Zooplankton-mediated carbon export: A seasonal study in a northern Norwegian fjord

Abstract

In a northern Norwegian fjord throughout the productive season, sediment traps were consecutively deployed at four depths from March until October in order to study the role of zooplankton on vertical export of organic matter. The field campaign included 26 cruises to a permanent station located in the basin of Balsfjord (180 m), with the most intensive sampling conducted during spring. The zooplankton community greatly influenced the vertical flux of particulate organic carbon (POC) through production and sinking of faecal pellets (FP). Faecal pellets explained ~40% of the POC flux leaving the upper 100 m during the productive season (corresponding to ~10 g C m−2). The average monthly faecal pellet carbon (FPC) contribution ranged widely between 7 and 75% of POC. Euphausiids were the single most important contributor to the vertical FP flux and made up >90% of the FPC during certain periods. Faecal pellets produced by small and medium-sized copepods, although found in high abundance, played a minor role for the vertical flux, suggesting significant retention processes in the upper layers.