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Total benthic oxygen uptake in two Arctic fjords (Spitsbergen) with different hydrological regimes

Kotwicki L., Grzelak K., Opaliński K., Węsławski J. M.

Oceanologia

2018

No. 60 (2)

107--113

Benthic total oxygen uptake (TOU) was measured in two Arctic fjords (NW Spitsbergen shelf) with different hydrological regimes: Hornsund with “cold” coastal Arctic waters and Kongsfjorden with “warm” Atlantic shelf waters. TOU rates in Kongsfjorden were more than 50% higher than in Hornsund. This is presumably related to the relatively higher biomass of bacterial and faunal (meiobenthos and macrofauna) communities in Kongsfjorden as compared to Hornsund caused by the source of organic matter: Kongsfjorden is dominated by marine, Hornsund by terrigenous organic matter. We conclude that the quality of organic matter supplied to marine sediments influences the biomass of benthic organisms and the rate of oxygen consumption. Therefore the Kongsfjorden sea bed has much higher oxygen uptake and hence a greater carbon demand than Hornsund.

Importance of bacteria and protozooplankton for faecal pellet degradation

Morata N., Seuthe L.

Oceanologia

2014

No. 56 (3)

565--581

The degradation mechanisms of faecal pellets are still poorly understood, although they determine their contribution to vertical fluxes of carbon. The aim of this study was to attempt to understand the microbial (bacteria and protozooplankton) degradation of faecal pellets by measuring the faecal pellet carbon-specific degradation rate (FP-CSD) as an indicator of pellet degradation. "In situ" and "culture" pellets (provided by the grazing of copepods in in situ water and in a culture of Rhodomonas sp. respectively) were incubated in seawater from the chlorophyll a maximum and 90 m depth, and in filtered seawater. When microbes were abundant (at the chlorophyll a maximum), they significantly increased FP-CSD. In addition, culture pellets had a higher FP-CSD than in situ pellets, suggesting that the results obtained with culture pellets should be treated with caution when trying to extrapolate to natural field conditions.