Comparison of Clam Data, 2001-2003

Sampling Location ID C S 18 C S 10 1 C S 40 1

C S 17

C S 16

C S 15

C S 14

C S 13

C S 12

C S 11

0.45

C S 10

C S 09

C S 08

C S 07

C S 06

C S 05

C S 04

C S 03

C S 02

C S 01

Hg Concentration (ppmwet weight)

Comparison of Clam Data, 2001-2003

0.60

2003 2002 2001

0.30

0.15

0.00

Proposal for Caged Clam Study, Summer 2004 Thomas R. Benzing James Madison University April 14, 2004 Presentation to SRST

South River watershed and clam sites

Plant area and clam sites

Plant area and 2002 Hg data for Corbicula

Plant area and proposed cage sites (Option A)

North Park to Basic Park and clam sites

North to Basic and 2002 Hg data for Corbicula

North to Basic and proposed cage sites (Option B)

Dooms Mill Pond and clam sites

Dooms Mill Pond and 2002 Hg data for Corbicula

Dooms area and proposed cage sites (Option C)

Considerations for selecting option A, B, or C

• Significant differences in Hg measured within river reach • Accessibility issues (placement and retrieval, vandalism) • Clam habitat and survival issues • Occurrence of “mud” and likely Hg methylation areas • Other issues to consider?

Clam Tissue Results, 2003

0.40

Total Hg Methyl Hg Hg Concentration (ppmwet weight)

0.30

Methyl Hg = 38% Total Hg 0.20

0.10

0.00 CS01

CS03

CS12

CS18

Sampling Site ID

CS101

CS401