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Project ID: 2004NC36B

Title: Is There a Relationship Between Phosphorus and Fecal Microbes in Aquatic Sediments?

Project Type: Research

Focus Categories: Non Point Pollution, Nutrients, Sediments

Keywords: Phosphorus, Bacteria, River Beds, Stormwater Management, Watershed Management

Start Date: 03/01/2004

End Date: 02/28/2005

Federal Funds: $23,169

Non-Federal Matching Funds: $46,337

Congressional District: 7

Principal Investigators:
Lawrence B. Cahoon

Michael A. Mallin


Recent research, including some of our own work in estuarine ecosystems, shows that sediments frequently support populations of fecal coliform bacteria at concentrations high enough to close the overlying waters for human uses if resuspended. A number of studies have now shown that phosphorus may be particularly important in supporting the persistence and re-growth of fecal coliform bacteria in sediments. Phosphorus has a strong affinity for particulates, so the bulk of phosphorus loaded into aquatic ecosystems is associated with sediments. We propose to test the hypothesis that phosphorus pollution may actually enhance the problems caused by fecal contamination of aquatic ecosystems. If true, then measures to control phosphorus pollution will take on added urgency.

We propose using a combination of observational and experimental approaches to test this hypothesis. Our observational approach would consist of collecting sediment samples in winter and summer from a large set of sites in the lower Cape Fear River basin as well as in watersheds of New Hanover County and the City of Wilmington, all of which are monitored regularly for water quality parameters as part of several separately funded, ongoing monitoring programs. Sediment samples would be analyzed for fecal coliform and fecal enterococcus bacteria, two commonly used indicators of fecal contamination, using standard microbiological techniques. Sediment samples would also be analyzed for phosphorus content, using a standard fractionation technique for distinguishing among soluble, adsorbed, soluble organic, particulate, and refractory forms of phosphorus. We would test for significant correlations between the sediment fecal contamination measures and the sediment phosphorus concentration measures. We would also use multivariate procedures (PCA and a posteriori correlation tests) to examine relationships between the larger monitoring data sets and our measured sediment variables. Our experimental approach would entail manipulation of sediment samples with added phosphorus in laboratory experiments to examine the responses of sediment-associated fecal bacteria populations. We would use sediment samples from a selected subset of monitoring locations in a randomized, factorial design employing four levels of added phosphorus and adequate replication based on preliminary analyses of fecal bacteria variability in the sediments. Results would be analyzed by ANOVA.

Progress/Completion Report PDF

U.S. Department of the Interior, U.S. Geological Survey
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