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The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
Published on: August 3, 2016
Chesapeake Bay's "forgotten" Anacostia River: eutrophication and nutrient reduction measures
Caroline M Solomon1, Melanie Jackson2, Patricia M Glibert2
1Department of Science, Technology and Mathematics, Gallaudet University, 800 Florida Ave NE, Washington, DC, 20002, USA. caroline.solomon@gallaudet.edu.
Environmental Monitoring and Assessment
|April 7, 2019
Summary
The Anacostia River shows high nutrient levels and summer hypoxia. Pre-tunnel data reveal shifts in phytoplankton communities, with cyanobacteria increasing as nutrient conditions change.
Area of Science:
- Environmental Science
- Water Quality
- Ecology
Background:
- The Anacostia River, a tributary of the Chesapeake Bay in Washington, D.C., suffers from significant nutrient pollution.
- A large-scale tunnel project is underway to divert sewage effluent and improve water quality.
- Understanding the river's pre-intervention eutrophication status is crucial for assessing project effectiveness.
Purpose of the Study:
- To analyze nutrient and phytoplankton data over four years to determine the pre-tunnel eutrophication status.
- To investigate the relationship between nutrient concentrations, flow conditions, and phytoplankton community composition.
- To predict the potential impact of the tunnel project on algal blooms and community structure.
Main Methods:
- Analysis of biweekly to monthly nutrient (nitrate, ammonium) and chlorophyll a data over four years.
- Phytoplankton community assessment using pigment composition (zeaxanthin, fucoxanthin) to identify dominant groups (cyanobacteria, diatoms).
- Statistical analysis correlating nutrient levels, flow conditions, temperature, and phytoplankton abundance and type.
Main Results:
- Nutrient levels consistently exceeded growth-limiting values under all flow conditions.
- Summer hypoxia was observed, with higher chlorophyll a concentrations (26.9 μg L⁻¹) compared to spring (14.8 μg L⁻¹).
- Phytoplankton communities shifted, with a higher proportion of cyanobacteria in summer and diatoms in spring. Decreasing nitrate, increasing ammonium, and higher temperatures correlated with more cyanobacteria and fewer diatoms.
Conclusions:
- The Anacostia River was eutrophic prior to tunnel implementation, experiencing hypoxia and shifts in phytoplankton dominance.
- The tunnel project is expected to mitigate summer blooms, but potential impacts on spring phytoplankton assemblages, which occur during high flow, need consideration.
- Nutrient management strategies must address both overall load reduction and the specific nutrient ratios (e.g., ammonium to nitrate) influencing phytoplankton composition.
Keywords:
Combined sewer overflowCyanobacteriaFlow relationshipsNutrient pollutionWastewater treatmentMore Related Videos
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