will hence affect the overall ecosystem function and also extend to human uses of the sea; trawling will follow the fish towards southern areas, aquaculture will likely face a shift towards species diversification, and the value of most ecosystem services is expected to change — to name a few. This Climate Change Fact Sheet provides the latest scientific knowledge on how climate change is currently affecting the Baltic Sea and how it is expected to develop in the foreseeable future. It is aimed at guiding policy makers to take climate change into account, but also to the general public. Updated Baltic Sea Climate Change Fact Sheets are expected to be published approximately every seven years