Rehoboth Bay, Indian River Bay, and Little Assawoman Bay are part of Delaware’s Inland Bay system. Rehoboth Bay spans thirteen square miles and is connected to the Indian River Bay in the south, the Lewes-Rehoboth Canal to the north, and other freshwater bodies. Eastern oyster (Crassostrea virginica) populations in the bays have decreased due to overharvesting and disease. Without eastern oysters, nutrient-rich water increases concentration and frequency of algal blooms that can result in areas in the bays that can cause a reduction in dissolved oxygen and lower the chance for marine wildlife to survive. However, eastern oysters’ ability to be natural filter feeders may help control nutrient levels and improve water quality, species diversity, and the productivity of fisheries.
The objectives of this project are to understand how artificial oyster reefs and oyster farms can affect water quality, species diversity, and oyster recruitment as well as understand the spawning timing of oyster larvae entering Rehoboth Bay. Two artificial oyster reefs, two oyster farms, and three control sites were chosen. Four oyster shell bags were deployed at every site. These bags are left in the bay for five weeks before being retrieved. Each site is also monitored by a YSI 556 Multiprobe to collect dissolved oxygen, temperature, pH, conductivity, ORP, and salinity data. Water samples are also collected and processed in the lab for total suspended solids, nitrate, nitrite, and orthophosphate as well as turbidity. Total Chlorophyll-a is monitored at each site using Turner Design Fluorometer. Next, oyster larvae will be retrieved through pump sampling and counted with ZooScan. Recent results from Dr. Ozbay’s lab show that artificial reefs have the most and oyster farms have the second highest species diversity, dissolved oxygen, and recruitment, and oyster farms had the highest turbidity due to high occurrences of waves and boat traffic to and around the farms. Literature also shows that eastern oysters begin spawning between mid-June and mid-September and our further efforts will target this timeline to obtain better data outcomes.
Keywords: Eastern oyster, recruitment, diversity, spawning, water quality
Acknowledgments: We acknowledge NOAA LMRCSC Grant #NA16SEC4810007, National Science Foundation EPSCoR Grant No. 1757353 and the State of Delaware, and Dr. Gulnihal Ozbay’s Environmental Health Laboratory Team.