| Seagrass meadows are valuable habitats for all of the ecosystem services that they provide, including food and shelter for commercially important fisheries species, water quality enhancement, sediment stabilization, and nutrient and carbon dioxide sequestration. There is mounting evidence that top-down forces, such as grazing and predation, are much more important in controlling seagrass abundance and distribution than previously recognized. Even so, little is known about how the unique feeding modes of different seagrass consumers affect seagrass biomass and growth. We also lack a clear understanding of how resource availability (e.g. nutrients) influences plant responses to herbivory in seagrass meadows. The objectives of this dissertation were to: (1) To determine the effect of green turtle grazing on seagrass growth and food quality (foliar nitrogen) in low and high nutrient environments. (2) To compare bucktooth parrotfish grazing pressure and preference in low and high nutrient environments. (3) To clarify differences in direct versus indirect grazing by snails on seagrass biomass and growth. All three objectives had the underlying goal of assessing whether herbivory could have influenced recently documented, large-scale declines in Bermuda's seagrass area. |
