Seasonal variation of mesozooplankton biomass, abundance and copepod grazing in the central Cantabrian Sea (southern Bay of Biscay)

Abstract

Size fractionated mesozooplankton biomass, abundance and copepod grazing were investigated over an annual cycle (1998) at two stations off Cudillero (central Cantabrian Sea). Mesozooplankton biomass was higher in summer/early autumn, reaching ∼3000 mg dw m-2 in September. Copepods were the most abundant taxonomic group, representing 91 and 81% of the total mesozooplankton abundance in the coastal and shelf-break station respectively. Copepod gut contents were higher in summer at the coastal station, while the shelf-break station showed maximum gut contents in April. Gut contents were linearly related to integrated chlorophyll, except in the case of large animals at the shelf break station. Copepod community carbon ingestion was higher from June to September at both stations, reaching a maximum value of ∼165 mg C m-2 day-1. Calculated grazing rates translates into an average daily consumption values of 8.7% (coast) and 5.25% (shelf-break) of total chlorophyll stock, or 20% (shelf-break) of total primary production.