Vertical export of particulate organic carbon: Attenuation, composition and loss rates in the northern Barents Sea

The fate of primary production (PP) is closely linked to the ecosystem structure in aquatic environments. High pelagic consumption and recycling reduce quantity and quality of vertically exported organic material, while low to moderate pelagic consumption allows more carbon of higher quality to reach benthic communities. To evaluate the driving forces influencing changes in quantity and composition of vertical flux with depth and environmental conditions in ice-covered waters, short-term sediment trap deployments at 6-8 depths from 20 to 200 m were conducted. Eleven stations in the northern Barents Sea were investigated during early, peak and late bloom scenarios in 2003-2005. Vertical particulate organic carbon (POC) export ranged 140-760 mg C m ^-2 d ^-1 at 30 m and 58-720 mg C m ^-2 d ^-1 at 90 m depth. Strongest vertical carbon flux attenuation was observed during peak bloom scenarios. The pycnocline always defined the depth of the strongest attenuation. The POC export was highly correlated with Chl a flux ( r²=0.89) and with a low POC/Chl a ratio, this indicates that fresh material is being exported to depth. A tight coupling between POC export at 90 m and particulate PP ( r²=0.61) was observed and suggests that on an average 36% of daily PP was exported as POC. Deep vertical mixing observed in the Polar Front or less stable water masses did, however, enhance the vertical export and loss rates considerably. Annual estimates of vertical POC export to PP, suggests weaker retention, and thus stronger pelagic-benthic coupling in Arctic compared to the Atlantic region of the Barents Sea.