1. Transplanted Oyster (Crassostrea virginica) Beds as Self-Sustaining Mechanisms for Water Quality Improvements in Small Tidal Creeks: A Pilot Study Kimberly A. Nelson

2. OYSTER FILTRATION  Oysters filter up to 120 L of H 2 O daily.  In flume studies, oysters may remove up to 50% of the seston from the overlying water column.  Oysters may decrease the risk of eutrophic conditions, thereby improving light penetration and water clarity.  Oysters filter up to 120 L of H 2 O daily.  In flume studies, oysters may remove up to 50% of the seston from the overlying water column.  Oysters may decrease the risk of eutrophic conditions, thereby improving light penetration and water clarity.

3. HYDRODYNAMICS Flow Low Velocity “Shadow Zone” REEF Increased turbulence at reef crest Increased flow velocities at reef crest Low velocity “shadow zones” downcurrent and on reef edges Increased turbulence at reef crest Increased flow velocities at reef crest Low velocity “shadow zones” downcurrent and on reef edges

4. OYSTER RESTORATION Current Methods Large subtidal reefs of high- relief, to improve reef health and survival. Current Methods Large subtidal reefs of high- relief, to improve reef health and survival. PROBLEMS 1.Subtidal reefs may not allow the majority of the water column to reach the benthos for filtration. 2.High velocities may decrease filtration capabilities. PROBLEMS 1.Subtidal reefs may not allow the majority of the water column to reach the benthos for filtration. 2.High velocities may decrease filtration capabilities. Piankatank River, Virginia

5. Establish self-sustaining oyster reefs in two small tidal creeks. Examine hydrodynamic changes associated with the placement and subsequent growth of the oyster reefs. Investigate downstream changes in suspended particulate matter, chlorophyll a and ammonium as function of reef placement and growth. Establish self-sustaining oyster reefs in two small tidal creeks. Examine hydrodynamic changes associated with the placement and subsequent growth of the oyster reefs. Investigate downstream changes in suspended particulate matter, chlorophyll a and ammonium as function of reef placement and growth. OBJECTIVES

6. STUDY AREA UPLAND LOWER CREEK

7. REEF PLACEMENT: September 2000 2 m X 3 m PVC frame with hardware cloth Mature oysters (3”) 125 live oysters per m 2 REEF PLACEMENT: September 2000 2 m X 3 m PVC frame with hardware cloth Mature oysters (3”) 125 live oysters per m 2 METHODS

8. WATER QUALITY ANALYSIS Monthly Samples Total Suspended Solids (TSS) Chlorophyll a Ammonium Ebbing Tide 1 m 3 m REEF 4-6 cm 5 cm

9. SAMPLING SCHEME – Upland Flow Measurements Reef Channel Profile Sediment Analysis Reef Characteristics Density Growth Mortality Flow Measurements Reef Channel Profile Sediment Analysis Reef Characteristics Density Growth Mortality

10. OYSTER PARAMETERS 0 10 20 30 40 50 60 70 Aug - 00Dec - 00Jun - 01 Mean size (mm) length width Total mortality % survivorship DEC - 00 JUN - 01 20.3 % 43.8 % 79.7% 56.1 %

11. Mean TSS - Lower Creek Reef Control TSS mg L -1 Above Below TSS mg L -1 * Reef & Control Channels Above & Below Reef

12. Mean TSS – Upland Reef Control TSS mg L -1 ** Above Below Reef & Control Channels Above & Below Reef

13. CHLOROPHYLL a Phytoplankton is the preferred food source of Crassostrea virginica. Oysters may deplete 20 to >75% of chlorophyll a concentrations from the particulate supply over oyster beds in flume studies. By active filtration of phytoplankton and nutrients (phosphate, nitrogen, silica), oysters may decrease the potential for eutrophication in estuaries.

14. Mean Chlorophyll a – Lower Creek Chl a µg L -1 Reef & Control Channels Above & Below Reef Reef Control Above Below

15. Mean Chlorophyll a - Upland Chl a µg L -1 Reef Control Chl a µg L -1 Above Below Reef & Control Channels Above & Below Reef

16. FLOW DYNAMICS Velocity Discharge Max impact

17. Reef Control Hour 3 Hour 3 Chlorophyll a - Lower Creek Reef to Control Channels Chl a µg L -1

18. Hour 3 Chlorophyll a - Lower Creek Above to Below Reef Chl a µg L -1 Above Below

19. Reef Control Hour 3 Hour 3 Chlorophyll a - Upland Reef to Control Channels Chl a µg L -1 *

20. Hour 3 Chlorophyll a - Upland Above to Below Reef Chl a µg L -1 Above Below * * *

21. AMMONIUM (NH 4 + ) After consumption and processing, seston is deposited as feces or pseudofeces. Oysters may contribute 15 to 40% of the dissolved organic nitrogen within in situ domes. After consumption and processing, seston is deposited as feces or pseudofeces. Oysters may contribute 15 to 40% of the dissolved organic nitrogen within in situ domes.

22. Ammonium - Lower Creek Reef to Control Channels Ammonium µg L -1 Reef Control

23. Ammonium - Lower Creek Above to Below Reef Ammonium µg L -1 Above Below

24. Ammonium - Upland Reef to Control Channels Ammonium µg L -1 Reef Control

25. Ammonium - Upland Above to Below Reef Ammonium µg L -1 Above Below

26. Hour 3 Hour 3 Ammonium - Lower Creek Reef to Control Channels Ammonium µg L -1 Reef Control

27. Hour 3 Ammonium - Upland Above to Below Reef Ammonium µg L -1 Above Below

28. Hour 3 Hour 3 Ammonium - Upland Reef to Control Channels Ammonium µg L -1 Reef Control

29. GRAIN SIZE ANALYSIS 0 1 2 3 0.1110100100010000 Particle Diameter (  m) Volume (%) 0 1 2 3 0.1110100100010000 Particle Diameter (  m) Volume (%) Reef Matrix16.40103.8 Downstream19.76130.0 Upstream140.1120.2 Control140.1152.4 Reef Matrix16.40103.8 Downstream19.76130.0 Upstream140.1120.2 Control140.1152.4 Mode(µm)Mean(µm)

30. LAST THOUGHTS Small, viable oyster reefs can be established and maintained over periods of at least ten months duration in small upland tidal creeks. An optimal ratio of reef size to flow discharge exists whereby filtration is maximum. Additional studies are needed to determine the volume of reef ratio and the reef geometry that would achieve desired results utilizing maximum resources. Small, viable oyster reefs can be established and maintained over periods of at least ten months duration in small upland tidal creeks. An optimal ratio of reef size to flow discharge exists whereby filtration is maximum. Additional studies are needed to determine the volume of reef ratio and the reef geometry that would achieve desired results utilizing maximum resources.