This project will evaluate sublethal toxicity of current-use and new fire retardants on Chinook Salmon, a listed species, as well as Rainbow Trout. Non-weathered and weathered retardants will be tested, with the intention being to generate standard LC50s and EC50s from embryo to alevin, and for weathered retardants to more closely mimic exposure a first flush-like event. Behavioral alterations, yolk sac size and potential latent effects on growth will be recorded. These data will allow managers to design approaches for fire management and prevention that have the lowest possible impact on waterways.
Pesticide mixtures originating from both legacy and current-use chemicals are widely detected in Delta waters, sediments, and invertebrate prey, posing potential risks to juvenile Chinook Salmon during critical rearing periods. While pesticides have been measured in juvenile salmon and their prey, substantial uncertainty remains regarding how mixtures of contaminants affect fish behavior and physiology, and how these effects vary across space and time within the Delta. This science activity will apply a recently developed response spectrum modeling framework to evaluate spatial and temporal patterns of sublethal pesticide effects on juvenile Chinook Salmon rearing in the Delta. The model integrates pesticide concentrations measured in salmon tissues to predict behavioral and physiological impairment associated with complex pesticide mixtures. Juvenile fall-run Chinook Salmon collected through existing Delta monitoring programs, including archived specimens from prior years, will be analyzed alongside hatchery-origin juveniles deployed in cages at multiple Delta locations. This combined approach will allow assessment of how pesticide bioaccumulation and model-predicted effects vary across habitats, seasons, and hydrologic conditions. Results will provide a predictive assessment of where and when pesticide mixtures are most likely to impair juvenile salmon performance, with implications for growth, survival, and population-level outcomes. The activity will support management decisions related to pesticide regulation, TMDL development, and evaluation of habitat restoration actions, including reconnected floodplain rearing habitats. In addition, spatial patterns of pesticide bioaccumulation may help identify contaminant sources and inform targeted remediation strategies.
Cyanobacteria are the most common plankton causing harmful algal blooms in freshwater. The variety of cyanotoxins produced by cyanobacteria can impact the nervous system, liver, gastrointestinal tract, respiratory system, and skin of humans and other animals. In the Sacramento-San Joaquin Delta (Delta), cyanobacterial harmful algal blooms (cyanoHABs) have become more prevalent since the late 1990s. Even with the welldocumented occurrence of cyanoHABs in the Delta over the last 15 years, there is no consistent monitoring program in the region, making it challenging to identify management actions to mitigate their occurrence and effects.
To fill this knowledge gap, this project focused on measuring cyanotoxins and cyanoHABs in the Delta, organizing relevant data for stakeholders, and synthesizing data about cyanoHAB extent and drivers. In addition to the generation of new data, this project developed tools to integrate existing and future data collection efforts. Synthesis of these data will help assess the status and trends of cyanoHABs in the Delta, elucidate factors contributing to bloom formation, cyanotoxin production, and transport, and ultimately better understand the effects of cyanoHABs on humans, other animals, and the ecosystem.
