Methanogenic activity in plankton samples and fish intestines A mechanism for in situ methanogenesis in oceanic surface waters

When plankton samples were incubated anaerobically with a cysteine-sulfide reducing agent, pronounced methane evolution occurred. This activity was inhibited by air, CHCl₃, C₂H₂, and 2-bromoethanesulfonic acid. Adding [¹⁴C]CO₃²⁻ resulted in accumulation of [¹⁴C]CH₄. Portions of the digestive tracts of three fishes were incubated in methanogenic media, and two of the samples showed the presence of methanogenic bacteria.