Eutrophication Research Plan

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

2021-2022 Executive Summary

Excess nutrients introduced to aquatic habitats through human activity (i.e., nitrogen and phosphorus) – combined with other changes such as modifications to hydrology, temperature and light – 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 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 man-made toxic contaminants, some level of nutrient input is necessary to sustain life. Consequently, environmental managers must balance the need to maintain nutrients that support aquatic life with the need to control the deleterious impacts of excessive nutrients and other water body conditions that can exacerbate eutrophication. SCCWRP is working to quantify how much nutrients in a given water body is too much, and how nutrients combine with other environmental factors to trigger eutrophication. SCCWRP’s long-term goal is to develop comprehensive eutrophication management strategies, including the ability to pinpoint when and where eutrophication is likely to occur, how to prevent it, and how to mitigate it.

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 (i.e., aquatic life) policy to protect California’s wadeable streams, lakes and estuaries. SCCWRP is also supporting the Water Boards’ recently developed Freshwater Harmful Algal Blooms (HABs) Program in developing cost-effective methodologies to monitor HABs and their linkage to eutrophication. 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 HABs and declines in dissolved oxygen and pH. Across all of this work, SCCWRP is focused on: (1) Building consensus around conceptual models that identify symptoms of eutrophication (e.g., altered dissolved oxygen concentrations, increased algal abundance, acidification, toxic HABs) and their link to both nutrient loading and other contributing water body factors; (2) designing frameworks for assessing water body condition and identifying thresholds for specific symptoms that will protect human and ecosystem values while avoiding adverse impacts; (3) developing cost-effective monitoring and assessment strategies (4) building statistical and mechanistic numerical models that link eutrophication symptoms to nutrients and other factors, such as habitat and hydromodification, to examine environmental management scenarios that prevent an ecosystem impact; and (5) assisting in transferring new tools and strategies to environmental managers.

This year, SCCWRP research will continue building a knowledge base that allows HABs and eutrophication to be more effectively monitored and managed in California, both in fresh and marine waters. SCCWRP’s focus for 2021-22 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 ongoing 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. This year, SCCWRP will continue its focus on: (1) supporting the State in launching a comprehensive inland Freshwater HABs Program monitoring and assessment strategy, 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.