MICROBIOLOGICAL STUDY ON THE METHANE PRODUCTION IN MARINE

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Membrane lipids of methanogenic bacteria are composed of special ether-linked glycerelipids, different from most of bacteria. So it is possible to estimate biomass of marine methanogenic bacteria and their activity by determining the lipid components in marine sediments. In the coastal eutrophicated sediments, such as Tokyo Bay, Aburatsubo Inlet and inner most part of Suruga Bay, methane concentrations were observed 0.12-93 nmol/g in the interstitial water samples, and lipid concentrations were 17-152 ng/g. These values were closely related in each sediment. Incubation experiments with these sediment samples showed that there are several groups of methanogenic bacteria in the sediments, such as utilizers of acetate, hydrogen+carbon dixide gasses, and methanol. Their activities were much higher than the mrethanogens obtained from off shore sediments. In the sediments of off shore waters like Sagami and Suruga Bays, methane concentrations were 0.32-0.65 nmol/g in the interstitial waters, and lipid concentrations were 4.6-21 ng/g. It was observed in the incubation experiments that methanol utilizers were much lower compared with eutrophicated sediments. Methanogenic activities of the intestinal micro flora of common zooplankton like copepods and euphausia were studies. Methanogenic activities were observed to be 1.8 micro mole per fecal pellets of 30 specimens of euphausia. In another experiment 615micro mols/g of methane were produced during 60 days of incubation. The microflora were observed to be methanol utilizers.