Wednesday, All Day in Poster Hall
, Thursday, All Day in Poster Hall
(subject to change)
Benthic invertebrates play an important role in biogeochemical cycling in estuarine sediments. These same organisms also tend to disappear with the onset of the persistent hypoxia associated with eutrophication. In a series of laboratory experiments conducted using organisms and sediments from a shallow estuary currently undergoing rapid eutrophication, we investigated how common macrofauna influence sediment-water column fluxes of oxygen and nutrients both directly by changing the sediment redox status and indirectly by controlling microalgal production. The polychaete Nereis virens had the strongest positive influence on sediment oxygen demand, increasing overall fluxes by ventilating burrows and promoting the surface penetration of oxygen measured using microelectrodes. The grazing snail Ilyanassa obsoleta decreased microalgal production significantly which led to a concomitant increase in the release of ammonium and phosphate from the sediments. The hard clam Mercenaria mercenaria also decreased microalgal production, but there was a less obvious impact on sediment nutrient release. Overall, we found significant negative relationships between microalgal production and ammonium and silica fluxes, and positive relationships between ammonium, phosphate and silica release. Our results suggest that the composition of the macrofaunal community significantly impacts sediment nutrient release and oxygen demand and is an important determinant of water column nutrient availability.
