From the time of its discovery in the Gulf of Mexico in the 1940′s until about 1990, a single-celled marine parasite (Perkinsus marinus) was rarely spotted north of the Chesapeake Bay. Perkinsus marinus is best known for causing large-scale die-offs of the commercially important Eastern Oyster (Crassostrea virginica). Since 1992, however, outbreaks of the parasite have been occurring as far as 310 miles north of the Bay. The winter water temperature off of the East Coast is an important predictor of the parasite’s success. If the winter water temperature falls below 37.4 degrees Fahrenheit, the parasite does not reproduce as readily and its numbers become limited. Since the 1960s, this temperature has been increasing, and years when it drops below the 37.4 degree threshold have become rarer. Also during this period, the parasite’s range has expanded to the north.
(Source: Cook, T et al (1998) The Relationship Between Increasing Sea-surface Temperature and the Northward Spread of Perkinsus marinus (Dermo) Disease Epizootics in Oysters. Estuarine Coastal and Shelf Science 46(4): 587-597 and Blander, K.M. 2007. “Global fish production and climate change.” Proceedings of the National Academy of Sciences 104(50): 19709-19714.)