Eastern Oyster (Crassostrea virginica) Filtration Efficiency of Chlorophyll-a under Dynamic Conditions in the Hudson-Raritan Estuary at Pier 40, New York City

Eastern oyster (Crassostrea virginica) abundance has declined severely over the past century along the Atlantic and Gulf coasts of the United States. For varied reasons, overfishing among the foremost, bivalves no longer make up considerable reefs as was common. While discourse continues on oyster restoration and augmentation, gaps in knowledge of C. virginica and regional environmental interactions remain. Our primary aim was to examine the C. virginica filter feeding of phytoplankton in the Hudson River Estuary, New York City. Secondarily, this study examined the filtration of these oysters in relation to environmental attributes. Chlorophyll-a, the predominant photosynthesizing pigment in red and green algae, is an indicator of phytoplankton productivity in aquatic settings. Crassostrea virginica consumes first-tier plankton from the water column’s seston; thus analysis of chlorophyll-a content allows estimating phytoplankton concentrations, from which oyster filtration efficiency (FE) was quantified. Water conditions (temperature, dissolved oxygen, pH, salinity, turbidity, tide and flow rate) also were recorded. Spectrophotometric determination of chlorophyll-a concentration methodology was derived from the Standard Methods text favored by the US EPA. This project compared real-time Hudson River Estuary (HRE) water samples prior to passing through a contained oyster reef and samples of water post-filtration. This sampling scenario was unique as the contained reef used was fed by HRE water. Most studies on oyster filtration have been laboratory-based, and few assessed oysters in the field. This study took place at Pier 40, the River Project Wetlab, lower Hudson River along Manhattan. The FE of this reef was calculated for two months during various environmental states which can be the basis of future investigations. Statistically significant differences were found between pre- and post-filtration water samples (Z = 4.620, p < 0.001). This study provides a glimpse at how the oysters fare in the HRE environment and expands upon known oyster ecological services and environmental interactions.