Herbivore Mediation of Nutrient Pollution in Seagrass Meadows

EPA Grant Number: F07B21147
Title: Herbivore Mediation of Nutrient Pollution in Seagrass Meadows
Investigators: Holzer, Kimberly K.
Institution: University of Virginia
EPA Project Officer: Lee, Sonja
Project Period: August 1, 2007 through July 31, 2010
RFA: STAR Graduate Fellowships (2007) RFA Text |  Recipients Lists
Research Category: Fellowship - Aquatic Ecology and Ecosystems , Academic Fellowships , Fellowship - Environmental


  1. To assess the influence of grazing (turtles and fish) and nutrients on patterns of production and biogeochemical processes in seagrass systems.
  2. To determine grazing (fish and snails) preference/intensity and consumer regulation of seagrass production along eutrophication gradients.
  3. To measure species-specific (snail) grazing preference/intensity and consumer impacts on low versus high nitrogen seagrass.


Unraveling the role of consumers in nutrient-perturbed seagrass ecosystems has both theoretical and applied value. Seagrass communities are declining worldwide, and much of this habitat deterioration is believed to be related to human activities which are altering the coastal zone at an accelerated pace through eutrophication and species exploitation (overfishing). To investigate herbivore (turtle, fish and snail) mediation of nutrient pollution in seagrass systems, I will use both field and laboratory experiments with natural and experimental variations in grazing pressure and nutrient supply including: simulated herbivory, nutrient enrichment, plant-tethering techniques and feeding assays.

Expected Results:

  1. Simulated turtle and fish grazing influence the effect of nutrient enrichment in seagrass meadows by altering patterns of production and biogeochemical processes.
  2. Although fish and snails prefer nitrogen-rich seagrass, consumer regulation of seagrass production is highest in nutrient-limited, slower growing offshore seagrass meadows.
  3. The emerald nerite snail prefers nitrogen-rich seagrass blades, which has negative consequences for seagrass biomass and plant photosynthesis.

Supplemental Keywords:

Seagrass, eutrophication, nutrient cycling, environmental chemistry, top-down vs. bottom-up control, Bermuda, green turtles, parrotfish, snails, trophic interactions, simulated herbivory, tethering, PAM, management,, Scientific Discipline

Progress and Final Reports:

  • 2008
  • 2009
  • Final