Mercury Strategy Outline RMP CFWG September 14, 2007

CalFed Bay-Delta Mercury Strategy Core Components 1. Quantification and evaluation of mercury and methylmercury sources 2. Remediation of mercury source areas 3. Quantification of effects of ecosystem restoration on methylmercury exposure 4. Monitoring of mercury in fish, health-risk assessment, and risk communication 5. Assessment of ecological risk 6. Identification and testing of potential management approaches for reducing methylmercury contamination

Mercury Management Questions (Delta Tribs Mercury Council) 1. What is the nature and extent of the human health and ecological risks caused by mercury in the Sacramento River Watershed and downstream waters? 2. How well understood is the nature of mercury risk and the ability to reduce it? 3. What is a prudent course of action to reduce mercury risk in the SRW?

Delta Tribs Mercury Council Knowledge Gaps RMP likely to encounter similar gaps Sources- loads from air, native soils, hot springs, mine tailings, bioavailability of diff source types Transport/transformation- water quality effects on MeHg loads, uptake from various tribs, locations Hg exposure various locations- food chain relationships, human consumption Risk for given exposures- demonstrated effects of mercury in humans and wildlife

RMP Mercury Management Questions 1. Where is mercury entering the food web? 2. Which sources, processes, and pathways contribute disproportionately to food web accumulation? 3. Can we do anything about these high-leverage processes, sources, and pathways? 4. What effects can be expected from management actions? 5. Will total mercury reductions result in reduced food web accumulation?

Where is mercury entering the food web? Spatial and temporal dimensions to the question – General vs hotspot priority (target species, random vs fixed site) – Much of Bay above targets – Food web accumulation hotspots – Methylation hotspots

Which sources, processes, and pathways contribute disproportionately to food web accumulation? Sources- is all Hg ultimately bioavailable (for methylation, uptake)? Processes- what (co)factors affect transport, transformation, uptake (what spatial and temporal scales of interest)? Bioaccumulation- biggest jumps at lowest trophic levels (primary producer)

Can we do anything about these high- leverage sources, processes, and pathways? Sources- Reduce totHg? Selected reactive souces? Processes- Adjust (co)factors (aeration, flushing, nutrient loading) Bioaccumulation- choose species, habitat design? (likely least flexibility?)

What effects can be expected from management actions? Implies need to model questions 1 – 3? – Possible with conceptual or semi-quant models? Interpret monitoring data? – Pre- post- action – Appropriate spatial and temporal scales (with associated variability)

Will total mercury reductions result in reduced food web accumulation? Currently tot Hg reductions the largest component of management strategy A form of MQ 2 (which sources.. contribute to…) Experimental or field approaches may be valuable

How to prioritize? RMP Qs 2, 3, currently least known Large factors, large uncertainties first – Portion of Hg convertible to MeHg – MeHg sources- in situ production, sed-water exchange, tributary loads, – Loss pathways- degradation, export MeHg mass budget tool to ID gaps – Illustrating sensitivity to uncertainties