Conceptual Foundations for Modeling Bioaccumulation in San Francisco Bay RMP Technical Report by Aroon R. Melwani Ben K. Greenfield Donald Yee Jay A.Davis CONTRIBUTION NO. 676 SAN FRANCISCO ESTUARY INSTITUTE 4911 Central Avenue, Richmond, CA 94804 AUGUST p: 510-746-7334 (SFEI), f: 510-746-7300, 2012 www.sfei.org This report should be cited as: Melwani, A.R., Greenfield, B.K., Yee, D. and Davis, J.A. (2012). Conceptual Foundations for Modeling Bioaccumulation in San Francisco Bay. RMP Technical Report. Contribution No. 676. San Francisco Estuary Institute, Richmond, California. Conceptual Foundations for Modeling Bioaccumulation in San Francisco Bay Regional Monitoring Program Technical Report A.R. Melwani, B.K. Greenfield, D. Yee, and J.A. Davis San Francisco Estuary Institute SFEI Contribution # 676 Suggested Citation: Melwani, A.R., B.K. Greenfield, D. Yee, and J.A. Davis. 2012. Conceptual Foundations for Modeling Bioaccumulation in San Francisco Bay. SFEI Contribution # 676. San Francisco Estuary Institute, Richmond, CA. Final Report Table of Contents EXECUTIVE SUMMARY ______________________________________________ 4 1. Introduction________________________________________________________ 7 2. Target Chemicals: Bioaccumulation Processes and Biota Concentrations________ 8 Methylmercury _______________________________________________________ 9 Selenium ___________________________________________________________ 12 Polychlorinated Biphenyls (PCBs) _______________________________________ 13 Polybrominated Diphenyl Ethers (PBDEs) ________________________________ 16 Dioxins ____________________________________________________________ 17 Organochlorine Pesticides (DDTs, Chlordanes, Dieldrin) _____________________ 18 Perfluorinated Compounds (PFCs)_______________________________________ 19 3. San Francisco Bay Indicator Species of Concern__________________________ 19 Striped Bass ________________________________________________________ 20 White Sturgeon ______________________________________________________ 21 Jacksmelt___________________________________________________________ 21 Mississippi Silverside _________________________________________________ 22 California Least Tern _________________________________________________ 23 Forster’s Tern _______________________________________________________ 23 California Clapper Rail________________________________________________ 24 Song Sparrow _______________________________________________________ 25 Longjaw Mudsucker __________________________________________________ 25 White Croaker_______________________________________________________ 26 Shiner Surfperch _____________________________________________________ 26 Topsmelt ___________________________________________________________ 27 California Halibut ____________________________________________________ 28 Double-crested Cormorant _____________________________________________ 29 California Mussel ____________________________________________________ 30 Harbor Seal _________________________________________________________ 30 4. Key Concepts Supporting Bioaccumulation Modeling _____________________ 31 Factors Influencing Bioaccumulation _____________________________________ 31 Distribution of Contaminants ___________________________________________ 31 Management Actions _________________________________________________ 33 Seasonal Trends _____________________________________________________ 34 Long-term Trends ____________________________________________________ 35 Habitat Types _______________________________________________________ 36 Open Waters ______________________________________________________ 36 Sloughs, Channels, and Mudflats ______________________________________ 36 Salt Ponds ________________________________________________________ 37 Tidal Marsh_______________________________________________________ 37 Summary of Habitat Issues and Previous Model Development _______________ 37 Spatial Scale and Movement____________________________________________ 38 Home Range ______________________________________________________ 39 Methods to Quantify Home Range Scale and Biota Movement_______________ 40 Uptake into the Bay Food Web __________________________________________ 42 Mechanisms of Contaminant Uptake and Elimination _______________________ 43 2 Final Report Dietary Uptake ______________________________________________________ 44 Elimination Processes _________________________________________________ 44 Growth ____________________________________________________________ 45 Ecological Attributes _________________________________________________ 46 Life History, Dietary Mode and Trophic Position _________________________ 46 Benthic Versus Pelagic Habitat _______________________________________ 47 Lipid Content _____________________________________________________ 49 Age, Body Size, and Sex_____________________________________________ 50 Abiotic Covariates ___________________________________________________ 51 Bioavailability_____________________________________________________ 51 Total Organic Carbon (TOC) _________________________________________ 52 Redox Potential____________________________________________________ 52 5. Summary and Recommendations ______________________________________ 53 6. Acknowledgements_________________________________________________ 56 7. References________________________________________________________ 56 8. Tables ___________________________________________________________ 77 9. Figures___________________________________________________________ 79 3 Final Report EXECUTIVE SUMMARY Bioaccumulation of contaminants is a significant water quality concern in San Francisco Bay. The Bay is included on the 303(d) list due to elevated concentrations of many contaminants (e.g., PCBs, mercury, and DDTs) present in sport fish, bird eggs, and small fish species. Mechanistic bioaccumulation models can be valuable tools to support management of bioaccumulative contaminants. A food web bioaccumulation model for San Francisco Bay has been developed and validated for PCBs and organochlorine pesticides. However, this model has yet to be parameterized at the sub-embayment or site-specific scale, and has not been explicitly developed to make time-dependent predictions. Mechanistic models of bioaccumulation have not been developed for other pollutants of concern, such as methylmercury or dioxins. In addition, the modeling and monitoring performed to date have not provided quantitative mechanistic links between particular sources (e.g., contaminated sites and tributary loadings on the margins of the Bay) and local and Bay- wide contaminant concentrations in key target species. Also, the models developed to date have limited capacity to forecast the impact of localized management actions on contaminant concentrations and associated risks for wildlife and humans. Since these model capabilities could be of great value in choosing management actions, there is a need to adapt the modeling approach to develop a better description of the relationship between contaminants in the margins and bioaccumulation in biota on local and regional scales. The objectives of this report are to summarize key datasets and current knowledge of bioaccumulation in the Bay, and to identify priorities for future monitoring and modeling to support management of bioaccumulative pollutants. The report is intended for a technical audience of water quality managers, stakeholders, and external peer reviewers responsible for guiding the RMP modeling strategy and modeling tools utilized in San Francisco Bay. This report summarizes empirical information on bioaccumulation in the Bay, with a focus on support for development of bioaccumulation models. A review of information on the pollutants of greatest concern in the Bay (methylmercury, PCBs, selenium, dioxins, organochlorine pesticides, PBDEs, and PFCs) is presented in Section 2. Key attributes of the primary indicator species are reviewed in Section 3; these are critical in understanding the information they provide on bioaccumulation and in building models to predict how concentrations in their tissues will respond to management actions. Section 4 provides a discussion of key concepts related to bioaccumulation modeling and highlights priority information gaps. The report provides a conceptual foundation for a path forward for RMP studies of bioaccumulation, including modeling and monitoring, in support of effective and efficient efforts to reduce concentrations of contaminants in the Bay food web. RMP fate models must be developed with a sharp focus on understanding and predicting bioaccumulation. 4 Final Report Models of fate in water and sediment must be efficiently coupled with bioaccumulation modeling. A conceptual understanding of the patterns revealed in food web monitoring to date provides a foundation for future modeling efforts. The following highlights of these patterns have a major bearing on consideration of the next steps in bioaccumulation studies. Long-term monitoring of sport fish has indicated no trend in MeHg concentrations since the early 1970s and no trend in concentrations of PCBs and other organics since 1994. In contrast to the sport fish, concentrations of organics have declined significantly in bivalves in the open Bay based on time series covering 1980 to the present. MeHg in the food web varies spatially 1) at a regional scale, with highest concentrations in the South Bay, and 2) with additional finer-scale variation at a local scale that is not clearly associated with source