Denitrification in estuarine sediment stimulated by the irrigation activity of the amphipod Corophium volutator

Abstract

Sediment with different densities of Corophium volutator (Pallas), ranging from 0 to 19 800 ind. m-', were incubated in laboratory microcosms, and rates of oxygen uptake, denitnfication and nitrate ammonification were determined from sediment-water fluxes. The measured processes were stimulated differently by C. volutator; oxygen uptake, denitrification of NO, from nitnfication within the sediment, and denitrification of NOT from the overlying water were enhanced 2-, 3-and 5-fold respectively in the presence of 19 800 ind. m-?. This differential stimulation was explained by the different characteristics of diffusional solute transport at the sediment-water interface and mass transfer of water into the burrows where O 2 and NO? was depleted. Denitrification rates were calculated by using the lSN isotope pairing technique. The applicability of the ' 5 ~ isotope pairing technique for measunng coupled nitrification-denitrification in bioturbated sedlment was confirmed in a test incubation with different levels of 1 5 ~0 < added to microcosms with 12 000 C. volutatorind. m-'