Eutrophication Research Plan

View SCCWRP’s full thematic Research Plan for Eutrophication (PDF)

2022-2023 Executive Summary

Nutrient pollution and other anthropogenic activities that result in increased temperatures, physical habitat and hydrological alteration can trigger eutrophication, which is accelerated accumulation of organic matter from overgrowth of aquatic plants and algae. These aquatic blooms can be unsightly and, in some cases, produce toxins and noxious odors. They can also lead to low dissolved-oxygen and pH levels that trigger declines in fishery harvests and in diversity of aquatic life. However, determining the nutrient load a water body can sustainably assimilate is challenging because, unlike with contaminants, some level of nutrient input is necessary to sustain life. Climate change is altering CO2 levels, temperature regimes, and modifying freshwater inputs, all of which can exacerbate eutrophication driven by local land use changes. SCCWRP is working to characterize the extent of the problem, particularly focused on toxic bloom species, and the bioaccumulation of their toxins in the food web. We are conducting process studies and develop and validate models that link eutrophication drivers to adverse outcomes. These models can be used to develop comprehensive eutrophication management strategies, including the ability to pinpoint when and where eutrophication is likely to occur and which strategies, including nutrient management and ecosystem restoration, might be the most cost effective.

Management applications are in the forefront of this work. In inland waters, SCCWRP is serving as the technical lead on a multi-year effort by the State Water Board to develop a combined biostimulatory (i.e., nutrient) and biointegrity policy to protect California’s wadeable streams, lakes and estuaries. Wadeable streams and lakes are the current priority for the first phase of this policy. SCCWRP is also supporting the development of comprehensive eutrophication and harmful algal bloom monitoring protocols to protect human and ecosystem health, including both remote sensing and field-based methodologies. Of particular focus are methods that lend themselves to successful implementation by citizen science programs. In coastal waters, SCCWRP is studying if and how anthropogenic nutrient inputs to the California Current ecosystem are contributing to eutrophication, particularly with respect to increasing algal blooms and declines in dissolved oxygen and pH, and declines in habitat for submerged aquatic vegetation such as kelp and seagrass. 

This year, SCCWRP research will continue building a knowledge base that allows nutrient loading, HABs and eutrophic events to be more effectively monitored and managed in California, both in fresh and marine waters. SCCWRP’s focus for 2022-2023 will be on:

  • Building the technical foundation for eutrophication targets in California water bodies: SCCWRP is pursuing a multi-pronged approach to build the technical foundation upon which policy decisions regarding biointegrity, nutrient and eutrophication targets for California’s wadeable streams, lakes and estuaries will be based. This year, SCCWRP will continue to advance the science supporting the State’s proposed biostimulatory/biointegrity policy, which is intended to govern the health of wadeable streams, lakes and estuaries. This ongoing work includes refining statistical models that link algal and benthic macroinvertebrate community composition to pathways of eutrophication impacts; these models will support State decision-making on eutrophication (a.k.a. biostimulatory) targets. SCCWRP also will continue its work to support policy discussions for biostimulatory targets in lakes, including developing statistical models that relate harmful algal bloom and hypoxia endpoints in lakes to eutrophication gradients of nutrients and chlorophyll-a; this work is being coupled with landscape models that predict how land use and other remotely sensed data influence eutrophication risk. Finally, SCCWRP will continue demonstration projects illustrating how to apply a combined biostimulatory/biointegrity approach to watershed management decision support, with case studies in the Santa Margarita, San Joaquin and Sacramento River watersheds.
  • Assessing harmful algal blooms: To understand the magnitude and spatial extent of HABs across marine, estuarine and freshwater systems, SCCWRP is studying the ecophysiological factors that drive HABs initiation and proliferation. SCCWRP is continuing its focus on: (1) supporting the State in implementing a comprehensive inland freshwater HABs monitoring and assessment program, including building monitoring methodology, infrastructure and coordination; (2) conducting field-based and remotely sensed status and trends assessments of HABs in lakes, streams and estuaries, including pinpointing which HAB organisms are present and which toxins are being produced; (3) comprehensively characterizing HAB drivers, including nutrients, temperature and hydromodification, and how these drivers trigger the production of toxins; (4) identifying factors that influence fate and transport of HAB toxins that are measured in edible shellfish and other organisms; and (5) supporting development of mechanistic numerical HAB models for estuaries and the California coastal ocean.
  • Biogeochemical effects of anthropogenic nutrients and carbon in the Southern California Bight: SCCWRP will continue working with West Coast researchers to apply coupled physical oceanographic and biogeochemical models to examine how regional carbon dioxide emissions and discharges of land-based nutrient sources into the Southern California Bight and other locations along the California Coast are influencing coastal ocean acidification, hypoxia and HABs. SCCWRP and collaborators will be using the models to: (1) quantify causal linkages to particular sources (point source vs. non-point source) and pathways (river runoff vs. atmospheric deposition vs. ocean outfalls); (2) simulate alternate scenarios for wastewater nutrient management and water recycling to predict the efficacy of various management strategies to reduce eutrophication; and (3) explore how global climate change is altering the ocean state and how these changes influence anthropogenic nutrient transport, fate and effects. Finally, SCCWRP is facilitating conversations around the uncertainty associated with modeling analyses, with an ultimate goal to help managers optimally use these models to inform coastal nutrient management decisions.