Variability of microbial respiratory activity in relation to particulate organic matter over short time scales in a glacial Arctic fjord (Kongsfjorden, Svalbard)

Sinking biogenic particles drive respiration in the ocean interior, help to maintain the ocean's strong vertical gradient of inorganic carbon and related studies are important to determine the flow of organic matter along the water column. Sediment trap studies have shown that a low percentage of the surface primary production reaches the bottom. However, organic matter collected by sediment traps does not take into account the entire pool of oxidable organic matter, which includes the dissolved organic matter present in the seawater. The study of microbial respiration rates instead fills this gap, since respiration includes oxidation of both dissolved and particulate organic mater, providing an integrated estimate of the carbon utilization in the sea. In this context, a study on an Arctic fjord (Kongsfyorden, Svalbard) was done in late summer 2013, with the purpose of knowing the variability of microbial remineralization rates in relation to particulate organic matter over short time scales in a coastal station (water depth ~105 m), where a mooring (Mooring Dirigibile Italia, MDI: 78° 54 .859'N; 12° 15. 411' E) is positioned. A high variability of carbon dioxide production rates was recorded during the sampling days and this result was related to several factors. Useful information may be deducted for modelling studies of carbon flux in similar areas.