Interannual changes in zooplankton on the West Spitsbergen Shelf in relation to hydrography and their consequences for the diet of planktivorous seabirds

Abstract

Kwasniewski, S., Gluchowska, M., Walkusz, W., Karnovsky, N. J., Jakubas, D., Wojczulanis-Jakubas, K., Harding, A. M. A., Goszczko, I., Cisek, M., Beszczynska-Möller, A., Walczowski, W., Weslawski, J. M., and Stempniewicz, L. 2012. Interannual changes in zooplankton on the West Spitsbergen Shelf in relation to hydrography and their consequences for the diet of planktivorous seabirds. – ICES Journal of Marine Science, 69: 890–901. The purpose of the work was to determine how atmospheric and oceanic processes (the North Atlantic Oscillation (NAO) and the Arctic Ocean Oscillation (AOO)) influence hydrography and zooplankton on the West Spitsbergen Shelf (WSS), and the impacts of the processes on chick meals of zooplanktivorous little auks Alle alle. There were distinct Atlantic and Arctic oceanographic domains on the shelf resulting from the presence of the West Spitsbergen Current and the Sørkapp Current, which contain different proportions of Calanus finmarchicus and C. glacialis. The abundance of warm- and cold-water species varied as a result of an interplay between processes in the atmosphere and ocean. In the Arctic domain, on which the study focused, the NAO impacted oceanography, zooplankton, and consequently little auk chick meals, with time-lags of 4–7 years. The diet of little auk chicks was more energy-rich when C. glacialis stage 5 in the Arctic community were more easily available. To date, the changes in zooplankton abundance on the WSS have not posed a threat to the ability of little auks to feed their chicks lipid-rich Arctic copepods.

Variability inCalanusspp. abundance on fine- to mesoscales in an Arctic fjord: implications for little auk feeding

“…Steen et al (2007) report consistently low numbers of Calanus glacialis AF in gular pouches, a stage that was not observed at all in net samples along a transect past the bird colony. A recent study covering a total of eight years (Kwasniewski et al 2012) showed the coupling for C. glacialis/C. finmarchicus ratio and, in support of earlier studies, they suggested that the foraging ground of the little auk is most likely limited to the Arctic water current, separated by a hydrographical front, from the Atlantic water current and not mixed water masses as in our study.…”

Parent-offspring interactions in a long-lived seabird, the Little Auk (Alle alle): begging and provisioning under simulated stress

“…Due to the evident linkage between body condition and survival (Harding et al 2011), adult birds should govern the degree of parental investment against the negative consequences on their own body condition. Exploring the mechanisms that regulate the parental investment might help to evaluate the trade-offs involved in the reproductive performance in Little Auks, which are particularly important in predicting their response to the worsening foraging conditions in the Arctic Kwasniewski et al 2012). …”

Large versus small zooplankton in relation to temperature in the Arctic shelf region

“…The net zooplankton catches described by Jakubas et al (2013) in the same area (Arctic-type waters, the Hornsund area) and at the same period as our study (the end of July) showed that C. glacialis represented 70% of the older life stages (CIV, CV and adults) of both mentioned Calanus species and that the fifth copepodite of C. glacialis constituted half of this amount. Moreover, multiyear observations conducted by Kwasniewski et al (2012) showed the substantial domination of C. glacialis older copepodite stages over C. finmarchicus in the Arctic shelf community at this time of the year.…”

“…This study provides only high-resolution LOPC measurements -information about zooplankton species composition is based on numerous previous studies conducted in the same study area (e.g., Kwasniewski et al 2010;Kwasniewski et al 2012;Jakubas et al 2013;Stempniewicz et al 2013;Trudnowska et al 2014;Trudnowska et al 2015;Trudnowska et al 2016). Using the abundance estimates and size structure data derived from the LOPC, we grouped plankton into two size fractions: a small size fraction (0.25-1.0 mm ESD), consisting of, e.g., Calanus nauplii, Oithona spp., Microcalanus spp., Pseudocalanus spp., and a large size fraction (1.0-2.5 mm ESD) -hereafter Calanus -represented predominantly by the older life stages (CIV, CV, adult) of Calanus spp.…”

“…The large frontal system situated along the WSS (Sakshaug et al 2009) is formed by two currents separated by a density gradient between the warm Atlantic Water of the West Spitsbergen Current and the cold Arctic water of the coastal Sørkapp Current (Saloranta & Svendsen 2001;Nilsen et al 2008;Kwasniewski et al 2010). While the total abundance of zooplankton is much higher in Atlantic waters, Arctic waters carry organisms of larger body size and with a higher lipid content, which results in their higher biomass and calorific value (Weslawski et al 1999;Kwasniewski et al 2010Kwasniewski et al , 2012. Copepods of the genus Calanus have extremely high calorific values (50-70% lipids of dry mass; Lee et al 2006;Falk-Petersen et al 2009) and are key species in the Arctic ecosystems (Stempniewicz 2001;Falk-Petersen et al 2002;Frandsen et al 2014), where they represent significant food items for planktivorous predators from the higher trophic levels, such as birds, fish and mammals (Falk-Petersen et al 1990).…”