2018-2019 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 also can lead to low dissolved-oxygen levels that can trigger declines in fishery harvests and in diversity of aquatic life. However, determining the nutrient load a water body can assimilate is challenging because, unlike with contaminants, some level of nutrient input is necessary to sustain life. Consequently, environmental managers must work to control the deleterious impacts of excessive nutrients and other waterbody conditions that can exacerbate eutrophication. SCCWRP has been at the forefront of eutrophication research efforts in both freshwater and coastal-ocean systems, working to build a foundational body of science for diagnosing eutrophication, identifying appropriate nutrient targets for California’s water bodies, and tracking where nutrients are coming from and what is happening to them. 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 (nutrients) and biointegrity policy to protect all of California’s wadeable streams, lakes and estuaries. 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.
While the symptoms of eutrophication vary by water body type, the conceptual approach to developing tools to diagnose eutrophication and identify nutrient targets is similar for all water bodies. The first step is to build consensus around a conceptual model that identifies symptoms of eutrophication (e.g., altered dissolved oxygen concentrations, increased algal abundance) and their link to both nutrient loads and other contributing water body factors. The second step is to design a framework for assessing the condition of a water body, one that focuses on eutrophication symptoms instead of nutrients themselves. An important element of this framework is to identify thresholds for each symptom that equate to protection of human and ecosystem values and avoidance of adverse impacts. The third step is to build statistical and mechanistic models that link eutrophication symptoms to nutrients and other factors, such as habitat and hydromodification, to examine environmental-management scenarios that might prevent an ecosystem impact. An important element of mechanistic model development is conducting process studies that document the fate of nutrients as they are cycled through an aquatic habitat. The final step is to assist in transferring this technology to environmental managers.
This year, SCCWRP will continue its work to incrementally build a knowledge base and technical foundation that will allow nutrient inputs to be more effectively monitored and managed in California, both in fresh and marine waters. SCCWRP’s focus for 2018-19 will be on:
- Building the technical foundation for nutrient targets in California water bodies: SCCWRP is pursuing a multi-pronged approach toward building the technical foundation upon which policy decisions regarding biointegrity, nutrient and eutrophication targets for California’s wadeable streams, lakes and estuaries will be based:
- SCCWRP is developing an Algal Stream Condition Index (ASCI) to support biointegrity assessments and to link algal and benthic macroinvertebrate community composition to pathways of eutrophication impacts.
- SCCWRP is using the consensus of wadeable stream experts to calibrate the range of scores for ASCI and the benthic macroinvertebrate-based California Stream Condition Index (CSCI) that correspond to levels of ecological condition and function, from high to low. This information will support decisions regarding biological goals for CSCI and ASCI by helping to relate these targets back to levels of beneficial-use protection.
- SCCWRP is working toward development of statistical models that relate standardized stream bioassessment indices to nutrient concentrations and eutrophication indicators. Such models may provide the approach used by the statewide biostimulatory/biointegrity policy on how to make decisions on nutrient targets.
- SCCWRP is continuing to demonstrate how science can inform a combined biostimulatory/biointegrity approach to watershed management. Through the Santa Margarita River Nutrient Management Initiative, SCCWRP is supporting stakeholders by collecting monitoring data and developing statistical and mechanistic process models to establish watershed-specific nutrient targets for the Santa Margarita River’s estuary and main stem, based on biointegrity goals.
- Assessments of harmful algal blooms (HABs): To understand the magnitude and spatial extent of harmful algal blooms across marine, estuarine and fresh water systems, SCCWRP is studying the ecophysiological factors that drive HABs development and proliferation. SCCWRP is focused on: (1) supporting partners to pinpoint which HAB organisms are present and which toxins are being produced to better characterize the extent of the problem, including through DNA barcoding, which is being coupled with rigorous analyses of toxin presence to more fundamentally characterize lakes, streams and estuaries, (2) conducting studies to understand the drivers for HABs proliferation and toxin production, including nutrients, temperature and hydromodification, and (3) supporting the State Water Board’s efforts to develop chlorophyll-a and cyanotoxin targets for lakes, and (4) playing a role in unifying the HABs monitoring and research efforts taking place in freshwater habitats and the coastal zone. To understand the prevalence of cyanobacterial blooms and toxins in California lakes and streams – which can pose a potential threat to human and ecosystem health – SCCWRP is supporting a statewide group that is working to implement a statewide cyanobacteria monitoring strategy.
- Biogeochemical effects of nutrients and carbon in the Southern California Bight: SCCWRP is working with partners to couple biogeochemical models with physical oceanographic models to ascertain the relationship between coastal hypoxia and acidification conditions as sources of land-based nutrient inputs enter the Bight and other locations along the North American West Coast. Management actions, including nutrient load reduction, have been suggested as a strategy for improving local water quality, but the extent of change achieved from nutrient load reductions are uncertain, given that coastal hypoxia and acidification may be driven primarily by climate change and thus operate at a global scale. Coupled biogeochemical and physical circulation models, which don’t exist for near-coastal environments, will be used to evaluate the extent to which anthropogenic nutrients are affecting trends in oxygen and acidification conditions.