| Abstract |
The modern organic carbon flux of the Sanaga River and the rivers around the Bay of Douala is estimated to be 0.62-0.79 x 10(6) t yr(-1). In reality, mean Holocene sedimentation of organic carbon, including a presumed low biological production in the euphotic zone, is only 41-52 % of this-value. Substantial biodegradation in the salty and brackish turbid waters in the estuaries affects the POC and DOC arid corresponds to the highest bacterial densities. Between salinity 6 and 21, the data indicate a non-conservative behaviour of the suspended: and dissolved organic matter (POC and DOG). A breakdown of nearly 50 % of organic carbon is observed both in suspended matter of the open sea and in marine muds of near equal grain-size distribution. Incubation experiments show in the first few days the relative stability of POC in fresh water suspensions, where only the DOC is susceptible to degradation, In the fresh water-salt water mixing zones, where there are no autotrophic or heterotrophic developments, experiments indicate a 25-65 % loss of POC + DOC. after 96 h. In the clear salt water of the open sea, biodegradation is very low, though DOC becomes more and; more concentrated during transport. Off Campo, on the southern boundary of the Cameroonian shelf, a phytoplanktonic bloom was; encountered with a spectacular biodegradation of 45 to 65 % occurring after 24 h. Such quantitative approaches applied to long-term (10(4) years) processes imply that the present state can be regarded as a representative for the whole Holocene climatic conditions. |
