The biogeochemical cycle of methane in the coastal zone and littoral of the Kandalaksha Bay of the White Sea

Microbiological and biogeochemical investigations of the processes of methane production (MP) and methane oxidation (MO) in the coastal waters and littoral of the Kandalaksha Bay of the White Sea were carried out. The studies were conducted in the coastal zones and in the water areas of the Kandalaksha Preserve, Moscow State University White Sea Biological Station, and the Zoological Institute (RAS) biological station in August 1999, 2000, and 2001 and in March 2001. The rate of CO2 assimilation in the shallow and littoral sediments was 35-27800 mug C/(dm(3) day) in summer and 32.8-88.9 mug C/(dm(3) day) in winter. The maximal rates of MP were observed in the littoral sediments in the zone of macrophyte decomposition, in local depressions, and in the estuary of a freshwater creek (up to 113 mul/(dm(3) day)). The maximal level of MO was observed in the shallow estuarine sediments (up to 2450 mul/(dm(3) day)). During the winter season, at the temperature of -0.5 to 0.5degreesC, the MP rate in the littoral sediments was 0.02-0.3 mul/(dm(3) day), while the MO rate was 0.06-0.7 mul(dm(3) day). The isotopic data obtained indicate that the C-org of the mats and of the upper sediment layers is enriched with the heavy C-13 isotope by 1-4parts per thousand as compared to the C-org of the suspension. A striking difference was found between the levels of methane emission by the typical littoral microlandscapes. In fine sediments, the average emission was 675 mul CH4/(m(2) day); in stormy discharge stretch sediments, it was 1670 mul CH4/(m(2) day); and under stones and in silted pits, 1370 mul CH4/(m(2) day). The calculation, performed with consideration of the microlandscape areas with a high production, allowed the CH4 production of 1 km(2) of the littoral to be estimated as 192-300 1 CH4/(km(2) day).