Dr. Jay Davis highlights studies to determine where the greatest potential exists to address methylmercury in the San Francisco Bay
The Regional Monitoring Program (RMP) for the San Francisco Bay is a collaborative partnership between the San Francisco Estuary Institute, the Regional Water Quality Control Board, and the regulated discharger community to provide the scientific foundation to manage water quality and contaminants in the San Francisco Bay. The RMP monitors water quality, sediment quality and bioaccumulation of priority pollutants in fish, bivalves and birds, as well as fund special studies to improve monitoring measurements or the interpretation of data.
In 2003, a strategy for integrated mercury investigations linked to restoration and adaptive management of the San Francisco Bay-Delta ecosystem was developed by a team of independent scientists, with the goal of the strategy being ‘to provide a unifying framework for the integrated investigations needed to build a scientific foundation for ecosystem restoration, environmental planning, and the assessment and eventual reduction of mercury-related risks in the Bay-Delta ecosystem.’
In this presentation, Dr. Jay Davis, senior scientist with the Clean Water Program at the San Francisco Estuary Institute, discusses how the San Francisco Bay Regional Monitoring Program has integrated mercury research and monitoring since 2003, as well as highlighting the progress of other mercury monitoring efforts happening in the Delta and statewide.
Dr. Davis began by saying that the 2003 strategy for mercury put the appropriate focus on biotic exposure to methylmercury with the challenge being to avoid increasing and eventually decrease the exposure. “The bioaccumulation was appropriately referenced in all of the goals, because everything does tie back to that biotic exposure,” he said. “So the focus of this talk is the use of monitoring of mercury in fish as a performance measure to gauge contamination during restoration and in response to other management actions. A secondary theme will be an overview of fish monitoring, what has been done, what is being done, and what is not being done.”
The San Francisco Bay Regional Monitoring Program has been in place since 1993, and is steadily funded at about $3.5 million per year. The program looks broadly at the water quality in San Francisco Bay; mercury is but one of contaminants the program monitors. The overall goal of the program is to collect data and communicate information about water quality in support of management decisions.
“The program is going strong; the funders, the participants, and the regulators are all happy with the program and the reason that they are happy is that we are providing information that helps them make decisions – decisions that are coming up in the near term as well as decisions that they may want to make ten years out or further,” he said. “We have a sharp focus on providing information to support the decision making. The 2003 strategy had a very appropriate emphasis on the linkage to management and helping to inform management.”
“The San Francisco Bay is the one place in California that has a good time series of mercury measurements in fish and sportfish,” he said, presenting a graph showing mercury concentration for striped bass, a key mercury fish indicator for the bay. “It’s the focus of the TMDL, and we have a data set that the RMP has been generating since 1994. There was work done in the early 70s in the very early days on understanding the mercury problem in the estuary. It’s kind of a rare case where we got an early dataset to compare to more recent data, and basically we’ve seen no change. These are size standardized concentrations; the bars are showing median concentrations and the points are showing individual fish, so the median concentrations have been above regulatory thresholds, the level that the state uses.”
After the 2003 strategy was developed, the Regional Monitoring Program focused on mercury for a few years. “We developed strategies for contaminants of particular concern and articulated questions that need to be answered for managing these contaminants, and then implemented a program of studies, and mercury is what got us really going on this. The group that got together to develop this strategy came up with the goal that we adopted for the program to focus on management decisions. For each of these strategies, we developed questions that we want to answer that relate to management decisions, so where and when is mercury entering the food web, what are high leverage processes, sources, and pathways that we should focus our management attention on in order to best reduce the problem.”
“We developed a plan of study and we implemented the plan from 2008 to 2012,” he continued. “One of the keys to success in this program and other efforts that I’ve been involved with is bringing in external advisors like we did with our previous strategy.”
It was a multi-year program of study; one of the elements was beginning to do small fish monitoring. The program had been doing sportfish monitoring but had not done any small fish monitoring, so the program invested about a half million dollars in a three year effort to do some systematic monitoring of mercury in small fish.
Dr. Davis presented a graph of the dataset generated, noting the different years are in different colors. “We covered the system pretty well,” he said. “We showed regional variation with higher concentrations in the southern end of the estuary. There was a lot of seasonal variation. We didn’t see any clear evidence of high leverage pathways that we could direct management to focus on, and we actually found that municipal wastewater effluent appears to be a low leverage pathway, so we can cross one concern off the list.”
The Regional Monitoring Program primarily does monitoring, but does fund research if it’s going to help answer questions that need to be answered. So part of the strategy was a two-year study to look at the effects of legacy mercury in the Bay. The research was able to show a good correlation between the isotope signatures in the small fish and the isotope signatures in the sediment, and so this was an indication of the spatial relationship to the distribution of isotopes in the Bay, he said.
“It clearly pointed towards the New Almaden mining district in the South Bay, and it indicated that the mercury is in our sediment and it is getting into the food chain. That had been kind of a hypothesis before that, but this helped find evidence that it really is getting into the food web.”
The study showed that mercury from historic mining remains a concern; this is not to say that other sources such as urban, industrial, and atmospheric are not also important, but the mining mercury is getting into the food web. “The Bay TMDL has had a total mercury focus, so this was providing support for the approach that they are taking to reduce total mercury inputs,” he said. “It’s not the only thing that the region is pursuing, but it is sort of the cornerstone of the TMDL.”
Another research project was an avian egg project that looked at the effects of mercury and selenium in the eggs of Forster’s terns. There is not a water quality objective for the Bay TMDL, but there is a monitoring target of one-half part per million. The RMP funded researchers to answer the questions is the .5 threshold a reasonable threshold and what are the effects of mercury on Forester’s terns in the Bay.
“The basic conclusion was that the threshold of about .5 parts per million translates to about a 10% reduction in nest success and a lower amount of reduction in the survival of individual eggs and the concentration that we see are way above that, so at least for now, this is a reasonable threshold. We need to drive concentrations down to half part per million, and that’s a big task. When we get there, I think we can fine tune the threshold and see if a more conservative value is appropriate, but it’s pretty protective the way it is, so we sort of felt like we reached a conclusion on the question we were trying to address.”
There was a lot of work that had been done following the 2003 mercury strategy, so one of the last pieces for the Bay’s mercury strategy was a synthesis of the work that had been done in the region. The work was pulled together into a synthesis article that was published in pull the information together in a synthesis article that was published in an environmental research journal. “The focus of the review was whether we can do anything to reduce food web methylmercury in the near term – the next 10 or 20 years. Reducing total mercury is a long-term, maybe century type of time frame effort, but what can we do in the near term.”
In order to answer that question, it’s important to think about the four components of the bay: open bay, tidal marsh, managed pond, and reservoirs, as the species at risk, the biogeochemistry and the options for management vary by habitat, Dr. Davis said. The species of concern differ by habitat: striped bass are the species of concern in the bay; the Ridgway rail in the tidal marsh, Forster’s tern in the managed ponds, and largemouth bass in the reservoirs.
For the open bay, they tried to identify actions that could be done, separating them into elective strategies or conscious actions they could take to affect mercury in the food web and non-elective things that really aren’t under their control.
“Then there are slow knobs and fast knobs, so controlling total mercury inputs is a slow knob, but we were trying to identify any fast knobs that could reduce mercury in the food web in the next 10 or 20 years,” he said. “The only one that we could think of as potential fast knob was nutrient control; there is a big effort underway to evaluate the need for managing nutrient concentrations in the bay and this could affect mercury in the food web. So for the open bay, there’s really not much we can do. The mercury is out into the system, spread throughout the system, and continuing to come into the system from the watersheds, and the response time is going to take many decades.”
Dr. Davis said that for tidal marsh, there is a potential fast knob in looking at the design and placement of the marshes, so it’s an area that deserves further attention. Managed ponds are more highly controlled environments; the hydrology and the placement of the pond can be managed, he noted. For reservoirs, there are several knobs: You can manage the hydrology, you can manage water chemistry, you can manage the fisheries in the reservoirs, and you can basically manipulate biodiultion, he said.
Dr. Davis then presented a summary slide of the knob ratings for the different habitats, noting that for the Regional Monitoring Program, the focus has been on the open water of the bay. It’s debatable among the group whether they should be trying to monitor tidal marsh, and managed ponds are not within the range of what the Regional Monitoring Program looks at.
So they decided to look further into the tidal marsh question, holding a forum in late 2013 where they brought in advisors who came to consensus on several statements:
- Increases most likely in the year or two following restoration; Longer-term monitoring needed to assess the potential increases at later stages.
- Regional increases in biota are far less likely to be detectable than site increases. However, aggregate effect is a concern.
- Support for a regional approach to monitoring, with some sites selected for detailed investigation. Biosentinels needed to track trends and generate hypotheses, and process studies to test hypotheses and gain mechanistic understanding.
- Continued research and pilot studies may identify design features for some sites that minimize methylmercury accumulation in the food web.
Open bay increases are far less likely to be detectable than increases at the site, so for the regional monitoring program, the interest level was reduced, he said, noting that if it were a bigger concern, they would have been more likely to pick up systematic monitoring to look at it.
Another study that the San Francisco Estuary Institute did in partnership with UC Davis outside of the Regional Monitoring Program was the North Bay Biosentinel Project which was funded by the State Coastal Conservancy in two phases at about $200,000 per phase. External advisors were brought in again, and wetland types were compared: managed ponds, breached wetlands, and tidal marsh. “The graphs are showing small fish measurements for a variety of species with the different colors, and one general conclusion is that the breached wetlands are not screaming high with mercury; the highest concentrations in general were in the mature tidal marshes, so that was one encouraging finding that with regard to restoration, we’re not creating a huge mercury hazard.”
Dr. Davis also pointed out that there was a lot of variation among the managed ponds. “I think this helps illustrate how monitoring and research should work together,” he said. “There are some places where the concentrations in the managed ponds are lower, and places where the concentrations are higher, so the monitoring is telling us that, if we can understand why there are these patterns, maybe we can manage the ponds to have more habitats like these with low concentrations.”
He then turned to the Delta. One of the major projects that came out of the first strategy was the fish mercury project which received $4.5 million in funding from CalFed over a 3-year period from 2005-2007. The map shows all the sportfish monitoring locations that were covered; the program covered the Delta and did repeated sampling in the Delta for some stations, but also filled in a big information gap for other parts of the watershed, he said.
Again they had expert advisors guiding them, including experts on risk communication, which was something that was called for in the first strategy. “We had extensive stakeholder involvement and consideration of environmental justice and we had a lot of community-based organizations involved in the project. It was a really cool project and it’s the kind of thing you can do when you’ve got ample funding.”
More recently, a Delta Regional Monitoring Program has taken shape, which just started monitoring last year. Dr. Davis said it’s structured in a similar way to the San Francisco Bay Regional Monitoring Program in terms of funding and governance, but the funds just started to flow last year, and there are limited funds in this initial startup mode. The group has identified priorities to be pesticides, pathogens, nutrients, and mercury, with mercury at the bottom of the list of four, he said.
“The program has developed a mercury plan including several of the investigators here helping us come up with a plan for monitoring mercury in sportfish and water with limited resources that we expect to be available,” he said. “The map is showing that we’ve got about 10 sites for fish that we identified and five sites for water, but there are no funds yet for implementing this plan. We applied for funding from Prop 1 and just found out that we did not get that funding, so where we go from here is unclear. We may try again with Prop 1 later in the year, but the plan is developed but not yet funded.”
Dr. Davis said that significant work has been done on statewide monitoring by the Surface Water Ambient Monitoring Program (SWAMP). From 2007 to 2011, a thorough sampling of mercury and other contaminants in sportfish was conducted throughout the state, including lakes and reservoirs, rivers and streams, and the coast.
“We generated a really great data set in this period and one interesting finding was … we saw mercury accumulation to levels of concern wherever we looked, whether we were in a historic mining area or whether there was geologic mercury in the bedrock or not. We found anywhere we sampled long-lived predator species, we saw mercury levels of concern; there were some places that had low concentrations, but they were pretty rare.”
“This work has helped spur the statewide mercury control program, the statewide team for reservoirs, and the development of statewide mercury water quality objectives,” he said. “Also consumption advisories have been developed; there is now a statewide advisory for reservoirs. For the reservoirs who don’t have their own specific advice, there’s a general advisory. There have been a lot of specific advisories that were generated largely by the fish mercury project but also just by these other datasets that have been generated.”
Dr. Davis said that also among the work being done statewide, there is now the beginning of a trend monitoring program. “The first blitz of work was a status assessment but for the approximately 190 lakes where we get largemouth bass in the water bodies, they are a priority. We now have a sampling schedule for sampling each of these lakes on a ten year cycle. We are using a kind of rotating panel design that’s got randomization in it, so each time we go out, we’ll be getting a representative statewide average, so over this ten year period and beyond, we will finally have a dataset besides San Francisco Bay that will help us understand whether there is a regional or statewide trend in mercury concentrations in our food webs.”
With respect to information needs, Dr. Davis said although great work has been done, there isn’t any additional monitoring beyond what they had back in 2003. “We have the Bay Regional Monitoring Program. We’re about to implement a plan for the Delta, but there’s really no significant new monitoring in place.”
Dr. Davis then concluded with his thoughts on the next steps. “We should obviously continue the Regional Monitoring Program … I think a gap for the Bay is the marsh monitoring. I think there is a need for better coordination of marsh monitoring and process studies; there are projects that are occurring like the North Bay Biosentinel, a lot of work in the south Bay salt ponds, I’m not fully aware of all the work that is being done, but I think there could be some synergy gained by coordinating that work and one way to achieve coordination would be this external peer review route that has been so successful and helpful in all the other programs I’ve been involved with.”
Dr. Davis noted that there’s potential with the managed ponds. “The Forster’s terns are largely foraging in managed ponds, and managed ponds are environments that we can control, so we might be able to actually reduce Forster’s tern exposure and risk. If the regulatory agencies decide to take that on, so if that happens, they will need good science to support it.”
“Then for the Delta, we need to implement that plan we’ve developed for sportfish and water,” he said. “I think there is a similar need for monitoring these specific restoration projects and management actions with a systematic approach that includes local and regional monitoring, biosentinel supported by research studies.”
FOR MORE INFORMATION …
- For more information on mercury and methylmercury management, click here.
- For more information on the mercury workshop, click here.
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