In order to investigate the role of faunal aggregations in concentrating nutrients in the oligotrophic landscape of Florida Bay, I manipulated faunal densities in Florida Bay sea grass beds by constructing artificial reefs. The effects of reefs and faunal aggregations on nutrient availability and benthic community structure were assessed.
Over a year-long sampling period, artificial reefs had an average population of 50 fishes and crustaceans of various species. Faunal aggregation resulted in significant sediment organic matter decreases and sediment phosphorus increases. Plots with high fauna populations also had shorter seagrass blades presumably due to the effects of grazing. Chlorophyll-a concentrations in the sediment and periphyton samplers were mainly affected by reef presence or exclosure type and not due to the presence of aggregating fauna. Our results suggest that faunal aggregation may have more top-down effects on primary producers than bottom-up effects over smaller temporal scales.
