Methane production in Santa Barbara basin sediments

In vitro incubation of Santa Barbara Basin sediments indicated that methane production occurs at all depths sampled, including those in which sulfate reduction occurs. Methane production in the sulfate zone decreases with depth. U‐¹⁴C‐lactate is readily metabolized in the sulfate‐reducing zone, with ¹⁴CO₂ production being greater than ¹⁴CH₄ production. However, if sulfate is added to incubated sediments that have become depleted in sulfate, the ¹⁴CH₄ production increases dramatically at the expense of ¹⁴CO₂ production. Contrary to what has been observed in other ecosystems, sulfate stimulated methane production, especially from lactate. Experiments using 2‐¹⁴C‐acetate or H¹⁴CO₃ ^‐ have indicated that bicarbonate is the principal source of methane and acetate is oxidized to CO₂ in sediments from the methane‐producing zone.