Methane sources, sinks and fluxes in a temperate tidal Lagoon : the Arcachon lagoon (SW France)

The Arcachon lagoon is a 156 km(2) temperate mesotidal lagoon dominated by tidal flats (66% of the surface area). The methane (CH4) sources, sinks and fluxes were estimated from water and pore water concentrations, from chamber flux measurements at the sediment air (low tide), sediment-water and water-air (high tide) interfaces, and from potential oxidation and production rate measurements in sediments. CH4 concentrations in waters were maximal (500-1000 nmol l(-1)) in river waters and in tidal creeks at low tide, and minimal in the lagoon at high tide (