Implications of high-resolution geophysical techniques in oysterhabitat identification: Cape Fear River, North Carolina

摘要

Eastern oysters (Crassostrea virginica) are filter feeding organisms that settle in dense aggregates and positively impact water quality by providing a series of ecosystem functions, which include habitat for other organisms, filtration, and habitat stability. The United States Army Corps of Engineers created dredge spoil islands throughout the lower 20 km of North Carolina's Cape Fear River as a result of channel dredging. These activities have altered water flow and increased siltation, reducing the amount of hard substrate available for oyster spat settlement and growth. Currently, small amounts of hard substrate remain in the lower river and routinely experience high overspat events, followed by high mortality from a combination of competition and high sedimentation. Sidescan sonar and sub-bottom profiling systems were used to map four areas within a 15 km long section of the lower Cape Fear River to locate living and buried oyster reefs. The southernmost area contains living oysters, while the northernmost areas are along dredge spoil islands and are devoid of living populations, despite the presence of Indian middens, which may suggest a localized historic occurrence of oysters and the potential for buried oyster reefs. Potential buried reef locations have been identified for ground-verification. Hypothesizing that oysters should be able to grow where they once thrived, these data will be used to guide placement of oyster cultch. If these sites prove suitable for new oyster cultivation, this geophysical technique has important implications for the success of future oyster restoration projects in southeastern North Carolina.