Pfiesteria recorded from sediment samples
in four Maryland tributaries
May 21, 2001
This is the first report on Pfiesteria-related monitoring programs in Maryland for 2001.
Between January 8th and May 8th, 111 samples were collected and tested for Pfiesteria. All water samples collected from Maryland Chesapeake (Patuxent, Potomac, Rhode, Chicamacomico, Pocomoke River and Tangier Sound) and Coastal Bays (Trappe and Marshall and St. Martin Creeks) tributaries have tested negative for both forms of Pfiesteria.
Pfiesteria cells can be also be detected in the sediment. Sediment samples collected in November 2000 and April 2001 by the Maryland Geologic Survey are being analyzed by Holly Bowers and Dr. David Oldach at the University of Maryland Biotechnology Institute. Samples from twelve systems have been examined, with positive results for Pfiesteria species in some areas. (Table 1).
Table 1. Results of Pfiesteria surveys from sediment collections, Chesapeake and Coastal Bays, 2000 and 2001.
To date, Pfiesteria species have been detected in the sediment from four of the twelve systems surveyed in 2001; Fishing Bay, Middle River, Trappe Creek, and Marshall Creek. Interestingly, these four systems are the same sites as the major menhaden lesion events observed during 1999 and 2000. Large percentages of lesioned menhaden were observed for several week periods on Middle River in 1999 and Trappe and Marshall Creeks in 2000. Pokata Creek (a tributary of Fishing Bay) was the site of lesioned menhaden on several occasions in 2000. Pfiesteria was detected in the water column of all four of these systems while the lesion events were underway, although there was no evidence of active toxicity. These results suggest that Pfiesteria remains present in the sediment of systems for months to years after events that result in water column Pfiesteria activity.
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