ESTIMATION OF THE MICROBIAL BIOMASS IN TIDAL FLAT SEDIMENT BY FUMIGATION-EXTRACTION

A transect of ten profiles was laid out in 20 m intervals on a tidal s and flat approximately 100 m from the east shore of Sylt until the nex t tideway was reached. Sediment samples were taken from 0-2 cm depth t oxic layer) and 2-4 cm depth (anoxic layer). The average content of or ganic carbon (C) was 2.41 mg g(-1) in the oxic layer and 1.86 mg g(-1) in the anoxic layer. The organic C content correlated positively with non-biomass C, 0.5 M K2SO4 extractable C, total nitrogen (N), cation exchange capacity (CEC), and the textural classes < 200 mu m, and nega tively correlated with the coarse sand fraction. The average total C:N ratio was 7.0 in the oxic layer and 6.7 in the anoxic layer, indicati ng that the C input comes entirely from the microflora. CHCl3-labile C was measured by the fumigation-extraction method and was converted to microbial biomass C (values in brackets). The average content of CHCl 3-labile C was 407 mu g g(-1) (903 mu g g(-)1) in the oxic layer and 2 14 mu g g(-1) (476 mu g g(-1)) in the anoxic layer. CHCl3-labile C did not correlate with CEC and the textural classes < 200 mu m, indicatin g that conditions other than the physical environment determine this f raction (C input, grazing).