ORGANIC-MATTER MINERALIZATION IN INTERTIDAL SEDIMENTS ALONG AN ESTUARINE GRADIENT

A seasonal study of organic matter mineralization rates was made at 8 intertidal stations in the Westerschelde Estuary (The Netherlands). Or ganic matter mineralization rates, based on the gaseous emission of ca rbon dioxide and methane, showed significant dynamic temporal and spat ial variability at various scales. Annual rates of organic matter mine ralization varied from 8 to about 339 mol C m(-2) yr(-1). The temperat ure dependence of organic matter degradation was described using an Ar rhenius-type equation. Activation energies ranged from 54 to 125 kJ mo l(-1) and correlated negatively with depth-integrated rates of mineral ization. Spatial differences in mineralization were mainly due to diff erences in the lability of the organic matter, since the quantity of o rganic matter was similar between stations on an areal or volume basis . Average first-order decomposition rate constants ranged from 0.2 to 7 yr(-1) and decreased towards the seaward end of the estuary due to a geing of riverine-derived material, Intertidal sediments were estimate d to account for about 25% of the total carbon retention in the Wester schelde estuary.