Where to Forage in the Absence of Sea Ice? Bathymetry As a Key Factor for an Arctic Seabird.
ABSTRACT: The earth is warming at an alarming rate, especially in the Arctic, where a marked decline in sea ice cover may have far-ranging consequences for endemic species. Little auks, endemic Arctic seabirds, are key bioindicators as they forage in the marginal ice zone and feed preferentially on lipid-rich Arctic copepods and ice-associated amphipods sensitive to the consequences of global warming. We tested how little auks cope with an ice-free foraging environment during the breeding season. To this end, we took advantage of natural variation in sea ice concentration along the east coast of Greenland. We compared foraging and diving behaviour, chick diet and growth and adult body condition between two years, in the presence versus nearby absence of sea ice in the vicinity of their breeding site. Moreover, we sampled zooplankton at sea when sea ice was absent to evaluate prey location and little auk dietary preferences. Little auks foraged in the same areas both years, irrespective of sea ice presence/concentration, and targeted the shelf break and the continental shelf. We confirmed that breeding little auks showed a clear preference for larger copepod species to feed their chick, but caught smaller copepods and nearly no ice-associated amphipod when sea ice was absent. Nevertheless, these dietary changes had no impact on chick growth and adult body condition. Our findings demonstrate the importance of bathymetry for profitable little auk foraging, whatever the sea-ice conditions. Our investigations, along with recent studies, also confirm more flexibility than previously predicted for this key species in a warming Arctic.
Project description:Here, we model current and future distribution of a foraging Arctic endemic species, the little auk (Alle alle), a small zooplanktivorous Arctic seabird. We characterized environmental conditions [sea depth, sea surface temperature (SST), marginal sea ice zone (MIZ)] at foraging positions of GPS-tracked individuals from three breeding colonies in Svalbard: one located at the southern rim of the Arctic zone (hereafter 'boreo-Arctic') and two in the high-Arctic zone on Spitsbergen ('high-Arctic'). The birds from one 'high-Arctic' colony, influenced by cold Arctic water, foraged in the shallow shelf zone near the colony. The birds from remaining colonies foraged in a wider range of depths, in a higher SST zone ('boreo-Arctic') or in the productive but distant MIZ (second 'high-Arctic' colony). Given this flexible foraging behaviour, little auks may be temporarily resilient to moderate climate changes. However, our fuzzy logic models of future distribution under scenarios of 1?°C and 2?°C SST increase predict losses of suitable foraging habitat for the majority of little auk colonies studied. Over longer time scales negative consequences of global warming are inevitable. The actual response of little auks to future environmental conditions will depend on the range of their plasticity and pace of ecosystem changes.
Project description:Ongoing global changes apply drastic environmental forcing onto Arctic marine ecosystems, particularly through ocean warming, sea-ice shrinkage and enhanced pollution. To test impacts on arctic marine ecological functioning, we used a 12-year integrative study of little auks (Alle alle), the most abundant seabird in the Atlantic Arctic. We monitored the foraging ecology, reproduction, survival and body condition of breeding birds, and we tested linkages between these biological variables and a set of environmental parameters including sea-ice concentration (SIC) and mercury contamination. Little auks showed substantial plasticity in response to SIC, with deeper and longer dives but less time spent underwater and more time flying when SIC decreased. Their diet also contained less lipid-rich ice-associated prey when SIC decreased. Further, in contrast to former studies conducted at the annual scale, little auk fitness proxies were impacted by environmental changes: Adult body condition and chick growth rate were negatively linked to SIC and mercury contamination. However, no trend was found for adult survival despite high inter-annual variability. Our results suggest that potential benefits of milder climatic conditions in East Greenland may be offset by increasing pollution in the Arctic. Overall, our study stresses the importance of long-term studies integrating ecology and ecotoxicology.
Project description:Delayed maturity, low fecundity, and high adult survival are traits typical for species with a long-life expectancy. For such species, even a small change in adult survival can strongly affect the population dynamics and viability. We examined the effects of both regional and local climatic variability on adult survival of the little auk, a long-lived and numerous Arctic seabird species. We conducted a mark-resighting study for a period of 8 years (2006-2013) simultaneously at three little auk breeding sites that are influenced by the West Spitsbergen Current, which is the main carrier of warm, Atlantic water into the Arctic. We found that the survival of adult little auks was negatively correlated with both the North Atlantic Oscillation (NAO) index and local summer sea surface temperature (SST), with a time lag of 2 and 1 year, respectively. The effects of NAO and SST were likely mediated through a change in food quality and/or availability: (1) reproduction, growth, and development of Arctic Calanus copepods, the main prey of little auks, are negatively influenced by a reduction in sea ice, reduced ice algal production, and an earlier but shorter lasting spring bloom, all of which result from an increased NAO; (2) a high sea surface temperature shortens the reproductive period of Arctic Calanus, decreasing the number of eggs produced. A synchronous variation in survival rates at the different colonies indicates that climatic forcing was similar throughout the study area. Our findings suggest that a predicted warmer climate in the Arctic will negatively affect the population dynamics of the little auk, a high Arctic avian predator.
Project description:Using GPS-tracked individuals, we compared foraging ecology and reproductive output of a High-Arctic zooplanktivorous seabird, the little auk Alle alle, between three years differing in environmental conditions (sea surface temperature). Despite contrasting environmental conditions, average foraging fights distance and duration were generally similar in all studied years. Also, in all years foraging locations visited by the little auk parents during short trips (ST, for chick provisioning) were significantly closer to the colony compared to those visited during long trips (LTs, mainly for adults' self-maintenance). Nevertheless, we also found some differences in the little auk foraging behaviour: duration of LTs was the longest in the coldest year suggesting more time for resting for adults compared to warmer years. Besides, birds foraged closer to the colony and in significantly colder water in the coldest year. Interestingly, these differences did not affect chick diet: in all the years, the energy content of food loads was similar, with the Arctic copepod, Calanus glacialis copepodite stage V being the most preferred prey item (>73% of items by number and >67% by energy content). Also chick survival was similar in all the study years. However, when examining chicks growth rate we found that their peak body mass was lower in warmer years suggesting that overall conditions in the two warm years were less favourable. While our results, demonstrate a great foraging flexibility by little auks, they also point out their vulnerability to changing environmental conditions.
Project description:Spring sea ice phenology regulates the timing of the two consecutive pulses of marine autotrophs that form the base of the Arctic marine food webs. This timing has been suggested to be the single most essential driver of secondary production and the efficiency with which biomass and energy are transferred to higher trophic levels. We investigated the chronological sequence of productivity pulses and its potential cascading impacts on the reproductive performance of the High Arctic seabird community from Svalbard, Norway. We provide evidence that interannual changes in the seasonal patterns of marine productivity may impact the breeding performance of little auks and Brünnich's guillemots. These results may be of particular interest given that current global warming trends in the Barents Sea region predict one of the highest rates of sea ice loss within the circumpolar Arctic. However, local- to regional-scale heterogeneity in sea ice melting phenology may add uncertainty to predictions of climate-driven environmental impacts on seabirds. Indeed, our fine-scale analysis reveals that the inshore Brünnich's guillemots are facing a slower advancement in the timing of ice melt compared to the offshore-foraging little auks. We provide a suitable framework for analyzing the effects of climate-driven sea ice disappearance on seabird fitness.
Project description:Climate models predict that by 2050 the Arctic Ocean will be sea ice free each summer. Removing this barrier between the Atlantic and the Pacific will modify a wide range of ecological processes, including bird migration. Using published information, we identified 29 arctic-breeding seabird species, which currently migrate in the North Atlantic and could shift to a transarctic migration towards the North Pacific. We also identified 24 arctic-breeding seabird species which may shift from a migratory strategy to high-arctic year-round residency. To illustrate the biogeographical consequences of such drastic migratory shifts, we performed an in-depth study of little auks (Alle alle), the most numerous artic seabird. Coupling species distribution models and climatic models, we assessed the adequacy of future wintering and breeding areas for transarctic migrants and high-arctic year-round residents. Further, we used a mechanistic bioenergetics model (Niche Mapper), to compare the energetic costs of current little auk migration in the North Atlantic with potential transarctic and high-arctic residency strategies. Surprisingly, our results indicate that transarctic little auk migration, from the North Atlantic towards the North Pacific, may only be half as costly, energetically, than high-arctic residency or migration to the North Atlantic. Our study illustrates how global warming may radically modify the biogeography of migratory species, and provides a general methodological framework linking migratory energetics and spatial ecology.
Project description:Since the first documentation of climate-warming induced declines in arctic sea-ice, predictions have been made regarding the expected negative consequences for endemic marine mammals. But, several decades later, little hard evidence exists regarding the responses of these animals to the ongoing environmental changes. Herein, we report the first empirical evidence of a dramatic shift in movement patterns and foraging behaviour of the arctic endemic ringed seal (Pusa hispida), before and after a major collapse in sea-ice in Svalbard, Norway. Among other changes to the ice-regime, this collapse shifted the summer position of the marginal ice zone from over the continental shelf, northward to the deep Arctic Ocean Basin. Following this change, which is thought to be a 'tipping point', subadult ringed seals swam greater distances, showed less area-restricted search behaviour, dived for longer periods, exhibited shorter surface intervals, rested less on sea-ice and did less diving directly beneath the ice during post-moulting foraging excursions. In combination, these behavioural changes suggest increased foraging effort and thus also likely increases in the energetic costs of finding food. Continued declines in sea-ice are likely to result in distributional changes, range reductions and population declines in this keystone arctic species.
Project description:Warming in the Arctic has been much faster than the rest of the world in both observations and model simulations, a phenomenon known as the Arctic amplification (AA) whose cause is still under debate. By analyzing data and model simulations, here we show that large AA occurs only from October to April and only over areas with significant sea-ice loss. AA largely disappears when Arctic sea ice is fixed or melts away. Periods with larger AA are associated with larger sea-ice loss, and models with bigger sea-ice loss produce larger AA. Increased outgoing longwave radiation and heat fluxes from the newly opened waters cause AA, whereas all other processes can only indirectly contribute to AA by melting sea-ice. We conclude that sea-ice loss is necessary for the existence of large AA and that models need to simulate Arctic sea ice realistically in order to correctly simulate Arctic warming under increasing CO2.
Project description:Ongoing and projected greenhouse warming clearly manifests itself in the Arctic regions, which warm faster than any other part of the world. One of the key features of amplified Arctic warming concerns Arctic winter warming (AWW), which exceeds summer warming by at least a factor of 4. Here we use observation-driven reanalyses and state-of-the-art climate models in a variety of standardised climate change simulations to show that AWW is strongly linked to winter sea ice retreat through the associated release of surplus ocean heat gained in summer through the ice-albedo feedback (~25%), and to infrared radiation feedbacks (~75%). Arctic summer warming is surprisingly modest, even after summer sea ice has completely disappeared. Quantifying the seasonally varying changes in Arctic temperature and sea ice and the associated feedbacks helps to more accurately quantify the likelihood of Arctic's climate changes, and to assess their impact on local ecosystems and socio-economic activities.
Project description:Eurasian continent has experienced cold winters over the past two decades in contrast with Arctic warming. Previous studies have suggested that the cold Eurasian winters are associated with Arctic sea-ice loss, while others attributed them to atmospheric internal variability. However, here we show that the Arctic and Eurasian climate linkage is driven by the combination between atmospheric teleconnection originating in the tropical oceans and Arctic sea ice. Like a battery charges a capacitor, El Niño heats the tropical Atlantic, and the warmer Atlantic condition persists until early winter of El Niño-decay year. We find that the persisting tropical Atlantic warming induces anomalous Rossby wave train arching to Eurasia, leading to Arctic sea-ice increase and Eurasian warming. In La Niña phase these changes are reversed. Our results therefore suggest that the combination of recent tropical Pacific cooling and Arctic sea-ice loss have contributed to the frequent Eurasian cold winters.