Search

Science activities

Reset filters

3 records


















Records

  • Title

    Effects of drought and elevated nutrients on invasion by Lepidium latifolium and implications for carbon storage in tidal wetlands of the San Francisco Bay- Delta

    Lead Delta Stewardship Council - Delta Science Program
    Description The Delta ecosystem is under threat from multiple concurrent stressors, including drought, nutrient pollution, and invasion by non-native species. Lepidium latifolium is an invasive peren- nial plant that displaces native species and may reduce carbon storage in tidal marshes. Preliminary data suggest that drought may be detrimental to L. latifolium invasion, whereas elevated nutrients may promote invasion. Using experimental manipulation of tidal marsh plots, this project will test the impact of drought and elevated nutrients on the invasion of L. latifolium. The results will inform management of L. latifolium in the Bay Delta by identifying its vulnerabilities to climatic and nutrient conditions, and will be shared with management agencies including East Bay Regional Parks, San Pablo Bay National Wildlife Refuge, and Palo Alto Baylands, among others. The results will also be integrated with the PI’s dissertation research on the carbon storage capacity of L. latifolium, in order to inform wetland carbon offset policies.
    Science topics None specified
    Updated December 21, 2023
  • Title

    Large and small-scale sediment dynamics during (after) the drought

    Lead Delta Stewardship Council - Delta Science Program
    Description Turbidity plays a key role in Delta aquatic ecosystems, where suspended sediment can limit light for phytoplankton growth, transport contaminants, provide protection from predation for many fish species, and contribute to natural sediment recovery in shallow water habitats. The impact of drought conditions on water quality and ecological health is not well studied in estuarine systems, and more information is needed to manage the impacts of California’s drought and recovery in the Delta. This project will examine the effects of drought conditions on turbidity, particularly the interplay between estuarine turbulence, suspended sediment flocculation (particle aggregation), and in-water light levels. Information from this project will contribute fundamental knowledge on flocculation dynamics, help identify critical points for turbidity control during drought, and improve modeling and predictions of sediment transport within the Delta.
    Science topics None specified
    Updated January 4, 2024
  • Title

    The Relative Contributions of Contaminants to Ecological Risk in the Upper San Francisco Estuary

    Lead Delta Stewardship Council - Delta Science Program
    Description This project developed methods to calculate risk of mixtures of pesticides for the Upper San Francisco Estuary (USFE). We used curve fitting to estimate the exposure-response curves for each individual chemical and then the mixture. For the mixtures, the models were normalized for specific ECx values. In that way, the curve fitting was optimized for effects that are comparable to most threshold values. A Bayesian network was built that incorporated five different pesticides and mercury. The input distributions of the contaminants were measured amounts from each of the six risk regions. We also explored three different methods of combining the results of the three pathways – additive, average, and expert judgement. The initial result was the BN model’s Predicted Fish Mortality (%). The Sensitivity analysis (mutual information) identified the most important components of the Bayesian network in determining the toxicity. The top two pathways were the Malathion/Diazinon Mortality pathway and the Mercury Mortality pathway. For the individual nodes Mercury, Bifenthrin and Season were key. Currently, we are completing the risk assessment network by adding Chinook salmon and Delta smelt population pathways to estimate risk to the six Risk Regions. A major accomplishment was the demonstration that curve fitting using additive models for mixtures can be used to estimate fish toxicity in this proof-of-concept model. Bifenthrin, the specific risk region, and season were the inputs that were most important to the calculation. Factors determining macroinvertebrate community structure were identified using multivariate tools. Water quality parameters were the most important in determining clusters of similar macrobenthic communities. Because contaminants were not statistically significant in determining these patterns, further analysis of macroinvertebrate community structure was postponed. At this time, the techniques applied in this program appear applicable to estimating risk due to the variety of chemicals and other stressors to the multiple endpoints under management in the USFE.
    Science topics None specified
    Updated January 24, 2024