Contaminants Affect Fish and Wildlife in the Chesapeake Bay

Science Center Objects

“Legacy contaminants” and “contaminants of emerging concern” that persist in the environment are affecting the health of fish and wildlife in the Chesapeake Bay and its watershed. State continue to report impaired water resources due to the persistence and toxicity of some previously banned pollutants. In addition, other contaminants of emerging concern are released to the environment at levels known, or suspected, to harm the health of fish and wildlife. Such is the major finding of a recent report on toxic contaminants in the Chesapeake Bay and its watershed. The report describes a study conducted by a team of scientists and managers from the U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, Hampton Roads Sanitation District of Virginia, and U.S. Geological Survey (USGS). 

Chesapeake Bay watershed, outlined in blue

Chesapeake Bay watershed, outlined in blue. Modified from USGS poster.The Chesapeake Bay Watershed.

The team reviewed State water-quality assessment reports, agency documents, and the peer-reviewed literature to summarize the state of knowledge about contaminants in the Chesapeake Bay watershed. This study is the first comprehensive review of contaminants (including polychlorinated biphenyls (PCBs), dioxins, polycyclic aromatic hydrocarbons (PAHs), metals, pharmaceuticals, pesticides, personal-care products, hormones, and others) that were scientifically evaluated for the watershed. The report will be used to help the Chesapeake Bay Program partnership make decisions about strategies to minimize the impact of contaminants on the environmental health of the Chesapeake Bay watershed.

The study team evaluated groups of contaminants in terms of their occurrence in water resources and associated bed sediment, as well as their known, or potential, effects on fish and wildlife. Several groups of contaminants (PCBs, PAHs, herbicides, and mercury) were widely distributed across the watershed, although only PCBs, mercury, and some organochlorine insecticides were determined to be of high severity in terms of adverse effects across the watershed or in local areas. Other groups of contaminants such as pharmaceuticals, hormones, and some pesticides were highlighted because the sources (such as wastewater discharges and agricultural land uses) are extensive throughout the watershed, even if monitoring data and information related to impairments are scarce.

Chesapeake Bay Technical Report Cover

Chesapeake Bay Technical Report Cover

(Public domain.)

The 2012 report is the result of the President’s Chesapeake Bay Executive Order (EO 13508) that directed Federal agencies to prepare a report summarizing information on the extent and severity of the occurrence of toxic contamination in the Chesapeake Bay and its watershed. USGS participation in creating the report was sponsored in part by the USGS Priority Ecosystems Science, Toxic Substances Hydrology, and Contaminants Biology Programs. The USGS participates in the Chesapeake Bay Program by providing data, conducting studies, and supporting scientists serving on technical committees and workgroups.

Health Effects

The report team used peer-reviewed literature (journal articles and other scientific publications) to describe the potential connections between contaminants and their health effects on fish and wildlife. The team found that the health of fish continues to be degraded by:

  • increased infectious diseases and parasites that cause fish kills,
  • feminization (intersex conditions) of largemouth and smallmouth bass,
  • reduced reproductive success of yellow perch, and
  • tumors in bottom-dwelling fish.

All these effects are likely related to toxic contaminants. In a few locations, contaminants adversely affect the health of wildlife, primarily birds, as evidenced by:

  • eggshell thinning,
  • death of embryos, and
  • failure of eggs to hatch.


U.S. Environmental Protection Agency, U.S. Geological Survey, and U.S. Fish and Wildlife Service, 2012, Toxic contaminants in the Chesapeake Bay and its watershed--Extent and severity of occurrence and potential biological effects--Technical Report--December, 2012: Annapolis, Md., U.S. Environmental Protection Agency Chesapeake Bay Program Office, 175 p.