Document Type

Thesis

Abstract

Oyster populations in the Chesapeake Bay have declined precipitously during the past century due to several factors, including overharvesting, increased sedimentation, and disease. By researching the Holocene distribution of oyster deposits, we can develop a baseline for restoration. This study addresses three research questions focusing on oyster shell deposits located near the Catlett Islands in the York River: 1) how has the percentage of oyster bottom changed over the past 100 years, 2) how does the distribution of buried shell relate to the distribution of surface shell and surface topography, and 3) what is the rate of degradation of oyster shell that remains exposed to brackish water post-mortem? To answer the first question, side scan sonar and single beam seabed classification were used, along with grab samples and video still shots to ground truth these data. By mapping the bottom and comparing it with historic data collected by the Baylor Survey in 1895, we were able to quantify how bottom type has changed due to increased sedimentation and overharvesting of oysters. For the second part of the project, we mapped the sub-bottom in this same region by computing subbottom profile data and collecting sediment cores. We also selected shells for radiocarbon dating from the cores to estimate how long shell deposition occurred in this area. The final part of this research involved a taphonomic experiment on shell degradation. A range of oyster sizes were deployed in the York River to determine the weight of shell organic content lost after one year. Given the prevalence of oyster restoration techniques that rely on cultch deployment and the fact that oyster spat do not settle on extremely degraded shell, this research will help determine how long oyster shell can remain viable for restoration.

Date Awarded

2007

Department

Geology

Advisor 1

Rowan Lockwood

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