Monday, November 13, 2006

Environmental Conditions Affecting Seagrass Growth in a Constructed Habitat: a Study of Light, Hydrodynamics and Subaqueous Soils in the Indian River Lagoon, Fl.

Kelly Fischler, M.E. Collins, L.R. Ellis, and G.R. Keehn. Univ of Florida, 2169 McCarty Hall, Gainesville, FL 32611

In the Indian River Lagoon, FL, spoil island SL 15 (St. Lucie County) was scraped down to create a 1.7 ha submerged habitat for seagrass mitigation.  SL 15 created a unique chance to examine how different ecological parameters might interact and affect future seagrass colonization.  Light, nutrient and hydrodynamic conditions inside the habitat were compared to conditions in surrounding seagrass beds. Relationships between subaqueous soils and seagrasses were examined through the creation of a fine-scale soil survey and digital elevation model.  The recently exposed bottom within SL 15 consists of four types of soil: a coarse carbonate spoil material, a fine-textured mangrove clay, an accreted flocculent layer, and a buried seagrass A horizon which was present before SL 15 was created.  Surface soil properties appear to be correlated with elevation and hydrodynamics.  A transplant experiment was also conducted within and outside of the island, using differences in soil type as the variable of interest.  Currently, four species of seagrasses have colonized the habitat and grow within each soil map unit. By synthesizing the environmental data, soil descriptions and transplant results into a habitat suitability model and comparing it to the current distribution of grasses, inferences can be made as to the importance of different ecological variables in a constructed habitat.