Temperature Control on Temperate Lake Sediment Methane Production via Incubations

Freshwater ecosystems are a significant source of the powerful climate forcing gas, methane, to the atmosphere. Methane is produced in freshwater sediments through anaerobic respiration of organic matter. Temperature is a significant driver of methane production in lake sediments, but the exact sensitivity of production to temperature change is not fully constrained. Understanding the relationship between temperature and methane production rates is important as global lake temperatures continue to rise. We measured ex-situ lake sediment methane production rates from Harvey Lake in Northwood, NH (43°12'53.838"N 71°12'22.593"W). We collected the sediment in early June using a gravity corer. In addition, water samples were collected for analysis of chloride, pH, color, conductivity, turbidity, chlorophyll-a, total phosphorus, and dissolved organic carbon (DOC). Upon collection, the sediment cores were sectioned by depth (0-4cm, 8-12cm, 16-20cm) and kept at 4℃ until incubations were performed. Each incubation (4℃, 10℃, 16℃, 20℃, 25℃, 30℃) contained 3 replicates of 3g of sediment and ~20 mL of deionized water in 30ml glass vials for each depth segment. Methane concentrations in the headspace were measured with a gas chromatograph (GC-FID) daily across the incubation period (5-6 days). The relationship between methane production rates and temperature in lake sediments was determined and correlations between those rates, sediment depth, and water quality parameters were explored. These data have larger implications for a potentially changing methane cycle in temperate lake ecosystems, which contributes to global greenhouse gas concentrations and climate change.