Respiration and biochemical composition of sedimenting organic matter during summer in the Barents Sea

--Sedimentation of particulate carbon and nitrogen, pigments (fluorometric and HPLC analysis) as well as the activity of the respiratory electron transport system in sedimented matter were studied with unpoisoned, short-term deployed sediment traps during June in the central Barents Sea. The vertical flux of sedimenting material and its biochemical composition in the central Barents Sea was different during summer compared to spring with decreased flux of organic matter and decreased relative supplies of particulate nitrogen, but increased phaeopigment concentrations. The summer situation in the Barents Sea is characterized by recycling of the bulk of the suspended matter in the upper layers, a comparatively small loss of suspended biomass, but high sinking rates of some few, large particles, presumed to be faecal pellets. Respiration calculated as a daily loss rate of carbon in the sedimented material was on average only 1.4% day1. Loss was strongly temperature dependent. At in situ temperatures >5°C, it is necessary to estimate turnover rates for sedimenting carbon in non-poisoned traps for an accurate elemental budget of a system and for interpretation of estimates from long-term trap deployments.