Differential response in chick survival to diet in least and crested auklets

The Arctic is undergoing widespread warming. In order to understand the impact of climate change on Arctic marine food webs, we studied the at-sea distribution of foraging little auks in contrasting conditions of the Greenland Sea. While the eastern side of the Greenland Sea has experienced recent warming, the western side is still dominated by cold, Arctic water in the East Greenland Current. We hypothesized that foraging little auks would be found in greatest abundance in cold Arctic waters bearing more lipid-rich prey, allowing them to deliver more energy-rich food to their chicks. To test our hypotheses, we made ship-borne bird observations and zooplankton tows, as well as analyses of chick meals at 2 little auk colonies adjacent to 3 distinct water masses in the Greenland Sea. Associated with the coldest water in the East Greenland Current, we found the highest concentrations of large Calanus copepods (C. glacialis and C. hyperboreus), as well as the highest concentrations of foraging little auks, indicating a relationship that is likely to be disrupted by increasing water temperatures. To assess potential future impacts of ocean warming, we used a coupled atmosphere-ocean global climate model (AOGCM) to predict Greenland Sea sea-surface temperatures over the study area at the end of the 21st century. Our results suggest that 4 of 8 little auk breeding colonies in the North Atlantic may be negatively impacted as temperatures exceed the thermal preferenda of large Calanus, which is the preferred prey of little auks during the breeding season.

Section: Impacts Of Present Oceanographic Changesmentioning

confidence: 99%

Foraging distributions of little auks Alle alle across the Greenland Sea: implications of present and future Arctic climate change

Karnovsky¹,

Harding²,

Walkusz³

et al. 2010

“…Field data on aspects of least auklet nesting success or the fitness of chicks at St. Paul I. are not available to evaluate the direct effects of shifts in diets. However, at St. Matthew I. in the central Bering Sea, least auklet chicks grew significantly faster when copepods (Calanus marshallae) were abundant in meals brought by adults (Springer et al 1986); there are strong relationships between least auklet demographic parameters and the amount of copepods in chick diets in the Aleutian Islands (Jones & Williams 2007); and at St. Lawrence I. in the northern Bering Sea, the daily survival rate of least auklet chicks was proportional to the amount of copepods in their diets (Gall et al 2006). Work on other species of seabirds has found strong negative correlations between stress and various demographic parameters ).…”

Section: Consequences Of Copepod Anomaliesmentioning

confidence: 99%

Hot oceanography: planktivorous seabirds reveal ecosystem responses to warming of the Bering Sea

Springer¹,

Byrd²,

Iverson³

2007

The Bering Sea has experienced dramatic warming in this century that has altered elements of the ecosystem, including the structure and productivity of the zooplankton community on the continental shelf, and the extent to which waters and associated plankton of oceanic origin have intruded onto the shelf. We documented temporal and spatial scales of these changes by monitoring diets of least auklets Aethia pusilla on the Pribilof Islands -least auklets are planktivores that specialize on the large calanoid copepods Neocalanus spp. from the basin and Calanus marshallae from the shelf. Diets were estimated in the summers of 1996 to 2006 by enumerating prey in regurgitated meals brought to chicks by adults, and by fatty acid analyses of live biopsy samples of adipose tissue from adult birds in 2003 and 2004, which provided additional insight. In the unusually warm 2000s, Neocalanus spp. apparently were excluded from regions of the outer shelf, where they typically occur in cooler years, and, concurrently, C. marshallae was depressed over a large region of the shelf because of chronic failures of spring cohorts to survive. Both changes were associated with anomalously high water temperatures over the middle shelf. The information provided by least auklets greatly improves our understanding of the consequences of environmental change and supplies clues about how communities and ecosystem processes respond to physical forcing. Continued warming of the magnitude seen in recent years could become a cause for concern for auklets and other planktivores in the eastern Bering Sea if it alters prey availability in ways detrimental to their populations.

“…High levels of nutritional stress reduce reproductive success and survival of adult seabirds, which might have immediate impact on population dynamics . Disappearance of lipid-rich oceanic cope pods from the diets can also impose severe nutritional limitations on growing auklet chicks (Springer et al 1986, Roby 1991, Gall et al 2006, which could increase their post-fledging mortality (Kitaysky et al 2003(Kitaysky et al , 2006. Thus, mediated by the physiological effects of nutritional stress, a warming climate is likely to have a negative impact on planktivores in the productive Green Belt area of the southeastern Bering Sea, as ob served in other areas of the North Pacific (Kitaysky & Golubova 2000, Sydeman et al 2006, Hipfner 2008, Bond et al 2011).…”

Section: Inter-annual Climate Variability Affects Temporal Dynamics Imentioning

confidence: 99%

Climate affects food availability to planktivorous least auklets Aethia pusilla through physical processes in the southeastern Bering Sea

Dorresteijn¹,

Kitaysky²,

Barger³

et al. 2012

Climate change might affect marine top predators by altering availability and nutritional quality of their prey. Climate effects vary on a regional basis, and our understanding of the relationships between fluctuations in climate and food resources in sub-arctic regions with seasonal ice cover is limited. We studied the effects of inter-annual climate variability (as reflected in the Pacific Decadal Oscillation, PDO, and the timing of the winter ice retreat) on zooplanktonplanktivorous predator linkages in one of the most productive regions of the southeastern Bering Sea, the 'Green Belt'. We examined changes in diets (species composition of chick meals and stable isotope signatures of adult blood) and relative food availability (as reflected in blood plasma concentrations of the stress hormone corticosterone) of planktivorous least auklets Aethia pusilla breeding on St. George I. We found that isotopic signatures of blood and composition of chick meals differed between the colonies. The proportion of energy-rich oceanic copepods Neocalanus spp. in the diet declined during warm years (high PDO and early ice retreat) on St. Paul but not on St. George. However, inter-annual and seasonal dynamics of corticosterone were similar between the colonies, and auklets experienced higher nutritional stress during warm compared to cold years. Our results suggest that the influx of prey-bearing water masses from the ocean basin and the retention time of oceanic copepods on the shelf are the main factors affecting composition of prey and its availability to auklets. We conclude that anticipated climate warming will negatively affect food availability of planktivorous predators in the Green Belt region of the southeastern Bering Sea.