DEEP: Aquatic Life Impacts of Phosphorus Research

Aquatic Life Impacts of Phosphorus Research

Phosphorus is a nutrient that contributes to cultural eutrophication when added in excess to water bodies through human sources.  Cultural eutrophication is a serious threat to water quality in Connecticut and is also one of the most pressing water quality issues facing the nation.  Cultural eutrophication is described as human-caused acceleration of aquatic plant growth through excess nutrients, like phosphorus, in water bodies.  It is a process which leads to a heighten acceleration of primary production or biomass increases within a water body.  It causes harmful effects on water bodies, such as detrimental shifts in biological communities, fish kills, and reduction of dissolved oxygen and pH values.  Sources of human-inputs of phosphorus include waste water treatment facilities, lawn fertilizers, storm water runoff and agriculture.
{DEEP Monitoring Group staff examine excessive growth of filamentous green algae in Thompson Brook.}
Excessive growth of Cladophora, a filamentous green algae, in Thompson Brook.
Photo Credit CT DEEP Monitoring Program

The CT DEEP Monitoring Program is engaged in several efforts to study the effects of phosphorus in water bodies.  This website provides information on the monitoring efforts, results and analysis conducted by the Monitoring Program.  These efforts include recommendations by the Connecticut Academy of Science and Engineering report ‘Methods to Measure Phosphorus and Make Future Projections’ developed as part of Public Act 12-155, An Act Concerning Phosphorus Reductions in State Waters.

CT DEEP has taken several steps to implement reductions in the most impacted streams.  Information on the management of phosphorus in CT and Public Act 12-155 can be found on
Research Projects
Continuous Dissolved Oxygen Project
Primary Investigators – United States Geological Survey – Connecticut Office, CT DEEP Monitoring Program, and NEIWPCC
Status - Ongoing

The purpose of this project is to collect continuous dissolved oxygen data and evaluate the data for potential use in assessment of phosphorus effects in Connecticut streams on aquatic life.  Preliminary analysis from data collected in 2015 and 2016 show that daily dissolved oxygen flux (minimum-maximum for each day) may be a beneficial metric for assessment. Additional data is being collected to gain a better understanding of how dissolved oxygen varies as environmental conditions change (e.g. low flow vs high flow year).  Data collected under this project is quality assured by USGS and posted to the USGS NWIS database online.
Related Link: CT USGS Continuous Data Website
{CT DEEP Monitoring staff collect diatom samples from Cherry Brook.}
CT DEEP Monitoring Staff Collecting Diatom Samples from Cherry Brook.
Photo Credit CT DEEP Monitoring Program
Diatom Tolerance Metrics Project
Primary Investigator – CT DEEP Monitoring Program
Status - Ongoing
The CT DEEP monitoring program collects total phosphorus and algal community samples in rivers and streams. The type of algae collected are called diatoms.  Diatoms are good indicators of eutrophication in rivers and streams.  This data is being used to develop diatom tolerance metrics to assist in identifying phosphorus as a contributing cause of aquatic life impairment.  Biological tolerance metrics provide a measure of the sensitivity of aquatic organisms to anthropogenic disturbance, like phosphorus.  These metrics would be used in conjunction with other measures to identify phosphorus as a cause of aquatic life impairment. 
Ecologically Relevant Phosphorus Concentrations Project
Primary Investigators – U.S. EPA Office of Research and Develop and CT DEEP Monitoring Program
Status – Completed
Total phosphorus concentration thresholds were identified and evaluated for ecological relevance to diatom and algal biomass responses using a variety of methods.
Monitoring Plans
Reports and Presentations
For a complete list of reports and presentations related to the Aquatic Life Impacts of Phosphorus research project, refer to the "Nutrient Monitoring" section of the Monitoring Program Reports and Publications webpage.
Further Information
For questions or additional information please contact:
Mary Becker
Monitoring Program
Bureau of Water Protection and Land Reuse
Connecticut Department of Energy and Environmental Protection
79 Elm Street, Hartford CT 06106
Content last updated June 2018.