Seasonal fluxes of phosphate and ammonium across the sediment-water interface in a shallow small estuary (Palmones River, southern Spain)

Abstract

Seasonal vanations in oxygen, phosphate and arnmonium fluxes between the sediment and overlying water were measured in a small shaiiow estuary (Palmones River Estuary, southern Spain) from Juiy 1996 to Juiy 1997. Fluxes at the sediment-water interface were measured in situ and compared with those obtained from the Pore water gradients. Oxygen consurnption rates ranged from 62.5 to 87.4 mmol m-' d-', and were highly correlated with phosphate (226 to 1597 pmol m-' d-') and ammonium (3189 to 9561 pmol m-' d-') fluxes. The diffusive fluxes of phosphate and ammonium, computed from the Pore water gradient, were lower than those measured in situ (from 7 to 24 tirnes for phosphate and from 21 to 55 tirnes for ammonium). Nutnent fluxes are weii correlated with temperature and with the C:N ratio of organic matter within the upper 2 cm of the sediment.