Groundwater discharge zones are important spawning areas for fish because they provide a thermally stable habitat. Research at three streams in the Chesapeake Bay Watershed with areas of focused groundwater discharge revealed that groundwater also is a source of phytoestrogens and herbicides that could result in fish exposure during sensitive life stages.
In the Chesapeake Bay Watershed, smallmouth bass (Micropterus dolomieu) populations have shown signs of infectious disease and endocrine disruption. Exposure to contaminants during sensitive life stages can have a negative effect on fish health; therefore, understanding groundwater discharge as a contaminant exposure pathway for nesting smallmouth bass is of great interest to stakeholders in the Chesapeake Bay Watershed. However, little work has focused on understanding the role of groundwater discharge zones as source of contaminants to streams.
To fill this gap, scientists used recently refined heat tracing methods to identify and quantify groundwater discharge zones in three streams in the Chesapeake Bay Watershed near smallmouth bass spawning areas. Paired groundwater and water samples from these three streams were analyzed for phytoestrogens (natural estrogens that occur in plants), herbicides (such as atrazine) and their breakdown products (such as hydroxyatrazine), steroid hormones, sterols (such as cholesterol) and bisphenol A. Chemicals detected in groundwater discharge zones were compared to those in the paired stream samples to better characterize the contribution of groundwater discharge as a contaminant source in the studied streams.
An important finding of this research was that phytoestrogens and herbicides were present in the streams and the corresponding groundwater discharge zones, with concentrations generally lower in the groundwater samples. The most frequently detected chemicals in this study were cholesterol (88 percent, fecal sterol), genistein (79 percent, phytoestrogen), atrazine (74 percent, herbicide), formononetin (55 percent, phytoestrogen), and metolachlor (50 percent, herbicide).
Lower contaminant concentrations in groundwater discharge compared to those in adjacent streams indicate that runoff events are likely the largest episodic contributors of contaminant concentrations at the streams sampled, but groundwater discharge zones appear to be a consistent contributor of contaminants such as pesticides and phytoestrogens. Thus, these groundwater discharge zones represent a focused chemical exposure pathway in a habitat used by aquatic organisms during sensitive life stages, such as spawning. Although not quantified in this study, exposure of organisms to contaminants by way of groundwater discharge during sensitive early life stages could have harmful sublethal effects on growth, development, and reproduction with time.
This research was supported by the U.S. Geological Survey's Chesapeake Bay Priority Ecosystems and Fisheries programs, and the U.S. Geological Survey Ecosystems Mission Area’s Environmental Health Program (Contaminants Biology and the Toxic Substances Hydrology).
See below for other science related to this research.
Thompson, T.J., Briggs, M.A., Phillips, P.J., Blazer, V.S., Smalling, K.L., Kolpin, D.W., Wager, T. 2021. Groundwater discharges as a source of phytoestrogens and other agriculturally derived contaminants to streams. Science of the Total Environment, v. 755.
Drinking Water and Wastewater Infrastructure Science Team
Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
New Virus Identified in Melanistic Skin Lesions on Smallmouth Bass from the Chesapeake Bay Watershed
Long-term Studies Examine Contaminant Exposure and Reproduction of Ospreys Nesting in Two Large United States Estuaries
Food Resources Lifecycle Integrated Science Team
- Overview
Groundwater discharge zones are important spawning areas for fish because they provide a thermally stable habitat. Research at three streams in the Chesapeake Bay Watershed with areas of focused groundwater discharge revealed that groundwater also is a source of phytoestrogens and herbicides that could result in fish exposure during sensitive life stages.
Sources/Usage: Public Domain.A curious smallmouth bass following behind scuba divers in Sparkling Lake, Vilas County, Wis. In the Chesapeake Bay Watershed, smallmouth bass (Micropterus dolomieu) populations have shown signs of infectious disease and endocrine disruption. Exposure to contaminants during sensitive life stages can have a negative effect on fish health; therefore, understanding groundwater discharge as a contaminant exposure pathway for nesting smallmouth bass is of great interest to stakeholders in the Chesapeake Bay Watershed. However, little work has focused on understanding the role of groundwater discharge zones as source of contaminants to streams.
To fill this gap, scientists used recently refined heat tracing methods to identify and quantify groundwater discharge zones in three streams in the Chesapeake Bay Watershed near smallmouth bass spawning areas. Paired groundwater and water samples from these three streams were analyzed for phytoestrogens (natural estrogens that occur in plants), herbicides (such as atrazine) and their breakdown products (such as hydroxyatrazine), steroid hormones, sterols (such as cholesterol) and bisphenol A. Chemicals detected in groundwater discharge zones were compared to those in the paired stream samples to better characterize the contribution of groundwater discharge as a contaminant source in the studied streams.
An important finding of this research was that phytoestrogens and herbicides were present in the streams and the corresponding groundwater discharge zones, with concentrations generally lower in the groundwater samples. The most frequently detected chemicals in this study were cholesterol (88 percent, fecal sterol), genistein (79 percent, phytoestrogen), atrazine (74 percent, herbicide), formononetin (55 percent, phytoestrogen), and metolachlor (50 percent, herbicide).
Sources/Usage: Public Domain.The Chesapeake Bay watershed, or draingage basin, encompasses six states - New York, Pennsylvania, West Virginia, Maryland, Deleware, Virginia, and the District of Columbia. A drainage basin is a giant system of creeks, streams, and rivers that all flow into a common outlet, which in this case is the Chesapeake Bay. Lower contaminant concentrations in groundwater discharge compared to those in adjacent streams indicate that runoff events are likely the largest episodic contributors of contaminant concentrations at the streams sampled, but groundwater discharge zones appear to be a consistent contributor of contaminants such as pesticides and phytoestrogens. Thus, these groundwater discharge zones represent a focused chemical exposure pathway in a habitat used by aquatic organisms during sensitive life stages, such as spawning. Although not quantified in this study, exposure of organisms to contaminants by way of groundwater discharge during sensitive early life stages could have harmful sublethal effects on growth, development, and reproduction with time.
This research was supported by the U.S. Geological Survey's Chesapeake Bay Priority Ecosystems and Fisheries programs, and the U.S. Geological Survey Ecosystems Mission Area’s Environmental Health Program (Contaminants Biology and the Toxic Substances Hydrology).
- Science
See below for other science related to this research.
Thompson, T.J., Briggs, M.A., Phillips, P.J., Blazer, V.S., Smalling, K.L., Kolpin, D.W., Wager, T. 2021. Groundwater discharges as a source of phytoestrogens and other agriculturally derived contaminants to streams. Science of the Total Environment, v. 755.
Drinking Water and Wastewater Infrastructure Science Team
The team studies toxicants and pathogens in water resources from their sources, through watersheds, aquifers, and infrastructure to human and wildlife exposures. That information is used to develop decision tools that protect human and wildlife health.Bioaccumulation of Mercury in Fish Varied by Species and Location in the Chesapeake Bay Watershed—Summary of Existing Data and a Roadmap for Integrated Monitoring
Fish mercury data from State monitoring programs and research studies within the Chesapeake Bay were compiled and summarized to provide a comprehensive overview of the variation in fish mercury concentrations among species and habitats within the watershed. These data are put into context with existing health benchmarks for humans, birds, and fish. Scientists also provide a roadmap for an...New Virus Identified in Melanistic Skin Lesions on Smallmouth Bass from the Chesapeake Bay Watershed
Scientists determined the risk factors associated with smallmouth bass melanistic skin lesions on smallmouth bass in the Susquehanna and Potomac Rivers, in the Chesapeake Bay watershed. A new virus, which appears to be a member of an emerging viral family, the Adomaviridae, was identified in the lesions. Questions remain about the full characterization of the virus and the role of environmental...Long-term Studies Examine Contaminant Exposure and Reproduction of Ospreys Nesting in Two Large United States Estuaries
In a series of studies from 2010 to 2018, U.S. Geological Survey (USGS) scientists detected low levels of legacy contaminants and pharmaceuticals in osprey (Pandion haliaetus) and their food chain within the Chesapeake and Delaware River estuaries. Osprey reproductive success increased during the same period and was determined to be adequate to sustain a stable population in both estuaries.Food Resources Lifecycle Integrated Science Team
The team studies the movement of toxicants and pathogens that could originate from the growing, raising, and processing/manufacturing of plant and animal products through the environment where exposure can occur. This information is used to understand if there are adverse effects upon exposure and to develop decision tools to protect health.