Abundance and Species Composition Surveys of Macroalgal Blooms in Rhode Island Salt Marshes

Excessive growth of macroalgae in estuarine systems is becoming increasingly common among coastal communities throughout the world. Despite repeated observations of macroalgae growing or deposited among the stems of lower marsh plants, few studies have quantitatively documented the presence of macroalgae in salt marsh communities. We conducted monthly surveys during 2009 and 2010 to document the species composition and abundance of the macroalgal community, along with associated biological and physical parameters, in 9 Rhode Island salt marshes. Macroalgae were found in every site during each month sampled, with a peak biomass during the fall, reaching densities up to 1500 g/m(2) (wet mass). Nearly 80% of the macroalgae was found in the first 2 m of the lower marsh zone. Fucus spp. were dominant throughout the year, accounting for almost 70% of the annual abundance. While several biological parameters were measured in this study that may contribute to macroalgal accumulation, it is likely that a combination of biotic and abiotic factors drive macroalgal accumulation patterns in these systems.