MONITORING PERFORMANCE OF SHALLOW, SUBTIDAL RESTORATION OYSTER REEFS USING ADVANCED TECHNOLOGIES: A CASE STUDY OF FELGATES CREEK REEF (YORK RIVER, VA)

Oyster reef habitats in Chesapeake Bay declined sharply in the last century, which stimulated substantial restoration efforts. To assess the effectiveness of reef restoration, reef performance has been monitored using a combination of habitat mapping and field sampling. Reef monitoring has been conducted effectively for deep and intertidal reefs, but shallow, subtidal reefs have not been mapped accurately due to logistical challenges. Here, we provide a protocol to sample shallow, subtidal restoration reefs accurately with high precision. Felgates Creek reef is a shallow (<3 m water depth), subtidal oyster reef constructed in 1999 in the York River, VA; the reef has not been mapped or sampled. The goals of this study were to: 1) map Felgates Creek reef and delineate sampling strata, 2) quantitatively assess reef performance by stratified random sampling, and 3) determine habitat suitability of Felgates Creek reef and surrounding habitat for restoration using a Habitat Suitability Index (HSI) for the York River.

A high-resolution Acoustic Doppler Current Profiler and RTK GPS base station were used to map the reef and define sampling strata by depth. Twelve random quadrat samples were collected, eight from the shallow depth stratum (A), 0.5-1.0 m water depth, and four samples from the deeper stratum (B), 1.0-1.5 m depth. A 0.25-m² quadrat was placed at each sampling point and all shell material within the plot was excavated. Each sample was cleaned and sorted, and live and dead oysters were measured (shell length) and photographed. Volume of each oyster, live and dead, was determined via volumetric displacement. Preliminary results indicate that oyster density was high (50.5 live oysters per m²) in the shallow stratum A, and rapidly declined to 1.0 live oysters per m² below stratum A. Multiple age classes were present in stratum A, which, when combined with the high density, indicate that the shallow portion of the reef has been stable over the past two decades. The assessment of HSI is in progress, with particular reference to the poor performance in stratum B. The advanced technologies utilized in this study allowed for assessment of restoration oyster reefs in all water depths, which can be used to guide monitoring of reef performance in restoration efforts.