Benthic oxygen flux in the highly productive subarctic Lake Myvatn, Iceland: In situ benthic flux chamber study

In situ paired light and dark-stirred benthic flux chambers were used to estimate dissolved oxygen flux across the sediment–water interface in Lake Mývatn, Iceland. Three sampling stations were selected, each station reflecting a specific sedimentary environment, benthic communities, and water depth. During this study the phytoplankton density was low. Spatial and seasonal variations of bottom DO concentration and DO flux have been observed during this study. The oxygen consumption rate at all study sites had a mean of –89 (±44) mmol m^–2 d^–1 while the oxygen production rate due to benthic algae had a mean of 131 (±103) mmol m^–2 d^–1. There was a strong correlation (r=0.91) between oxygen consumption rate and temperature. This was presumably because of the temperature influence on rates of microbial and macrobenthic processes. The mean benthic primary production rate at all study sites was 1216 (±957) mg C m^–2 d^–1 between June 2000 and February 2001. Annual gross benthic primary production was estimated from the gross mean daily benthic DO production (P) and Redfield's C:O₂ ratio of 106:138 to be 420 g C m^–2 y^–1 at station HO, 250 g C m^–2 y^–1 at B2 and 340 g C m^–2 y^–1 at station 95. Thus, the mean gross benthic primary production was estimated as 1151 mg C m^–2 d^–1 at station HO, 685 mg C m^–2 d^–1 at station B2, and 932 mg C m^–2 d^–1 at station 95.