SURFACES OF HYDROTHERMAL VENT INVERTEBRATES - SITES OF ELEVATED MICROBIAL CH4 OXIDATION ACTIVITY

The high levels of CH4 emanating from deep-sea hydrothermal vents suggest that methane oxidation may be an important process in vent fields, especially in association with vent fauna. We measured the uptake of C-14-labeled methane by tissues and surfaces of common vent animals at a vent site in the northeastern Pacific. Low and variable levels of CH4 uptake were observed with limpet gills. However, the external surfaces of vent invertebrates, including gastropod shells and tube-worm tubes, were found to be extremely active sites of methanotrophic activity. Turnover times for CH4 based on (CH4)-C-14 oxidation rates averaged 1-2 d per individual limpet or vestimentiferan tube worm. These high rates provide the first evidence that methane oxidation can be a significant microbial process at a deep-sea hydrothermal vent site and adds external invertebrate surfaces as sites of elevated microbial activity in this environment. The methanotrophic bacteria on invertebrate surfaces can be readily grazed and may serve as a source of food for vent animals.