Human health advisory on Back Creek,
Manokin River, Somerset County

Maryland's Pfiesteria Monitoring Activities:
August 20, 1999 Summary

Governor’s Press Release - Officials Advise Caution While Recreating on Back Creek off Manokin River in Somerset County.

The Governor’s Office released an advisory on August 18 for boating, swimming and recreating on Back Creek off the Manokin River in Somerset County. Potential health concerns are being examined and there has been no confirmation of toxic Pfiesteria .

DNR’s Resources Assessment Service has been collecting regular samples at approximately 50 locations in the Chesapeake and Coastal Bays for examination by Dr. David Oldach (University of Maryland Biotechnology Institute) with an experimental genetic technique designed to rapidly identify the presence of Pfiesteria piscicida. This sampling program is designed to determine the distribution of Pfiesteria in Maryland waters as well as alert the State to areas that may need additional surveillance. This technique does not differentiate between the toxic and non-toxic forms of the organism. The lack of distressed fish during each water sampling event where the test detects the presence of Pfiesteria strongly suggests that Pfiesteria was in one of its non-toxic forms. These results are not a reason for great concern, as previous experience has already demonstrated that non-toxic Pfiesteria exists in the waters of the Lower Eastern Shore.

Pfiesteria piscicida has been detected in the three Lower Eastern Shore river systems this summer: Pocomoke River, Transquaking River in the Chicamacomico River drainage and Back Creek in the Manokin River system. Results to date indicate none of the samples were toxic at the time of collection.

A water sample taken from the Pocomoke River on June 28 near Shelltown tested positive (See July 9 report) but subsequent sampling this summer has not found Pfiesteria again in this river. A sample taken from the Transquaking River on July 28 also tested positive for Pfiesteria piscicida. To follow up the July 28 test results, 6 samples were taken over an 11 mile stretch of the Transquaking River on August 12 and sent to cooperating labs by the Resource Assessment Service. Five of 6 samples tested positive in Dr. David Oldach’s genetic probe. Water samples were also sent to Dr. Burkholder’s and other labs for testing of toxicity. The first toxin test results reported on August 14 from Chris Dungan at the Oxford Laboratory were all negative for the Pfiesteria toxin. Fish collected from Transquaking River on August 10 appeared healthy; a collection on August 17 of 124 fish (77 were menhaden) comprised of 7 species found one menhaden with mild reddening, one with physical damage, and several with a gill parasite. All other fish appeared healthy.

On August 9, an individual who was out on Back Creek in the Manokin River system reported health concerns to Maryland’s medical surveillance team. DNR learned about this on August 10 and sent fish sampling crews on August 11. Fish collected in the area were healthy with no signs of lesions. Water samples were also collected. Dr. Oldach reported positive results for Pfiesteria piscicida, however, it appears densities were very low in that sample as Dr. Burkholder did not observe Pfiesteria-like cells in her analysis . On August 11, two individuals were in the same area of Back Creek reported a burning sensation when they put their hands in the water. DNR received this information on August 13. MD Natural Resource Police surveyed the area over the weekend and did not report anything unusual. Fisheries staff sampled the fish and water again on August 16 and all fish appeared healthy with no evidence of lesions. Water samples again tested positive for Pfiesteria at Dr. Oldach’s lab and elevated densities (i.e., 100-240 cells/milliliter) of Pfiesteria-like cells were observed by Dr. Burkholder. None of the samples has tested toxic. The samples sent to Dr. Burkholder are being incubated in fish and algal bioassays.

Three estuarine fish kills were found in Maryland between August 6 and 13 and investigated by MDE and DNR. Two kills involved carp, the largest kill (estimated at 600 carp on the Wicomico River, Western Shore) appeared to be affected by extreme low tidal conditions that could have caused stranding of the fish. Five live carp from the Wicomico River, Western shore, appearing lethargic were captured and taken to Dr. Ana Baya’s laboratory for analysis. Eighteen decomposing carp were found at Chesapeake Beach in Calvert County but no unusual water quality conditions were detected. A third incident with striped bass washed up on shore near the mouth of the Potomac River was believed to be discarded fish.

As of August 14, approximately 106,000 fish have been examined during fisheries sampling this year and low rates of anomalies on the total catch (<1.0%) continues to be observed. Over 2000 fish were collected from the Pocomoke River and its tributaries on August 13; no lesions were reported on any of the 80 menhaden. No lesions were found on the remaining 14 species totaling 2004 fish. The occurrence of lesions on menhaden in the Pocomoke region has remained low (< 1.5%) since the middle of June (see below).

a bar chart showing preliminary results for the Pocomoke River, 1999

During the first two weeks of August, 6252 young-of-the-year menhaden were collected from tributaries and embayments of the Tangier Sound. Nine percent (565) of the menhaden were observed with an external parasite on their gill plates known as an isopod. This is down from 32% during the last two weeks of July. The isopod is a type of crustacean. These menhaden with the isopods were collected from Pocomoke River, Chicamacomico River, Fishing Bay, Big Annemessex River, Wicomico River, Nanticoke River, Manokin River and Kings Creek and otherwise appeared healthy.

A reminder - please report fish kills, sick fish or fish with lesions to the Maryland Fish Health Hotline at 1-888-584-3110.

Weather patterns:
Rain storms fell across Maryland during the second weekend in August but severe drought conditions remain due to the lack of rain for the year. USGS reports that flow into the Bay in July was close to the minimum flow recorded for the month of July since 1951 and has remained well below average through the year. Stream flow at Nassawango Creek, a major tributary to the lower Pocomoke River, has been at below average levels for most of the summer based on the 49-year record, but spiked above average levels on August 14. Due to runoff from the weekend storms, water levels have remained above average levels through August 17. Until precipitation increases, the drought conditions and high temperatures coupled with nutrient enriched waters may continue to worsen low dissolved oxygen problems on the Lower Eastern Shore waters and other areas around the Bay, especially smaller creeks that may be poorly flushed.

Water Quality:
Salinity levels at the Lower Eastern Shore monitoring stations continue to be 2-4 ppt above average and in some cases have reached record high levels since 1985 when regular records have been kept for stations in Pocomoke Sound, Fishing Bay, the lower Manokin and Nanticoke Rivers. Elevated salinity has been associated with low river flows brought on by the drought. Salinity levels have been well above 1997 and 1998 levels for the same time of year at previous fish kill and lesion event locations on the Pocomoke and Chicamacomico Rivers (see graphs below).

The same trend appears in June and July comparisons of monitoring results on Back Creek in the Manokin River system between 1998 and 1999 (see bar chart below).

Daytime measures of dissolved oxygen were below the monthly averages for the long term, mid-channel monitoring stations on the lower Eastern Shore tributaries in July, but remained at levels acceptable for Bay fish in this region. On the Pocomoke River, dissolved oxygen levels in the surface waters between Pocomoke City and Pocomoke Sound have stabilized throughout most of the main river since during July and early August. A sag in oxygen levels, however, is developing just upstream of Shelltown (station POK0014) (see graphs below).

In Back Creek on the Manokin River drainage, dissolved oxygen levels have been comparable between 1998 and 1999 for June and July at the downstream station BXK0013; dissolved oxygen levels in 1999 at the upstream have measured above 1998 levels (see bar chart below).

Continuous water quality monitoring equipment is in place at 3 locations on the Pocomoke River (2 existing, 1 new) over the region of the 1997 fish kill to collect data every 15 minutes as part of EPA’s Environmental Monitoring for Public Access and Community Tracking (EMPACT).

Oxygen levels measured 1 meter below the surface in the lower Pocomoke River upstream of Shelltown at the Cedar Hall Wharf location increased to levels near 5 mg/L between July 15 and 30, with the exception of one night, on July 24, where oxygen values remained near zero for the entire night. During the last week of July, dissolved oxygen levels during the night, upstream at the Rehobeth station were commonly below 4 mg/L, with several measures below 3 mg/l. Such low oxygen levels can be lethal to fish, however, fish may also be displaced to regions of higher oxygen concentrations down river and farther out into Pocomoke Sound.

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