Resuspension and its effects on organic carbon recycling and nutrient exchange in coastal sediments: in situ measurements using new experimental technology

The effect of resuspension on sediment-water solute exchange was studied in the archipelago outside the city of Goteborg (Sweden) during the winter months 2001/2002 by a combination of benthic flux (employing both in situ and laboratory incubations), meteorological and hydrodynamic measurements. Resuspension was created in in situ incubation chambers to study the possible resuspension effect on the fluxes of nutrients, oxygen and total carbonate. In most cases, resuspension changed the flux rates. The fluxes of oxygen, total carbonate and phosphate decreased during the resuspension event. The oxygen fluxes before resuspension were between 15 and 23 mmol m(-2) day(-1) in the four chambers, and decreased during resuspension to between 8 and 18 mmol m(-2) day(-1). The fluxes of total carbonate in the chambers before resuspension were 12-35 mmol m(-2) day(-1) and decreased to 4 - 15 mmol m(-2) day(-1). The change for each flux during resuspension was statistically significant. The fluxes of nitrate-nitrite and silicic acid increased, whereas the fluxes of ammonium did not change significantly. Hydrodynamic and meteorological data showed that the natural created resuspension at the study site were not due to wind-induced waves, but to strong bottom currents that can be caused when water built-up against land during strong wind events. When the wind abates, the water is flushing back and creates strong currents high enough to cause resuspension of the bottom sediments. A major storm passing the area during the experimental period caused particulate material to suspend to a concentration of about 11 mg/l in the bottom water, which was similar to the suspended material concentration in one set of the incubation chambers. (C) 2002 Elsevier Science B.V. All rights reserved.