Caged Clam Study“Parks” and “Pond” Reaches, 2004

Thomas R. Benzing and Stacy DavenportJames Madison University

February 8, 2005

Clams taken from North River

Collecting clams (above) and sorting them by size (right)

Caging and Canoeing Clams

Clam Cage PlacementDooms

Hopeman Parkway

Basic Park

North Park

Mill Pond

Dates of Study

• Caged Clams: North Park to Basic Park– Placed on July 10, 2004– Recovered on September 25 (after 77 days)– 13 of 20 cages recovered (65%)

• Caged Clams: Dooms Mill Pond– Placed on July 16, 2004– Recovered on September 25 (after 71 days)– 18 of 20 cages recovered (90%)

FRANCES

IVAN

JEANNE

Cages recovered

Mercury in Caged Clams from Parks Reach

0

20

40

60

80

100

CCB0100

CCB0200

CCB0300

CCB0400

CCB0700

CCB0800

CCB0900

CCB1000

CCB1100

CCB1300

CCB1400

CCB1600

CCB1900

Site ID

Mer

cury

(ppb

)

Average Total Hg (ppb) Methyl Mercury

Parks Reach: Mercury by Site

WWTP outfall Oxbow

Parks Reach: Map of Mercury in Clams

North ParkBasic Park

2nd Street

Hopeman Parkway

Waynesboro wastewater

treatment plant

Total mercury concentrations

(ppb in clams) are shown by size of red symbol and numbers near cage locations US Route 340

Steele Run

Oxbow

Mercury in Caged Clams in South River in CCC Sites

0

20

40

60

80

100

120

140

160

180

200

220

CCC0000

CCC0200

CCC0300

CCC0400

CCC0500

CCC0600

CCC0700

CCC0800

CCC0900

CCC1000

CCC1100

CCC1200

CCC1300

CCC1400

CCC1600

CCC1700

CCC1800

CCC1900

Site ID

Mer

cury

(pp

b)

Average Total Hg Methyl Hg

Pond Reach: Mercury by Site

in mill pond

Pond Reach: Map of Mercury in Clams

Dooms

Mill Pond

mill dam

US Route 340

Total mercury concentrations

(ppb in clams) are shown by size of red symbol and numbers near cage locations

Conclusions from Caged Clam Study, 2004

• Mercury concentrations increase downstream from Dupont’s 001 outfall on South River in Waynesboro

• Mercury concentrations increase downstream from an oxbow (Steele Run confluence) near Basic Park

• Significantly higher mercury concentrations were found in the middle of the mill pond near Dooms

• In the mill pond, increases in methylmercury account for the increase in total mercury concentrations

• Caging clams allowed us to monitor locations where wild clams are not easily found (e.g. Dooms mill pond)

• Caged clams showed good survival rates (55.4 - 80.1%)• Some clam cages were lost during high flow (10 of 60)

Thanks to…Sina PriceliusStacy DavenportLee CochranCheryl HeatwoleTim ShenkAbsalom ShankFred Copithorn

Mark LottsPete BoltonAshley YoungHarrison GreenJacob HilemanBill Van WartTed Turner