Jump to main content or area navigation.

Contact Us

Extramural Research

Grantee Research Project Results

Grantee Research Project Results

Evaluating Anthropogenic Impacts Along the Land-Ocean Continuum Using Silica

EPA Grant Number: FP917238
Title: Evaluating Anthropogenic Impacts Along the Land-Ocean Continuum Using Silica
Investigators: Carey, Joanna
Institution: Boston University
EPA Project Officer: Jones, Brandon
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010)
Research Category: Academic Fellowships , Fellowship - Water Quality: Coastal and Estuarine Processes



Anthropogenic activities have greatly altered the global fluxes of nitrogen (N) and phosphorus (P) to coastal receiving waters. While N and P have appropriately received much research attention, another important nutrient, silica (Si), has largely gone unexamined and thus, Si cycling at the land-sea interface remains poorly understood. The purpose of this research is to examine how land use change alters the export of Si to New England estuaries.


Excess nitrogen and phosphorus in relation to silica can lead to a silica starved system, stimulating a shift in phytoplankton species composition from diatom to non-diatom species and altering tropic interactions. This research will quantify the impact of historic and current land use change on silica export from the terrestrial to the aquatic ecosystem and determine the relationship between current watershed land use and estuarine phytoplankton species composition and abundance.


This funding will quantify and characterize the type (dissolved vs. particulate) of Si, as well as N and P, exported via rivers from several New England watersheds with contrasting land use characteristics. In order to directly link watershed characteristics and downstream ecosystem response, concurrent phytoplankton composition and abundance measurements will be made in the receiving estuary (Plum Island Sound, MA). In addition, river sediment cores and historical land use data will help establish how the relationship between land use and watershed Si flux has changed in the recent past.

Expected Results:

This research will determine how land use change alters the export of Si via rivers, with attention to behavior of Si in relation to N and P and the impacts of such nutrient ratios on phytoplankton species composition in the receiving estuary. The resulting relationships between land use, river nutrient stoichiometry and phytoplankton species will provide new and critical insights into silica cycling at the terrestrial-aquatic interface.

Potential to Further Environmental/Human Health Protection:

Excess Nitrogen and Phosphorus can lead to Si-starvation in coastal waters, causing a shift in phytoplankton species composition from diatom to non-diatom species. The non-diatom species can be harmful algae blooms, such as red tides, which can alter higher trophic levels and, in some cases, are dangerous to human health. This research will provide important information for the management of coastal ecosystems.

Supplemental Keywords:

silica, eutrophication, land use, non-point source pollution, phytoplankton, diatoms, watershed, New England, Plum Island Sound, nutrient ratios, nitrogen, phosphorus,

Top of Page

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

Jump to main content.