Zooplankton biomass and ETS activity during the Late Winter Bloom in the Canary Islands waters: Vertical migration and active flux

Abstract

Studies about carbon active flux due to diel migrants in the Canary Current are scarce. The wide range of physical structures such as upwelling zones, filaments, mesoscale eddies, and large oligotrophic areas makes this area unique. We measured zooplankton biomass and the electron transfer system (ETS) enzymatic activity as a proxy for zooplankton metabolism in areas of different productivities from the oligotrophic waters off La Palma Island (Canary Islands) to the upwelling zone off Northwest Africa during the late winter bloom. Biomass values and specific ETS activities varied between 355±136 and 695±186 mg prot m-2, and 10.6±2.6 and 26.3±3.2 μlO2 mg prot-1 h-1 in oligotrophic waters and productive areas, respectively. Migrant biomass was also measured by sampling during day and night using a WP-2 in the 0-200 m depth water column. Respiratory and total active flux (including respiration, mortality and excretion flux) were assessed using published empirical relationships. Values obtained in upwelling areas were 8.9 ±4.9 mgC m-2 d-1, while in oligotrophic waters were 6.4±1.1 mgC m-2 d-1. The results showed the importance of diel vertical migrations in the downward transport of carbon in the biological pump. As a first approach, we also measured 210Po activity concentration in zooplankton and water samples. Higher values were found in the large size fraction (>1000 μm organisms).