Water-Quality Parameters and Total Aerobic Bacterial and Vibrionaceae Loads in Eastern Oysters (Crassostrea virginica) From Oyster-Gardening Sites

Oyster gardening is a practice designed to restore habitat for marine life and to improve water quality. This study determined physical and chemical water-quality parameters at two oyster gardening sites in the Delaware Inland Bays and compared them with total aerobic bacteria and Vibrionaceae concentrations in Eastern oysters (Crassostrea virginica). One site was located at the end of a man-made canal, whereas the other was located in an open bay. Measured water parameters included temperature, dissolved oxygen (DO), salinity, pH, total nitrogen, nitrate, nitrite, total phosphorus, and total suspended solids. The highest Vibrionaceae levels, as determined by the colony overlay procedure for peptidases, were at the canal site in September (3.5 × 105 g−1) and at the bay site in August (1.9 × 105 g−1). Vibrionaceae levels were significantly greater during the duration of the study at the canal site (P = 0.01). This study provides the first baseline levels for total Vibrionaceae in the Delaware Inland Bays. Minimum DO readings at the bay and canal sites were 3.0 and 2.3 mg l−1, respectively, far less than the state-targeted minimum threshold of 5.0 mg l−1. Total phosphorus levels exceeded recommendations of ≤0.1 mg l−1 at the bay and canal sites for all monthly samplings, with mean monthly highs at both sites ≥0.68 mg l−1 in August. Nitrogen occasionally exceeded the recommended level of 1.0 mg l−1 at both sites. Overall, waters were highly degraded from high phosphates, nitrogen, and total suspended solids as well as low DO.