New study highlights linkages among land use, water chemistry, and the health of Smallmouth Bass in the Susquehanna River watershed
Contaminants associated with agricultural and developed land uses may negatively affect SMB health and disease resistance in the Susquehanna River watershed.
Issue
Smallmouth bass (SMB) health and population structures have been negatively affected by changes in land use and water chemistry in some parts of the Susquehanna River watershed. Despite years of research, there is still much to be learned about the risk factors associated with SMB morbidity, disease, and juvenile recruitment. Comprehensive research about the associations between land use, water chemistry, and measures of SMB health can be used to inform regulatory decision making.
USGS Study
The potential SMB health issues in the Susquehanna River watershed led to a collaborative monitoring program by the U.S. Geological Survey and the Pennsylvania Fish and Boat Commission. This monitoring program was designed to assess the effects of water-quality and contaminants associated with agriculture and development on SMB health. Two sites impacted by divergent land uses in Pennsylvania were monitored from 2015 through 2019. One site is primarily forested and the other is impacted by a mixture of development and agriculture. SMB biological endpoints (at the molecular, cellular, tissue, and individual levels) and water-chemistry measurements were analyzed throughout the study to assess factors affecting SMB health over multiple seasons and years.
Major Findings
- The developed/agricultural site had more detections and higher concentrations of contaminants than the forested site (Table 1). Contaminants included a mixture of pesticides, wastewater compounds, hormones, phytoestrogens, and mycotoxins.
- SMB molecular and cellular changes were associated with more contaminants and land-use variables at the developed/agricultural site than at the forested site (Table 1).
- Liver gene transcripts associated with contaminants and land use at the developed/agricultural site included those related to immune/inflammation, oxidative stress, lipid metabolism, and stress. At the forested site, associations were observed between contaminants and liver gene transcripts related to oxidative stress, thyroid metabolism, cell proliferation, contaminant metabolism, and immune/inflammation.
- SMB from the forested site had a higher abundance of parasites in their liver and spleen than SMB from the developed/agricultural site. The higher parasite density at the forested site may have been caused by higher host availability (such as snails and birds).
Management Implications
Insights from this study can help management agencies identify the types of toxic contaminants and land use that can be managed to meet goals of clean water, sustainable fisheries, and healthier fish. Management practices that reduce runoff and decrease pesticide use could improve SMB health. Additional SMB health benefits may occur by reducing the use of cover crops that are known to have high phytoestrogen levels. Additional comprehensive assessments of fish health, land use, and water chemistry can help understand the impact of flow, landscape drivers, and timing of pesticide, fertilizer, and cover-crop applications on SMB health.
For More Information
- Contact Heather Walsh (hwalsh@usgs.gov)
- The full study has been published with open access in the Journal of Environmental Monitoring and Assessment: https://doi.org/10.1007/s10661-024-13049-4.
Contaminants associated with agricultural and developed land uses may negatively affect SMB health and disease resistance in the Susquehanna River watershed.
Issue
Smallmouth bass (SMB) health and population structures have been negatively affected by changes in land use and water chemistry in some parts of the Susquehanna River watershed. Despite years of research, there is still much to be learned about the risk factors associated with SMB morbidity, disease, and juvenile recruitment. Comprehensive research about the associations between land use, water chemistry, and measures of SMB health can be used to inform regulatory decision making.
USGS Study
The potential SMB health issues in the Susquehanna River watershed led to a collaborative monitoring program by the U.S. Geological Survey and the Pennsylvania Fish and Boat Commission. This monitoring program was designed to assess the effects of water-quality and contaminants associated with agriculture and development on SMB health. Two sites impacted by divergent land uses in Pennsylvania were monitored from 2015 through 2019. One site is primarily forested and the other is impacted by a mixture of development and agriculture. SMB biological endpoints (at the molecular, cellular, tissue, and individual levels) and water-chemistry measurements were analyzed throughout the study to assess factors affecting SMB health over multiple seasons and years.
Major Findings
- The developed/agricultural site had more detections and higher concentrations of contaminants than the forested site (Table 1). Contaminants included a mixture of pesticides, wastewater compounds, hormones, phytoestrogens, and mycotoxins.
- SMB molecular and cellular changes were associated with more contaminants and land-use variables at the developed/agricultural site than at the forested site (Table 1).
- Liver gene transcripts associated with contaminants and land use at the developed/agricultural site included those related to immune/inflammation, oxidative stress, lipid metabolism, and stress. At the forested site, associations were observed between contaminants and liver gene transcripts related to oxidative stress, thyroid metabolism, cell proliferation, contaminant metabolism, and immune/inflammation.
- SMB from the forested site had a higher abundance of parasites in their liver and spleen than SMB from the developed/agricultural site. The higher parasite density at the forested site may have been caused by higher host availability (such as snails and birds).
Management Implications
Insights from this study can help management agencies identify the types of toxic contaminants and land use that can be managed to meet goals of clean water, sustainable fisheries, and healthier fish. Management practices that reduce runoff and decrease pesticide use could improve SMB health. Additional SMB health benefits may occur by reducing the use of cover crops that are known to have high phytoestrogen levels. Additional comprehensive assessments of fish health, land use, and water chemistry can help understand the impact of flow, landscape drivers, and timing of pesticide, fertilizer, and cover-crop applications on SMB health.
For More Information
- Contact Heather Walsh (hwalsh@usgs.gov)
- The full study has been published with open access in the Journal of Environmental Monitoring and Assessment: https://doi.org/10.1007/s10661-024-13049-4.