Silicic acid regeneration from estuarine sediment cores*

The release of silicic acid from sediments is known to play a n important role in determining the silicic acid concentration in the water columns of estuaries, but factors controlling the rate of release are poorly understood. Silicic acid efflux from sandy Chesapeake Bay sediment cores that were maintained in the dark was strongly dependent on biogenic silica deposition, temperature and salinity, but was independent of oxygen concentration in the overlying water. Silica dissolution and release from the cores accelerated rapidly with temperature above 15 "C. The release rate also accelerated very rapidly with salinity increase between 10 O/m and 20 %, but was less dependent on change in salinity in the low and high ranges. These findings help account for observed late summer maxima in water-column silicic acid concentrations in mesohaline regions of Chesapeake Bay.