Do methane-producing zooplankton microflora explain elevated CH4 levels in marine environments?
Despite the highly oxygenated state of the surface ocean, supersaturation of methane a reduced volatile gas, can reach levels of up to 700% above background levels. Some sources for this methane have been described such as hydrocarbon seeps and anoxic slope sediments but these cannot explain the entire supersaturation. A biological process performed by methanogenic microbial communities, potentially inhabiting anaerobic environments within the guts of marine animals is thought to contribute to this flux. Two species of zooplankton, Euphausia pacifica and Cyphocaris challengeri, were investigated from Dabob Bay in Puget Sound, Washington. Samples were prepared for analysis of methane production in laboratory experiments and for examination of gut microflora. The production of small quantities of methane was observed in laboratory experiments (<0.1 ppm individual-1 day-1). One percent of the microbial population was identified as methanogens through microscopy. Bacterial 16S genes could
