COMPOSITION AND SOURCES OF SUSPENDED MATTER IN THE INDIAN RIVER LAGOON, FLORIDA

An increase in deposition of fine-grained, organic-rich sediment and a decline in seagrass abundance in the Indian River Lagoon System (IRL), Florida, are linked to increased inputs of total suspended solids (TSS). To learn more about the composition and sources of TSS in the IRL, samples were collected during fall 2003, spring 2004 and summer 2004 in the following areas: (1) southern Mosquito Lagoon, (2) IRL near Turnbull Creek, (3) Banana River Lagoon, (4) IRL near Turkey Creek and (5) IRL in Vero Beach. Concentrations of TSS ranged from 1.9–25.0 mg/L and correlated well (r = 0.95) with values for turbidity. Using selected chemical data, the average TSS in this study of the IRL were categorized as follows: (1) 18% terrestrial organic matter, (2) 30% organic matter produced in the lagoon, (3) 34% aluminosilicates/clays and (4) 18% other inorganic matter. Distinct differences in abundance, composition and likely sources of TSS were found geographically. These differences can be used to help guide decisions regarding management of TSS and to help better understand local variations in sedimentation patterns and seagrass abundance in the IRL.