Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate

Geophysical mapping and sampling data provide a record of changing environmental and faunal conditions within the Hudson River estuary during the mid- to late Holocene. On the shallow, broad marginal flats of the mesohaline Hudson, fossil oyster beds ( Crassostrea virginica) are found exposed on the river bottom and buried by sediment. The shallowest beds are well imaged in chirp sub-bottom and side-scan sonar data and form discrete flow-perpendicular bands, 0.6 - 1.0 km wide and up to 3 km long, which cover 30% of the river bottom. Radiocarbon-dated sediment cores indicate oysters thrived within two time periods from similar to 500 - 2,400 and similar to 5,600 - 6,100 cal. years B. P. Sediment and physical property data indicate a changing depositional regime consistent with the oyster chronology. Similar changes in oyster presence are found in local shell midden sites of the Lower Hudson Valley as well as elsewhere along the Atlantic coast, and may reflect climatic controls associated with warm - cool cycles during the Holocene. Oysters flourished during the mid- Holocene warm period, disappeared with the onset of cooler climate at 4,000 - 5,000 cal. years B. P., and returned during warmer conditions of the late Holocene. The most recent demise of oysters within the Hudson at 500 900 cal. years B. P. may have accompanied the Little Ice Age.