THE EXPERIMENTAL ANALYSIS OF TIDAL CREEKS DOMINATED BY OYSTER REEFS: THE PREMANIPULATION YEAR

Abstract

We report here the experimental design and observations from the premanipulation year of an ecosyaem-level study investigating the hypothesis that oyster reefs control the structure and function of intertidal creeks. A group of eight tidal creeks in North Inlet, South Carolina, USA, dominated by oysters, Crassosrrea virginica (Gmelin), were studied using a replicated BACI (Before-After Control-Incident) design in which all creeks are sampled simultaneously. Before the start of the premanipulation year, oyster biomass in the creeks was adjusted to 8 g dblm? Detailed geomorphological observations were made on each creek as the study began. Nutrients and chlorophyll a were measured weekly in each creek and exhibited seasonal and interannual influences. Intensive planktonic-microbial loop samplings were conducted seasonally and suggested a diatom-dominated winter community controlled by nutrient availability and a microflagellate-dominated summer community controlled by grazing. Nekton biomass exceeded oyster biomass in most creeks during the summer. As expected, oyster growth decreased from summer to winler, and survival was higher in winter. In the study's second, or manipulation year, the role of oysters will be tested by removing them from four creeks.