Environmental Factors Influencing Benthic Polychaete Distributions in a Subtropical Lagoon

Abstract

AbstractFine-grained organic-rich sediments (FGORS) in the Indian River Lagoon (IRL), Florida, sometimes called “muck,” contain elevated water, silt-clay, and organic matter contents and are abundant as a result of anthropogenic nutrient inputs. Many polychaetes inhabit the benthic sediments of estuaries and tolerate various degrees of FGORS. FGORS composition can be variable, and its effects on infaunal life such as polychaetes may depend upon concentration and composition. The IRL Cox Muck Index (CMI) is proposed as a mechanism for assigning a single value to the complex composition of muck and found to be a useful tool for summary and comparison. CMI has negative correlations with polychaete density (R2 = 0.2, p < 0.001), richness (R2 = 0.57, p < 0.001), and diversity (R2 = 0.55, p < 0.001) based on multiple regression of principle components (PCs) derived from principle components analysis (PCA). Sediment with CMI of <1 fails to meet the definition of IRL muck in at least one parameter and is assumed capable of sustaining some metazoan life. The CMI range of 0.1‐0.2 supports the most robust polychaete community. The polychaete species Diopatra cuprea, Glycera americana, Alitta succinea, and Pectinaria gouldii persisted in the IRL above 0.6 CMI. An environmental dredging project removed muck sediments midway through this study and polychaete recovery following dredging was monitored. At one site, an area of Turkey Creek with abundant muck, the CMI was significantly reduced from 1.4 to 0.8 (p < 0.001). The developing polychaete community at these stations included G. americana and A. succinea. At the end of the study, there were increases in overall polychaete community density, richness, and diversity to 1,000 m−2, S = 3, H = 0.55, respectively.