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Methane emission from the coastal area in the Southern Baltic Sea

: Heyer, J.; Berger, U.


Estuarine, coastal and shelf science 51 (2000), Nr.1, S.13-30
ISSN: 0272-7714
Fraunhofer IFU; 2002 in Helmholtz-Gesellschaft integriert
methane; emission; methanogenesis; sediment; automatic measurement; floating chamber; brackish water ecosystem; Baltic Sea

In the shallow coastal area of the brackish water ecosystem of the Baltic Sea, between the Islands of Rügen and Hiddensee (Southern Baltic, Germany), methane emission was continuously determined with floating measuring chambers and automatic sampling equipment. Data were collected during six measuring periods in two years (1995, 1996).The evaluation of more than 5700 measuring series demonstrated very strong seasonal and interannual variations of methane emission, with extremely high rates in the range between 24 and 104 mg CH4 m high -2 h high -1 in June/July 1995, and the lowest values in the range between 0.03 and 0.11 mg CH4 m high -2 h high -1 in October 1996. The highest single emission rate was 243 mg CH4 m high -2 h high -1. Therefore this shore region represents, at least periodically, a hot spot for methane emission from a brackish water ecosystem into the atmosphere. The crucial controlling factor for the interannual and seasonal variations of methane emission and also for the small spatial differences was found to be the amount of organic matter in the sediment. This exerted a direct influence on methanogenesis and additionally indirect effects on oxygen dynamics and the relationships between methanogenesis and sulphate reduction. The significant correlation between methane emission and temperature in the water and sediment demonstrated that diurnal and long-term variations of emission rates during each season were mainly regulated by temperature. Only at low emission rates did other, indirect ecological factors become more important in controlling methane emission.