Mass sedimentation of Phaeocystis pouchetii in the Barents Sea

Abstract

Mass sedimentation of gelatinous colonies of the prymensiophyte Phaeocystis pouchetii were observed in the upper 100 m of Atlantic water in the central Barents Sea. Sedimentation rates of particulate organic carbon and nitrogen as well as pigments were the highest recorded so far from oceanic environments of the North Atlantic or coastal areas of Norway. High relative concentrations of phytoplankton pigments found n the traps are interpreted as a combination of sinking of intact phytoplankton cells and undegraded pigments present in macrozooplankton faecal pellets. Evidence presented in this study implies that the zooplankton community of the Barents Sea was not able to control this phytoplankton spring bloom. The suspended and sedimenting organic matter was rich in carbon and pigments, but poor in nitrogen. This is explained by the presence of large amounts of carbon-rich mucilage which P. pouchetii colonies develop during their development. In addition to diatoms, sedimentation of a gelatinous phytoplankton species like P. pouchetii may contribute significantly to the formation of marine snow and vertical flux from the euphotic zone. However, degradation of P. pouchetii derived detritus at depths less than 100 m greatly diminishes the likely significance of P. puchetii blooms in processes such as the carbon flux to the deep ocean and sequestering of CO2.