# Presentation: 095795

## Mercury in Aquatic Ecosystems

- Celeste Journey

- U.S. Department of the Interior
- U.S. Geological Survey
- South Carolina Water Science Center

**Notes:**
Title

## Contributors to Presentation

- USGS National Mercury Team
- NAWQA Mercury Topical Study
- Mark Brigham
- Wisconsin Water Science Center Mercury Laboratory
- David Krabbenhoft
- _[http://infotrek.er.usgs.gov/mercury/](http://infotrek.er.usgs.gov/mercury/)_
- Toxic Substances Hydrology Program
- David Krabbenhoft
- Frank Chapelle and Paul Bradley

- South Carolina Department of Health and Environmental Control
- David Baize
- USGS South Carolina Water Science Center Researchers
- Frank Chapelle, microbial geochemist
- Paul Bradley, microbial geochemist
- Celeste Journey, NAWQA study unit chief

## Detailed mercury studies(USGS-NAWQA study areas)

- Willamette Basin

- Hudson River Basin

- Lake Erie Basin

- Santee Basin

- Georgia-Florida Coastal Plain

- Western Lake Michigan Drainages

- Long Island-New Jersey

**Reference stream**

**Urban stream**

- Detailed mercury studies(USGS-NAWQA study areas)

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

**Mercury**
**“****Axis of Evil”**

## Is Bioaccumulation of Hg in Fish an Issue in South Carolina?

- Are there areas where fish consumption advisories are more prevalent and restrictive?
- Has that changed over time?

## Is Bioaccumulation of Hg in Fish an Issue in South Carolina?

- South Carolina
- State College

- SCDHEC

## Is Bioaccumulation of Hg in Fish an Issue in South Carolina?

- South Carolina
- State College

- SCDHEC

- USGS

## Bioaccumulation in Fish in South Carolina

- Methyl mercury accumulation in fish tissue varies significantly with locality and is a health concern in South Carolina .

- Source:
-  South
- Carolina
- Dept. of
- Health and
- Environ.
- Control
- [units in ppm]

## What drives mercury bioaccumulation in stream ecosystems?

- South Carolina

## What are the significant

- sources and source
- strengths of mercury in
- South Carolina?

## Sources of Mercury

- Point source discharge to water
- Inorganic mercury (Hg+2)
- Atmospheric releases
- Gaseous mercury (Hg0)
- Particulate mercury (PHg)
- Inorganic or reactive mercury (Hg+2)

## Atmospheric Sources of Mercury in South Carolina

- Environmental Working Group: http://www.ewg.org/reports/BrainFood/plants/SC.html
- Compiled from Environmental Protection Agency and Department of Energy data. .

## Mercury Emission By Power Plants in South Carolina:1999

- Environmental Working Group: http://www.ewg.org/reports/BrainFood/plants/SC.html
- Compiled from Environmental Protection Agency and Department of Energy data. .

## Mercury Sources in Southeast Region

- Environmental Working Group: http://www.ewg.org/reports/BrainFood/plants/SC.html
- Compiled from Environmental Protection Agency and Department of Energy data. .

## Apparent Effects of Source Strength on Mercury Bioaccumulation

- Estimated atmospheric delivery of Hg to different hydrologic systems throughout the state does not appear to explain fully the variation in mercury levels in fish.

## What drives mercury bioaccumulation in stream ecosystems?

- Atmospheric Deposition
- of Mercury

- Mercury Levels in
- Fish

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

## Mercury Methylation

## Mercury Methylation

**Methylation**

**De-Methylation**

## Numerous influences alter methylation...

- New impoundments (reservoirs, wetlands)
- Cycles of wetting and drying
- Sulfur recycling
- Sulfate loading
- Temperature
- Redox condition

**Notes:**
Virtually every study that has examined mercury in any aquatic ecosystem component—from water to fish—has  found that... methylmercury production or bioaccumulation is exacerbated by:
Creating new permanent impoundments, and/or
Repeated cycles of wetting and drying.

## Redox Zones

**Dominant Microbial**
**Community**

**Dominant Redox **
**Process**

- Oxidizing

- Reducing

## What are the right conditions?

- Low-alkalinity (low pH) and humic (organic carbon enriched) lakes or ponded areas
- Lowland areas subjected to prolonged inundation
- Darkwater and dilute coastal streams
- Flooded areas (e.g., newly formed reservoirs)
- Wetlands and wetland-influenced waters
- Still more to learn...
- Saltwater environments versus freshwater
- Sulfate and DOC interactions
- Other influences?

## Goldilocks Concept

- Sulfate/sulfide relation to methylation
- “Too Hot” Zone:  too much sulfide
- Inhibits methylation
- “Too Cold” Zone: not enough sulfate
- Limits methylation
- “Just Right” or Goldilocks Zone – everything is just right!
- Methylation process over-rides the demethylation process
- Accumulation of methylation occurs

## Methylation Efficiency

- Total Mercury in Sediment and Water =>
- Delivered to system from atmosphere or point source discharge
- Includes inorganic and methylated forms
- Net Methylmercury in sediment and water
- Final product of both methylation and demethylation processes
- Represents what is available for accumulation in aquatic biota
- Ratio of these two is called methylation efficiency
- Methylmercury concentration to Total mercury concentration

## Methylation Efficiency

- For example:
- Basin A is a highly contaminated basin with total mercury in the sediment of 1000 ng/g and methylmercury of 20 ng/L.
- Methylation efficiency = 0.02
- Basin B has a low mercury load of total mercury in sediment of 100 ng/g and methylmercury of 8 ng/L.
- Methylation efficiency = 0.08

## Methylation Efficiency

- USGS National Pilot study identified relatively high methylation efficiency in the sediment and water associated with high levels of Hg in fish tissue in the Edisto River basin.
- Krabbenhoft, D.P., Wiener, J.G., Brumbaugh, J.G., Olson, W.G., DeWild, M.L., and Sabin, T.J., 1999, A national pilot study of mercury contamination of aquatic ecosystems along multiple gradients; in, Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substance Hydrology Program Conference in Charleston, SC:  U.S. Geological Survey Water-Resources Investigations Report  99-4018-B, p.147-160.

## What drives mercury bioaccumulation in stream ecosystems?

- What drives mercury bioaccumulation in stream ecosystems?

## Food web  -How manyTrophic Levels?

**Biomagnifies**

## NAWQA Mercury Topical and Synoptic Study Site

- Edisto River near Givhans Ferry State Park (USGS station number 02175000)
- Old NASQAN Site
- NAWQA Trend Site

## Mercury Deposition Network

## Slide 34

## Slide 35

## Slide 36

## Sediment Microbial Community Study:  USGS Toxic Substance Hydrology Program

- The ability of indigenous microbial populations to perform _net_ mercury methylation varies spatially and with depth in **aquatic sediments.**

## Methylation ratio(methyl Hg/total Hg in sediment)

## Microbial Ecology Using Quantitative PCR

## These Results Suggest:

- Methylation ratio increases downstream in the Edisto River Basin.
- Methylation potential varies areally and vertically in Edisto River Basin sediments.
- Methylation potential appears to be related to organic carbon content and microbial ecology.

## What forest management practices may affect mercury processes?

- Prescribed burns
- Soil erosion
- Land development

## In aquatic ecosystems, mercury runoff may be...

- _Increased_ by:
- Erosion & weathering of soils
- Low-intensity fires?
- Urbanization & increase in impervious surfaces
- Increased inputs
- _Decreased_ by:
- Soil restorative processes
- Intense fires
- Decreased inputs

## Notes related to previous slide, including selected references [page 1 of 2]

- Soil erosion and increased Hg runoff:
- (See: Balogh et al., 1997, Environ. Sci. Technol., v 31, p. 198; Balogh et al., 1998, Environ. Sci. Technol., v 32, p. 456; Balogh et al., 2000, J. Environ. Qual., v 29, p. 871).
- Fires and mercury runoff:  The effect of fires is likely complex, temporally dynamic, and likely depends on more environmental variables than can be summarized herein.  Fire likely affects  both mercury speciation and total mercury concentration in runoff. Low-intensity fires may promote runoff of higher methylmercury concentrations (see: Amirbahman et al., 2004, Water, Air, & Soil Pollut., v 152, p. 313), possibly due to enhanced methylation.  Hotter fires volatilize mercury (Sigler et al., 2003, Environ. Sci. Technol., v 37, p. 4343; Cannon W.F. et al., 2002, Geological Society of America Annual Meeting, Oct. 22-27, 2002, http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_40419.htm), and may affect mercury bioaccumulation (Garcia & Carignan, 1999, Can. J. Fish. Aquat. Sciences, v 56, p. 339).  More research is needed to describe the role of fire on mercury runoff and speciation.

## Notes related to previous slide, including selected references [page 2 of 2]

- Mercury runoff and urbanization (See: Mason and Sullivan, 1998, Water Resources, v 32, p. 321-330)
- Mercury runoff and soil restorative processes: This argument is the converse of the above notes on erosion processes that exacerbate mercury runoff.  Soil erosion increases mercury runoff to aquatic ecosystems; controlling erosion in a highly erodible setting would tend to decrease mercury runoff.  Also, soil organic carbon holds a large reservoir of mercury at the earth’s surface.  Mineralization of this soil organic matter is exacerbated with many land use and intensive cultivation practices, implying potential for release and runoff of soil-bound mercury. Conversely, conservation-minded land use and cultivation practices can restore soil organic matter (Tilman, Nature 1998, v 396, p. 211), implying potential for retention of atmospherically deposited mercury on the land surface.

## Start simple...

- Intensive study area

- Modified from Reed Harris, Tetra Tech Inc.

- River mercury studies & model development—

## Build complexity over time...

- Intensive study area

- Modified from Reed Harris, Tetra Tech Inc.

- River mercury studies & model development—

## Summary

- USGS is studying methylmercury in key components of stream ecosystems, at selected sites across the nation.
- Several temporal and spatial scales
- Detailed studies that include monitoring mercury and methylmercury in the water, sediment, pore water, and food web (algae, benthic invertebrates, forage fish, and top predator fish).
- Spatial (synoptic) assessments
- Sediment microbial studies