25.2 Wednesday, Jan. 4 Benthic flow environments impacting larval recruitment on Crassostrea virginica oyster reefs REIDENBACH, M.A.*; WHITMAN, E.R.; Univ. of Virginia; Univ. of Virginia firstname.lastname@example.org
Restoration efforts to re-establish healthy Crassostrea virginica oyster populations along the Virginia, USA coast are focused on creating benthic habitat suitable for larval recruitment, survival and growth. To determine how benthic flow processes impact rates of larval recruitment, velocity and turbulence data was collected over multiple intertidal benthic surfaces including a mud bed, a healthy C. virginica oyster reef, and two restoration sites comprised of either C. virginica oyster shell or the relatively larger Busycom canliculatum whelk shell. Estimates of the drag coefficient, CD, used as a measure of hydrodynamic roughness, over a healthy reef were found to be 50% greater than those at restoration sites and four times greater than the mud bed. Enhanced fluid shear increased both Reynolds stresses and turbulent mixing above the reef, but within the interstitial areas between individual oysters, mean velocities and turbulent motions were reduced. Larval settling plates of varying triangular-shaped benthic roughness were used to mimic the natural topographic variability found along oyster reefs. The greatest larval recruitment occurred along interstitial regions between roughness elements, where shear stresses and drag forces, which act to dislodge settled larva, were found to be up to 10 times smaller than along exposed surfaces. Greater recruitment was also found on the more hydrodynamically rough B. canliculatum whelk shell as compared to the C. virginica shell restoration site. Results suggests that restoration efforts should consider creating 3D benthic topography similar to healthy oyster reefs when designing restoration habitat in order to provide hydrodynamic conditions and surfaces that promote larval recruitment, prevent burial by sediment, and provide refuge from predation.