Distributions of Polychaetes as a Function of Sediment Composition in a Subtropical Lagoon
Fine-grained organic-rich sediments (FGORS) in the Indian River Lagoon (IRL), Florida, the human activities and nutrient inputs and have a varied composition, including water content, silt-clay content, and organic matter. When these constituents reach, by weight, 75%, 60% dry, and 10% dry, respectively, this is sometimes referred to as IRL “muck”. Many polychaetes inhabit the benthic sediments of estuaries and must tolerate various degrees of FGORS. The Cox IRL Muck Index (CMI) is proposed as a mechanism for determining the organic sediment tolerances of infaunal species in a simple and direct manner. IRL muck will have a minimum CMI of 1. The CMI most conducive to polychaete density, richness, and diversity is 0.2. CMI has negative correlations based on multiple regression of principles components derived from principle components analysis with polychaete density (R2=0.2, p<0.001), richness (R2=0.57, p<0.001), and diversity (R2=0.55, p<0.001). Diopata cuprea, Glycera americana, Alitta succinea, and Pectinaria gouldii persisted above >0.6 CMI. An environmental dredging project attempted to remove organic 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 falls within the range of that predicted by biological correlations with the CMI.