Open canopy site	Collecting a surface-water sample	Collecting a surface-water sample	Processing water sample in the field	Closed canopy site

Introduction

The U.S. Environmental Protection Agency is developing guidance to assist states with defining nutrient criteria for rivers and streams and to better describe nutrient-algal relations. As part of this effort, during the summer of 2001 the NECB study sampled 13 wadable stream sites in the Boston, Massachusetts metropolitan area (Riskin and others, 2003). The 13 sites represent water-quality conditions that range from least impaired to impaired. These impairment conditions were determined on the basis of state regulatory agency assessments and available data on nitrogen, phosphorus, and dissolved oxygen. In addition, a combination of open- and closed-canopy locations were sampled at six of the sites to investigate the effect of sunlight on algal growth.

Purpose and study design

The objective of this study was to develop potential methods that could guide water-resource managers in the development of nutrient-criteria for New England streams on the basis of water-quality data collected at sites in the New England Coastal Basins (NECB) study area.

Each of the 13 stream sites was sampled on 5 occasions between June and September 2001. Streams were sampled during the summer in an effort to capture changes in biomass throughout the “growing season.” Water samples were analyzed for nitrogen and phosphorus species, and periphyton chlorophyll a. Field measurements for each sample included water temperature, dissolved oxygen, pH, specific conductance, and stream discharge.

General results

Among the 13 sites sampled, median nutrient concentrations were lowest at the 2 reference sites (least impaired) and highest at the 6 impaired sites. When sites were grouped by site type (reference, moderately impaired, and impaired), there were differences among all site types for total nitrogen and total phosphorus. Results of analysis of periphyton chlorophyll a concentrations from the 6 sites that had open- and closed-canopy sampling locations indicated that open-canopy locations had higher concentrations of chlorophyll a than closed-canopy locations among all three site types. Nutrient concentrations, types of substrates, and stream velocities were similar between the open- and closed-canopy locations at each of the 6 sites, indicating that light may have been the main factor affecting algal biomass as measured by chlorophyll a.

Further details and conclusions from the study are published in the report Nutrient and chlorophyll relations in selected streams of the New England Coastal Basins in Massachusetts and New Hampshire, June-September 2003 (U.S. Geological Survey Water-Resources Investigations Report 03-4191, 16 p. by Melissa Riskin, Jeffrey Deacon, Matthew Liebman, and Keith Robinson, 2003). The report is available in pdf format at: http://pubs.water.usgs.gov/wri034191

Reference

Riskin, M.L., Deacon, J.R., Liebman, M.L., and Robinson, K.W., 2003, Nutrient and chlorophyll relations in selected streams of the New England Coastal Basins in Massachusetts and New Hampshire, June-September 2001: U.S. Geological Survey Water-Resources Investigations Report 03-4191, 16 p.