Relative Effects of Predation and Facilitation in Controlling the Distribution and Growth of an Intertidal Pulmonate Snail

EPA Grant Number: U915811
Title: Relative Effects of Predation and Facilitation in Controlling the Distribution and Growth of an Intertidal Pulmonate Snail
Investigators: Silliman, Brian R.
Institution: Brown University
EPA Project Officer: Michaud, Jayne
Project Period: October 1, 2001 through October 1, 2003
Project Amount: $102,000
RFA: STAR Graduate Fellowships (2000) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems


The overall goal of this study is to provide an in-depth understanding of how top-down and bottom-up forces interact to shape salt marsh community structure. The project's three main objectives are to: (1) initiate a long-term monitoring program on marsh grass growth and benthic microalgal biomass, N concentrations in the marsh porewater, and snail (Melampus bidentatus) densities; (2) determine the separate and interactive effects of Melampus grazing and N enrichment on marsh grass growth and microalgal biomass; and (3) determine how predator regulation of Melampus densities cascades downward to indirectly control marsh primary production.


To address these goals, a multifactorial experimental approach will be used involving manipulation of both snail and predator densities and the concentration of nitrogen in marsh porewater. Cages (n=8) will be used to manipulate animal densities, and plant and microalgae biomass will be measured as response variables. This research will be focused primarily on marshes within Narragansett Bay, Rhode Island. In addition, grass cover and food type will be manipulated both in the high and low marsh to investigate the role of marsh grasses in facilitating snail presence and growth. The effect of marsh grasses in buffering snails from predation, dessication, and drowning will be investigated.

Expected Results:

The results will allow managers to better predict potential effects of eutrophication and predator depletion (e.g., recent declines in crab populations) on salt marsh structure and function and to formulate effective long-term plans to sustain this resource.

Supplemental Keywords:

top-down control, positive interactions, nitrogen eutrophication, snails, Rhode Island, RI., RFA, Geographic Area, Water, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, State, Aquatic Ecosystem, algal blooms, wetlands, eutrophication, Narragansett Bay Time Series (NBTS), ecosystem monitoring, predators, marsh ecosystems, aquatic ecosystems, biochemical indicator , dissolved organic nitrogen, marsh ecosystem, Rhode Island (RI), nitrogen, intertidal pulmonate snail

Progress and Final Reports:

  • 2002
  • Final