Dissolved hydrogen and methane in Saanich Inlet, British Columbia

Abstract

Hydrogen, methane, and relevant microbiological and hydrographic observations were made to study the processes responsible for the observed distributions of the gases in Saanich Inlet, a seasonally anoxic fjord. Concentrations of surface waters were up to 22 (H 2) and 13 (CH 4) times atmospheric saturation. Below the surface hydrogen fell to undersaturation, rising to above saturation in the anoxic layer. Methane increased to a maximum at 30 m, and after a minimum at 125 m, increased greatly in the anoxic layer. Microbes cultured from inlet surface water produced hydrogen under experimental conditions, not by nitrogen fixation but while apparently denitrifying. Large numbers of protozoa present may provide anaerobic microniches for hydrogen and methane production, as might the intestinal tracts of the large populations of higher organisms in the inlet. Methane profiles in the upper 50 m are typical of waters outside the inlet, indicating regional sources and sinks. Hydrogen production and consumption rates, inferred to be rapid in the anoxic waters, nearly balance so that only slight increases in hydrogen occur there.