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.

Overview
In 1997, the occurrence of fish kills, fish health events and associated human health events were linked to the presence of toxic Pfiesteria piscicida on the Lower Eastern Shore of Maryland. The State Department of Natural Resources has initiated a new year of intensive monitoring for toxic outbreaks of Pfiesteria. Maryland DNR is once again coordinating Pfiesteria monitoring efforts with other agency and academic partners through the Pfiesteria Study Team as it has each year since the 1997 events. The Pfiesteria monitoring program is integrated with water and living resource quality assessments through the broader Chesapeake and Coastal Bays Monitoring Programs.

Pfiesteria 2001
Water samples have been collected since January and surveyed for Pfiesteria species (Pfiesteria piscicida and Pfiesteria shumwayae) using genetic probes developed by Dr. David Oldach (University of Maryland Biotechnology Institute). Genetic probes provide information on the presence or absence of Pfiesteria in the water column but do not tell us about its toxicity. Bioassays with live fish have been used for toxicity testing and faster toxicity test methods are still being researched and developed.

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.

Waterbody

Month and year of collection

Percent positive for P. piscicida (sample size)

Percent positive
for P. shumwayae
(sample size)

Choptank River

November 2000 & April 2001

0 (12)

0 (12)

Honga River

November 2000

0 (12)

0 (12)

Fishing Bay

November 2000

16.7% (2 of 12)

0 (12)

Pocomoke River

November 2000

0 (12)

0 (12)

Nanticoke River

November 2000

0 (12)

0 (12)

Middle River

November 2000

75.0% (9 of 12)

0 (12)

Patuxent River

November 2000

0 (12)

0 (12)

Potomac River

November 2000

0 (12)

0 (12)

St. Mary’s River

November 2000

0 (12)

0 (12)

Trappe Creek (Coastal Bays)

April 2001

0(12)

16.7% (2 of 12)

Marshall Creek (Coastal Bays)

April 2001

33.3% (4 of 12)

83.3% (10 of 12)

St. Martin
(Coastal Bays)

April 2001

0(12)

0(12)

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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