Stream Nutrients Project

Background

Eutrophication of freshwater ecosystems resulting from nitrogen and phosphorus pollution is an issue across the globe. Despite recognition of the problem by scientists and stakeholders, decision-makers still need rigorous synthesis of scientific evidence for nutrient management, especially in streams and rivers. Drawing inferences about how nitrogen and phosphorus concentrations affect stream biota is complicated by:

• Exposure to multiple interacting environmental factors;
• Complex and indirect causal pathways involving diverse organisms;
• Legacy (historic) nutrient sources; and
• The naturally high spatial and temporal variability of running water systems.

The Stream Nutrient Project aims to empower stakeholders to identify, manage, and restore streams and rivers impaired by eutrophication and maintain currently unimpaired systems. A critical first step is to determine the nutrient levels that affect ecosystems.

Nutrient Systematic Reviews

EPA conducted systematic reviews of the scientific literature to examine how nutrient stressors affect algae and macroinvertebrates in stream and river ecosystems. These reviews comprehensively synthesized published studies investigating how total nitrogen and total phosphorus concentrations affect three biological responses:

1. Chlorophyll a (benthic and sestonic);
2. Diatoms; and
3. Benthic macroinvertebrates.

The Stream Nutrients Project collates the evidence records created in these reviews and makes them available to EcoDIVER users. After screening thousands of articles, we identified nearly 300 relevant documents, published from 1972-2018. Each of these documents reported at least one quantitative relationship between nutrient stressors and biological responses. We created evidence records by extracting more than 200 categorical and quantitative fields of information for each of these relationships.

View the Evidence

Tips for viewing and interacting with the visualizations

• If possible, view the visualizations on a laptop or desktop computer using the maximum window size. When using a mobile device or viewing the visualizations in a small window, the layout may change (e.g., new panels may display below the initial panel rather than to the right of the initial panel) and titles or axis labels may be cut off. Remember to scroll right and/or down in the window to see visualizations in their entirety.
• You may see empty boxes when you first click on the heat map or modified boxplot visualizations, as the visualization retrieves the data. There may also be a short delay for maps and distribution plots to update as filters are applied.
• Each visualization includes helpful information on how to view and interact with that visualization, under either the blue Help button at the top right of the visualization (for the heat map, box plot, and forest plot visualizations) or in the text at the top of the visualization (for the map-based and histogram visualizations). Please read this information before interacting with the visualizations.
• The heat map and modified boxplot visualizations all work in the same general fashion: (i) an initial figure is displayed at the left; (ii) hovering over a cell or panel in that figure displays relevant summary information; and (iii) clicking on a cell or sample size (n) value in that figure displays a data table or additional figure at the right (or below, if you are viewing the visualization in a small window).
• If you scroll when your cursor is hovering over plots in the map-based and histogram visualizations, you will zoom in/out on these plots to view information at different scales.
• See the Stream Nutrients Visualization Guide page for additional information on how to navigate specific visualizations.

What are you interested in?	Visualization Type	Description/Link	Thumbnail
Nutrient stressor-biological response evidence by country	Map-based summary of evidence base	World overview of evidence base for all nutrient stressor-biological response relationships
Nutrient stressor-biological response evidence by EPA region	Map-based summary of evidence base	EPA region overview of evidence base for all nutrient stressor-biological response relationships
Nutrient stressor-biological response evidence by US state	Map-based summary of evidence base	State overview of evidence base for all nutrient stressor-biological response relationships
Other environmental conditions	Bar charts and distribution plots	Filterable bar charts and distribution plots of environmental conditions under which nutrient stressor-biological response relationships were measured
All biological responses by geographic location	Heat map	Heat map of citations for each nutrient stressor-biological response combination, filterable by country or US state
Chlorophyll a summary effect sizes	Box plot	Box plot of summary effect sizes and citations for 4 nutrient stressor-chlorophyll response relationships
Chlorophyll a summary effect sizes by geographic location	Box plot	Box plot of summary effect sizes and citations for 4 nutrient stressor-chlorophyll response relationships, filterable by country or US state
Chlorophyll a individual study effect sizes	Box plot + forest plot	Box plot of summary effect sizes and forest plot of effect sizes by citation for 4 nutrient stressor-chlorophyll response relationships
Chlorophyll a individual study effect sizes by geographic location	Box plot + forest plot	Box plot of summary effect sizes and forest plot of effect sizes by citation for 4 nutrient stressor-chlorophyll response relationships, filterable by country or US state
Chlorophyll a summary effect sizes by year of publication	Box plot	Box plot of summary effect sizes and citations for 4 nutrient stressor-chlorophyll response relationships, filterable by year of publication
Chlorophyll a individual study effect sizes by year of publication	Box plot + forest plot	Box plot of summary effect sizes and forest plot of effect sizes by citation for 4 nutrient stressor-chlorophyll response relationships, filterable by year of publication