An osprey carries away a pipefish it snatched from Knapps Narrows near Tilghman Island, Maryland, on September 1, 2015. Also known as fish hawks, ospreys are harbingers of spring in the Chesapeake Bay region. The raptors begin arriving in early March and remain along the estuary’s shorelines, rivers and marshes through late summer.
In the mid-twentieth century, the widespread use of pesticides and industrial chemicals led to the near-collapse of the Chesapeake’s osprey populations. The pesticide dichloro-diphenyl-trichloroethane—known commonly as DDT—was causing female ospreys to lay eggs so fragile that they cracked under the parents’ weight. By 1972, when DDT was banned in the United States, there were fewer than 1,500 pairs of osprey in the Chesapeake Bay region.
High levels of polychlorinated biphenyls, or PCBs, have also been found in the eggs and chicks of ospreys that nest along the Bay. These industrial chemicals act as flame retardants and have been used in the production of inks, adhesives, sealants and caulk. While PCBs have not been produced in the United States since their ban in 1977, their ability to persist in the environment means the chemicals continue to be widespread in the region—and can expose ospreys to potentially harmful residue.
Despite the threat of these long-lasting pollutants, recent research has shown that ospreys are thriving in the Chesapeake Bay. As many as 10,000 pairs of the resilient raptors breed in the region—close to one-quarter of the osprey population in the contiguous United States.
As part of the Chesapeake Bay Watershed Agreement, the Chesapeake Bay Program’s Toxic Contaminants Workgroup is working to reduce the impacts that chemical contaminants have on the Bay and its rivers—and the wildlife and people that depend on them.
Image by Will Parson
Long-lasting chemical contaminants may still be persisting in the Chesapeake Bay region, but the pollutants have had no significant effect on the world’s largest breeding population of ospreys, according to a report from the U.S. Geological Survey (USGS).
While the three-year study found some residue of pesticides and industrial chemicals in the Bay’s tidal waters, fish, osprey eggs and osprey chicks, researchers did not find a connection between the fish hawk’s exposure to the chemicals and its success in the Chesapeake region.
“Osprey populations are thriving almost everywhere in the Chesapeake,” Rebecca Lazarus, a researcher at the USGS’ Patuxent Wildlife Research Center and the lead author of the report, said in a release. “We found them nesting in some of the most highly contaminated areas in the Bay and we did not find any relationship between contaminants and their nests' productivity.”
Widespread use of DDT in the mid-twentieth century caused the Bay’s osprey population to fall to fewer than 1,500 pairs before the pesticide was banned in the United States in 1972. Close to 10,000 pairs of osprey are expected to nest in the Chesapeake region this year.
To hear Lazarus describe osprey life history and her research, watch our Bay 101: Ospreys video:
The study, "Chesapeake Bay fish–osprey food chain: Evaluation of contaminant exposure and genetic damage," is available online from the journal Environmental Toxicology and Chemistry.
Chemical contaminants continue to afflict the Chesapeake Bay watershed, raising concern over water quality and the health of fish, wildlife and watershed residents.
Close to three-quarters of the Bay’s tidal waters are considered impaired by chemical contaminants, from the pesticides applied to farmland and lawns to repel weeds and insects to the household and personal-care products that enter the environment through our landfills and wastewater. But so-called “PCBs” and mercury are particularly problematic in the region, according to a report released last week by the U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (USFWS).
Both PCBs—short for “polychlorinated biphenyls”—and mercury are considered “widespread” in extent and severity, concentrating in sediment and in fish tissue and leading to fish-consumption advisories in a number of rivers and streams.
The District of Columbia, for instance, has issued such advisories for all of its water bodies, asking the public not to consume catfish, carp or eels, which are bottom-feeding fish that can accumulate chemicals in their bodies. While the District’s Anacostia and Potomac rivers raise the greatest concern in the watershed when it comes to fish tissue contamination, a November report confirmed that many Anacostia anglers are sharing and consuming potentially contaminated fish, sparking interest in reshaping public outreach to better address clean water, food security and human health in the area.
While PCBs have not been produced in the United States since a 1977 ban, the chemicals continue to enter the environment through accidental leaks, improper disposal and “legacy deposits”; mercury can find its way into the atmosphere through coal combustion, waste incineration and metal processing.
Exposure to both of these contaminants can affect the survival, growth and reproduction of fish and wildlife.
The Chesapeake Bay Program will use this report to consider whether reducing the input of toxic contaminants to the Bay should be one of its new goals.
The Bay Program Toxics Subcommittee has updated its list of Toxics of Concern, ranking the toxic organic chemicals in the Chesapeake Bay with the most potential for harm. PCBs topped the list, followed by PAHs and organophosphate pesticides. Organochlorine pesticides and five other organic toxics are also included in the list.
The original Toxics of Concern list, which was completed in 1991, identified and documented chemicals that were adversely impacting or had the potential to impact the Bay. The list was subsequently refined in 1996 and 2000 prior to this latest update.
The 2006 Toxics of Concern list is based on the same chemical ranking system used for the 1996 list, incorporating chemicals' source, fate and effects of exposure. Also, like the 2000 list, fish consumption advisories and 303(d) impairments were considered for the 2006 revision.
The Toxics of Concern list is used by the Bay Program Toxics Subcommittee to help develop strategies to address the most problematic toxic organics in the Bay and its tributaries. It is not a complete list of all chemicals that may impact the Bay or its watershed. Some organics could not be included due to data gaps. Also, metals, such as mercury, are not included in the list because assessment guidelines comparable to those used for organics are not currently available.
Although PCB manufacturing was banned in 1977, PCBs can build up in bottom sediments and persist for many years; therefore, historic discharges of PCBs can still affect the Bay today. Also, when old PCB-containing equipment that is still in use fails, PCBs can flow into the nearest stream or river via stormwater.
PAHs are formed when coal, gasoline and fuel oil are burned and are a major component of tar and asphalt. The most rapid increases of PAHs in river bottom sediments are found in watersheds with increasing development and motor vehicle traffic.
Organophosphate pesticides are mostly herbicides and insecticides used in agriculture. Organochlorine pesticides, such as DDT, are no longer widely used but persist in the environment.
In recent years, people have become increasingly concerned about the issue of toxic materials, like Polychlorinated Biphenyls (PCBs), contaminating fish and shellfish in water bodies around the world. In the Chesapeake Bay region, the Bay states have issued fish consumption advisories throughout the Bay and its rivers to protect the health of people who enjoy dining on the Bay's fish and shellfish.
One way that Bay scientists assess how toxic pollutants are affecting the animals and plants in the region, Bay Program partners have focused on PCB concentrations in local white perch. PCBs are persistent organic chemicals that were formerly used in industrial practices in the United States. They enter the environment and can impact the creatures living within it. Although PCBs are not the only contaminants in an area, PCB concentrations in white perch provide an indication whether other chemical contaminants are present in an area.
White perch are a good indicator of toxic contaminant concentrations in the Bay's waters because they are a resident species in the Bay; the majority of white perch remain in local waters throughout their lives. Considered an enjoyable fish to eat, white perch are a commercial and recreational fishery in the Bay. For scientists who are examining the effects of chemical contaminants on fish, as well as the impact on humans who eat PCB-contaminated fish, white perch are a logical species to study.
Data gathered from Maryland and Virginia suggests that PCB concentrations are higher among white perch in the upper Bay than they are in the lower Bay. Similarly, there is a trend in fish tissue where fish on the eastern shore have lower concentrations of PCBs than their counterparts on the western shore.
A common characteristic among the areas of the Bay where white perch have higher PCB concentrations is related to land development; the western shore of the Bay is more developed than the eastern shore of the Bay, and white perch from the Bay's western shore have higher PCB concentrations than their counterparts on the eastern shore. Additionally, white perch sampled from the Patapsco River had particularly high PCB concentrations, which can be attributed to the level and type of industrialization in the Baltimore area.
Many of the Bay's waters have active advisories for limiting the consumption of white perch. As is true with any fish, it is important for someone who plans to catch white perch in the Bay's waters to first check out the fish consumption advisories to see what the state recommends regarding consuming fish caught in the Bay and its rivers.
Without sufficient data to determine a trend in the PCB concentrations in white perch in the Bay, Bay scientists cannot say for sure what to expect regarding the future of those toxic contaminants in white perch in the Bay. However, PCBs were banned more than 25 years ago, so scientists expect to see a natural decrease in their concentration in white perch over time.
Chemical contaminants that get into the environment and harm the animals and plants around them are typically considered to be toxic pollution. Learn about toxic pollution in the Bay.