Elevational stratification of oyster populations on subtidal oysterreefs in Virginia: Implications for interpreting monitoring efforts

摘要

It is widely recognized that restoration of oyster reef habitat in mid-Atlantic estuaries is requisite for restoring oyster fisheries and recovering lost ecologic services. As a result, considerable resources have been allocated to placing substrate on the seabed to promote oyster reef development. However, little effort has been devoted to evaluating the success of these efforts and, more importantly, to developing an understanding of how to improve these restoration practices. Recent research indicates that gross, and even subtle, characteristics of reef architecture can have dramatic effects on recruitment and survival of oysters. In an ongoing study in the Chesapeake Bay, we are making explicit comparisons between six restored reefs that differ in location, age, architecture, and management techniques in order to evaluate restoration approaches. A pattern of elevational stratification in oyster abundance is beginning to emerge, although this pattern varies between individual reefs. Because biologic processes (e.g., settlement and predation) may be affecting this pattern, it seems largely to result from physical transport of oysters on the unconsolidated reef veneers. Both reef architecture (e.g., slope) and hydrology (e.g., wave energy) seem to play a role in establishing the variation we observe across reefs in this pattern. We present evidence that these physical aspects may increase risks of negative impacts from large-scale disturbance events such as Hurricane Isabel that hit the region in 2003. Understanding how reef architecture and wave exposure affect the distribution of oysters on restored reefs will be important for designing future restoration projects and associated monitoring programs.