Research: Oyster Restoration
The bottom of the Harbor was once covered with oyster reefs. Due to overfishing and pollution at the turn of the century, the eastern oyster (Crassostrea virginica) was virtually eradicated from the harbor. Today, water quality in New York Harbor has improved greatly, and oysters have begun to reappear after an absence of more than 100 years, but only in some places, and in low numbers. Functioning oyster reefs characterize the ecosystems where they exist; they support over 200 species of plants and animals, and filter particles out of large volumes of water. (A single oyster can filter three liters of water an hour.)
Improvements in water quality over the last century have allowed oysters to return to New York Harbor after an absence of 100 years. In the 1800s, oysters were the iconic food staple of lower Manhattan. They disappeared from New York Harbor around 1900 due to pollution, habitat destruction and over-fishing. Oysters are returning. They are not yet fit to eat, but their benefits far exceed their food value. They filter and clear water, so plants can grow, and they remove pollutants and toxins from the water. Oysters provide habitat for innumerable types of animals and countless microscopic organisms. As reefs, they protect shorelines against surge, current, tide and storm damage. The adjacent mud flat sustains a thriving benthic community. In this exhibit, the Reef and Flat live in unfiltered river water flowing through from beneath the exhibit, providing food for the filter-feeding oysters. The fishes and invertebrates in the exhibit are natural reef-dwelling animals, caught here in the neighborhood.
Over time, elements of the reef habitat and the animals of the reef ecosystem become more diverse and numerous, and their behavior more complex. Biodiversity, abundance and complexity are indicators of health and stability in an ecosystem. Fishes in the exhibit over the years have included sea bass, cunners, blackfish, toadfish, striped bass, gobies, sea horses, porgies, flatfish and searobins, as well as several species of mussels, crabs, and clams. Hydroids, bryozoans, sponges, anemones, worms and other Volunteer Settlers come in with the water as microscopic larvae, and then settle and grow in the exhibit.
Between Spring 2014 and Spring 2015, 205 oysters died while the remaining 317 oysters lived and grew. The mean size increased from 2.2cm to 3.02cm in that time.
This Reef was built and installed in 2013 by River Project and Harbor School staff and students with live oysters from Fishers Island Oyster Farm and The Urban Assembly New York Harbor School. Funding for the exhibit is from the National Science Foundation; New York State Department of Environmental Conservation Hudson River Estuary Program, and the Hudson River Improvement Fund of the Hudson River Foundation.
The River Project has studied wild and captive oysters at Pier 26 since 1998, and has begun to develop plans for creation of a small oyster reef in Tribeca. Growth studies show that small populations of wild oysters do live in the lower Hudson Estuary and that spat recruitment in the area of the proposed reef is present. Several years of oyster growth rate data on captive oysters suggest that oyster growth increases slightly at the sub-surface levels (below mean low tide). In the high turbidity environment of the lower Hudson, it appears that oysters grow more quickly in the upper photic zone, rather than at lower depths.
In addition, The River Project has a growing oyster outreach component in partnership with NY/NJ Baykeeper, the New York Harbor School, and the Harbor Estuary Stewardship Program. This work allows oyster gardeners to learn about local ecology while they participate in hands on restoration and promote a broader community support for improving the environmental health of the harbor. This program currently involves hundreds of oyster gardeners from schools and community organizations around New York City. For more information see Oyster Gardening.
The following short video, "Oysters - Not Just for Eating," on NPR's Science Friday features The River Project: