Methyl Mercury in Water and Fish Tissue in the Lower Yazoo Basin

Author(s): Myers, K.

Mercury is a leading cause of fish consumption advisories in the United States and is the only metal with a fish consumption advisory in Mississippi. While none of the affected water bodies are within the Mississippi Delta, a 2001 ambient water quality criterion established by the EPA would lower Mississippi’s fish tissue threshold from 1 mg mercury per kg of fish tissue to 0.3 mg methyl mercury per kg of fish tissue. Since studies have shown that nearly 100 percent of the mercury that bioaccumulates in predator fish tissue is methyl mercury, the new fish tissue criterion would become 0.3 mg/kg mercury in fish tissue. The State of Mississippi is expected to implement this new fish tissue mercury criterion within the next year. Implementation will increase the number of water bodies with fish tissue consumption advisories within the State and the Mississippi Delta in particular. Recently the USACE Vicksburg District analyzed the potential for increases in methyl mercury concentrations in surface water and fish tissue based upon completion of the Yazoo Backwater Project’s reforestation component. The analysis used a simplified linear model that compared the potential for changes in methyl mercury production based upon changes in land use, flooded acres, and flood duration. The model predicted that completion of the Yazoo Backwater Project recommended plan and reforestation of up to 55,600 acres of currently farmed agricultural land could have increased methyl mercury production by 3 percent over base conditions. The Vicksburg District’s mercury database includes surface water samples for methyl mercury collected between 2003 and 2008 and mercury in fish tissue samples collected between 1993 and 2008. Surface water samples were collected during flooded conditions in Delta National Forest greentree reservoirs, during flood and non-flood conditions in Delta Nation Forest wetlands, and during summer, non-flood conditions in streams and lakes in the lower Yazoo Backwater Area. The data show that methyl mercury production is highest in areas rich in easily accessible organic matter that undergo extended flooding. Fish tissue mercury concentrations appear to be related to flood duration and the number of acres flooded.


Technical Presentations

  • Delta Water Quality
  • Delta Water and Agriculture
  • Wetlands
  • Water Quality
  • Sediments
  • Non-Point
  • Management and Sustainability
  • Wood Treatment
  • Modeling
  • Soil and Water Treatment


Responsible Site Design: Implementing Innovative Stormwater Management Strategies

The primary goal of the workshop is to create a dynamic learning experience that examines the role of stormwater management in the built environment. The workshop will focus on integrating ecologically sound water management approaches into site design. After the workshop, attendees will be familiar with the following concepts and technical issues:

  • Knowledge of the stormwater treatment chain
  • Knowledge of the impact of land use codes on stormwater management
  • Application of a design process that mitigates the effects of stormwater on-site
  • Knowledge of the relationship between land use codes and design for innovative stormwater management


For information contact:
Jessie Schmidt
Box 9680
Mississippi State, MS 39762