Environmental drivers of spatial and temporal variation in infaunal communities at methane hydrates

Methane hydrates support unique infauna that varies from one hydrate area to another, therefore chemosynthetic environments could increase beta diversity in deep-sea environments. Our results show that oligochaetes, rather than dorvilleid polychaetes or Capitella spp. that characterize other cold seeps, dominate Barkley hydrates infauna off British Columbia (Canada). Most studies of faunal distribution of chemosynthetic environments focus on toxic effects of sulfur or limited oxygen, however, our study demonstrates that the contrasting food quality in hydrate patch mosaics also influences faunal distribution patterns. Food quality in the methane outcrop differs from adjacent sediments in a higher chl/phaeo ratio, lower lipid class diversity, high hydrocarbons (HC) and the presence of wax esters/steryl esters (WE/SE). Mean grain size, chl/phaeo ration, HC, WE/SE, triacylglycerides (TAG) and phospholipids (PL) appear primarily responsible for infaunal distribution patterns. The spatial extent of methane influence on food quality and community structure extends at least 20 m beyond the actual outcrop. The absence of temporal variation in infaunal community structure suggests a strong dependence on methane as a food source, even in relatively shallow hydrates (~900 m depth). Our data on environmental drivers of community structure, spatial extent, and temporal variation may prove valuable to managers interested in extraction of methane from hydrate sites as a potential source of energy.