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Abstract

During the summer and early fall of 1998, 34 estuarine stations in Virginia were sampled for Pfiesteria like organisms (PLOs) and associated water quality conditions. Stations were sampled either bimonthly (20 stations) or monthly (14 stations) from June to October 1998. At each station, a set of live and Lugol' s preserved samples were collected for presumptive counts of PLOs and water quality conditions were determined. Water quality parame­ters measured included standard field parameters, nutrients (total, dissolved, and particulate), chlorophyll a, and conventional water quality indicators. Although PLOs were relatively low in 1998 as compared to 1997, presump­tive PLO counts revealed higher PLO levels at stations located in the Northern Neck area (Potomac Embayments, Rappallannock River, and other smaller watersheds). The water quality parameters of pH, dissolved oxygen, and temperature were correlated with higher PLO counts, while several nutrients, salinity, and turbidity ,vere negatively correlated with PLOs. In the August 1997, relatively minor fish kills in the Pocomoke River and the Pocomoke Sound on the Virginia and Maryland border were attnbuted to the toxic dinoflagellate, Pfiesteria piscicida. Pfiesteria piscicida was first identified as a fish-killing dinoflagellate in fish tank at North Carolina State University (Noga et al., 1993 ). Pfiesteria piscicda has since been implicated in large widespread fish kills in North Carolina's estuaries (Burkholder et al., 1992, 1995).

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