Consequences of Atlantification on a Zooplanktivorous Arctic Seabird

Abstract

Global warming, combined with an increasing influence of Atlantic Waters in the European Arctic, are causing a so-called Atlantification of the Arctic. This phenomenon is affecting the plankton biomass and communities with potential consequences for the upper trophic levels. Using long-term data (2005-2020) from a high Arctic zooplanktivorous seabird, the little auk (Alle alle), we tested the hypothesis that the Atlantification affects its diet, body condition and demography. We based our study on data collected in three fjords in West Spitsbergen, Svalbard, characterized by distinct oceanographic conditions. In all three fjords, we found a positive relationship between the inflow of Atlantic Waters and the proportion of Atlantic prey, notably of the copepod Calanus finmarchicus, in the little auk chick diet. A high proportion of Atlantic prey was negatively associated with adult body mass (though the effect size was small) and with chick survival (only in one fjord where chick survival until 21 days was available). We also found a negative and marginally significant effect of the average proportion of Atlantic prey in the chick diet on chick growth rate (data were available for one fjord only). Our results suggest that there are fitness costs for the little auk associated with the Atlantification of West Spitsbergen fjords. These costs seem especially pronounced during the late phase of the chick rearing period, when the energetic needs of the chicks are the highest. Consequently, even if little auks can partly adapt their foraging behaviour to changing environmental conditions, they are negatively affected by the ongoing changes in the Arctic marine ecosystems. These results stress the importance of long-term monitoring data in the Arctic to improve our understanding of the ongoing Atlantification and highlight the relevance of using seabirds as indicators of environmental change.

Demographic responses of Arctic seabirds to spring sea-ice variations

“…In contrast, little auk survival may be affected by changes in spring sea-ice (assuming that the detected effect is not spurious). This would be coherent with previous results found in the same population suggesting that little auk survival was affected by summer environmental conditions (Hovinen et al, 2014;Descamps et al, 2022). Indeed, Hovinen et al (2014) suggested an effect of sea surface temperatures during the breeding season of the preceding year on little auk survival, even though the time-series used was relatively short (8 years) and the results mainly driven by 1 year with high SST values.…”

“…We did not detect any effect on Brünnich's guillemot survival or breeding success, but we found a positive effect of sea-ice with a lag of 2 years on the breeding success of little auks. In Svalbard, the little auk feeds mainly on large, energy-rich copepods (C. glacialis, stages CV; Descamps et al, 2022) whose life-history is affected by sea-ice (Ershova et al, 2021). Annual sea-ice concentration affects the abundance of early life stages of copepods (CI-CII) which are present in spring (May-June; Ershova et al, 2021).…”

“…For example, the availability of food resources in west Spitsbergen also depends on the advection of Atlantic water (Hop et al, 2019). Indeed, such Atlantic water inflow in west Spitsbergen fjords strongly affects both the amount and composition of the prey available to seabirds (e.g., Vihtakari et al, 2018;Descamps et al, 2022). Productivity in the fjords can also be affected by other processes like glacier discharge (Lydersen et al, 2014).…”

“…In the high Arctic, Brünnich guillemots and kittiwakes forage on ice-associated fish, such as polar cod Boreogadus saida (Mehlum and Gabrielsen, 1993;Vihtakari et al, 2018), and their population dynamics have already shown positive associations with sea-ice extent (Descamps and Ramírez, 2021). The little auk, the only exclusively zooplanktivorous seabird in the North Atlantic which feeds mainly on lipid-rich copepods Calanus glacialis (Lønne and Gabrielsen, 1992;Descamps et al, 2022), has also shown a strong association with sea-ice (e.g., Jakubas et al, 2012;Amélineau et al, 2019). However, we currently lack detailed information on the effects of sea-ice on demographic parameters, like survival and breeding success.…”

Drivers of change in Arctic fjord socio-ecological systems: Examples from the European Arctic

“…The borealisation of West Svalbard fjords, due to Atlantification, is already affecting seabirds via its impacts on zooplankton (Descamps et al, 2022).…”