MEPS 501:25-40 (2014)  -  DOI: https://doi.org/10.3354/meps10688

ABSTRACT: Arctic microphytobenthic in situ net community production (NCP) was measured via the oxygen exchange rate in benthic chambers equipped with optical sensor spots at 3 representative sandy sites in Kongsfjorden (Svalbard, 79° N, 12° E) at 3 to 11 m water depth during June 2008. No significant differences were detected between stations and depths in either photoautotrophic biomass or primary production. All sites showed low but variable rates of NCP, ranging from -0.3 to +0.6 mmol O₂ m^-2 h^-1 (-9 to +18 mg O₂ m^-2 h^-1). The numerical model of Walsby (1997) was applied to estimate seasonal and regional rates of nearshore NCP for 2008 using in situ P/E curve parameters, solar global radiation, wind data and satellite-derived sea surface temperatures. The highest daily NCP rates of 15 to 18 mmol O₂ m^-2 d^-1 were found throughout the Arctic spring and summer seasons (1 April until 31 August 2008) at shallow depths <15 m. The differences between modelled stratified and fully mixed water column conditions were small and in the range of 10%. Depth- and time-integrated NCP of the entire Kongsfjorden coastline during June 2008 yielded 9 t of O₂. A predicted increase in the sea surface temperature by 2°C would have only a marginal impact on the NCP (<3%). Our model sensitivity analysis of the uncertainties associated with P/E curve parameters and Q₁₀ values clearly showed a crucial dependence of NCP on the Q₁₀ values. Thus, further studies on temperature dependence are required.

KEY WORDS: Arctic benthic diatoms · Respiration and net production · Biomass · Sediment characteristics · Benthic chambers · Kongsfjorden