Productivity and biomass of Thalassia testudinum as related to water column nutrient availability and epiphyte levels: field observations and experimental studies

Abstract

Turtlegrass Thalassia testudinum meadows from 0.5 m and 2.0 m depths were studied in the Florida Keys and W Caribbean. Two meadows, one offshore of a populated island with over 2000 septic tanks, and one offshore of a large bird rookery, were similar in having elevated levels of water column nutrients, greater epiphyte levels, low shoot densities, low leaf area indices, and low biomass. Increased blade turnover time was partially responsible for increased epiphyte levels offshore of the populated island, but epiphyte communities developed faster on seagrass blades there than at a paired site offshore of an uninhabitated island. Reduced irradiance moderated the effect of nutrient enrichment on epiphyte levels. Elevated levels of water column nutrients, by stimulating epiphyte growth, reduced rhizome growth rates. -from Authors