Interaction Between Grazing and Nutrients as Controls of Macrophyte Biomass and Community Structure in Shallow Temperate Estuaries

EPA Grant Number: U915335
Title: Interaction Between Grazing and Nutrients as Controls of Macrophyte Biomass and Community Structure in Shallow Temperate Estuaries
Investigators: Hauxwell, Jennifer A.
Institution: Boston University
EPA Project Officer: Michaud, Jayne
Project Period: September 1, 1998 through January 1, 1999
Project Amount: $61,632
RFA: STAR Graduate Fellowships (1998) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems


The objective of this research project is to determine how anthropogenic nitrogen inputs, grazing by benthic invertebrates, and competitive interactions between macroalgae and seagrasses influence macrophyte biomass and community structure (seagrass- or macroalgal-dominated) in shallow temperate estuaries.


I will collect experimental and descriptive field data from different estuaries of Waquoit Bay, MA, that are exposed to different nitrogen loads. I will conduct monthly benthic surveys for 1 year to assess macroalgal and eelgrass biomass and areal coverage, and invertebrate grazer abundances. Additional field data will include annual eelgrass growth rates and shoot density to allow an estimation of production. I will model grazer impact on macroalgal biomass based on survey data, field grazing rates by abundant herbivores on their algal foods, and in situ macroalgal growth measurements. To examine the effect of grazers and nitrogen-loading rates on epiphytes of eelgrass, I will determine: (1) the epiphyte load of eelgrass in estuaries exposed to differing nitrogen loads; (2) the effect of epiphytes on eelgrass growth in these estuaries; and (3) the effect of grazers on epiphyte biomass. I will conduct field-shading experiments in which I exclude macroalgae from plots of eelgrass or include macroalgae at differing canopy heights (corresponding to different nitrogen loads), and measure the impact on eelgrass density and growth to examine the interaction between macroalgal canopies and eelgrass production. The results will allow a synthesis of control processes that govern how macrophytes and grazers interact in shallow water coastal ecosystems, how controls seasonally vary, and how the grazer/macrophyte system is coupled to external anthropogenic inputs of nutrients from adjoining terrestrial ecosystems.

Supplemental Keywords:

fellowship, macrophyte biomass, anthropogenic nitrogen inputs, benthic invertebrates, macroalgae., RFA, Scientific Discipline, Geographic Area, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, State, Aquatic Ecosystem, Ecology and Ecosystems, estuarine research, macroalgal blooms, macrophyte biomass, nitrogen cycling, benthic marine invertibrates, Massachusetts (MA), anthropogenic impact, aquatic plants, aquatic ecosystems, estuarine waters, benthic invertebrate patterns

Progress and Final Reports:

  • Final