The effect of a strong warm winter on subtropical zooplankton biomass and metabolism

Abstract

Winter 2010 was the warmest of the last 30 years in the subtropical oceanic waters north of the Canary Islands. Sea surface temperature was always above 19?C, p romoting a strong stratification and preventing the expected late winter bloom. The knowledge of how planktonic organisms respond to such a warm scenario is of paramount importance to predict the effect of future ocean changes. In this study, zooplankton biomass and gut fluorescence (GF), electron transport system (ETS) activity, and aminoacyl-tRNA synthetases (AARS) activity were measured as proxies of metabolism in the oceanicwaters north of the Canary Islands during the winter-spring period of 2010. Mesozooplankton biomass, GF, and ETS activity showed lower values compared with previous studies in the area under normal winter conditions. However, relatively higher than expected mesozooplankton biomass was observed during the normal postbloom period in these waters, and AARS activities were relatively high throughout the period studied. This apparent paradox could be tentatively explained by the observed inputs of dust deposition from the Sahara desert. Our findings show how warming and dust events may interact, affecting the zooplankton biomass and metabolism in these subtropical waters.