INFLUENCES OF HISTORICAL LAND-USE CHANGE ON CHESAPEAKE BAY, RECONSTRUCTED FROM ENVIRONMENTALLY SENSITIVE BENTHIC OSTRACODES

Restoration of the Chesapeake Bay has become increasingly important to ensure the preservation and protection of its living resources. It is crucial to objectively quantify and understand which changes are caused by climate variability and which are anthropogenic.

A paleoecological study of the change in abundance of benthic ostracodes in Pocomoke Sound, southern Chesapeake Bay, has revealed a high-resolution water quality history. Preliminary data from two sediment cores reflect four distinct ostracode assemblages during the last 150 years from which water quality conditions can be inferred. The interval from 1850 to 1900 is marked by the dominance of Perissocytheridea brachyforma, suggesting an unusually wet interval with sustained low average salinity. The early 1900s experienced a drastic increase in the abundance of Actinocythereis captions and Loxoconcha sp., which generally inhabit polyhaline, well-oxygenated water. Around 1940, the abundance of Cytheromorpha curta increased sharply, signifying a decline in oxygen levels and/or increase in turbidity. After 1960, Megacythere repexa, another species tolerant of low oxygen, began a steady rise to dominance. These faunal patterns are similar to those found in other parts of the Bay suggesting near synchronous bay-wide changes in bottom conditions in response to land-use changes and water quality.