The impact of the eastern oyster (Crassostrea virginica ) on growth and recruitment of the seagrass Halodule Wrightii

Interactions between seagrasses and benthic filter-feeders may have significant impacts on the extent of benthic primary production. I used field experiments to determine the effect of oyster density on the abundance and growth rate Halodule wrightii in Mississippi Sound, AL. Oysters were deployed at densities of 0, 15, 75, and 150 m-2 in 1 m-2 plots of H. wrightii in September 2004. Shoalgrass shoot density, growth rate, total suspended solids, porewater nutrients, light transmittance, and epiphyte loads were measured from October through December 2004, and June through July 2005. Results showed no significant relationship between oyster density and light transmittance, TSS, epiphyte loads, or seagrass recruitment. A significant positive relationship existed between oyster density and porewater NH4 and PO4. Growth rates were highest at intermediate densities of oysters, while high oyster densities negatively impacted growth rates, shoot densities, and plant biomass.