Fish-eating gulls and terns nesting on Michigan shoreline areas known to have longstanding industrial contamination reproduce less, have fewer chicks that survive and develop more deformities than those on nonpolluted shorelines, a decadelong field study by Calvin University researchers found.
Keith Grasman, a biologist who studies environmental health effects at the Grand Rapids-based university, from 2010 to 2019 looked at reproduction, populations, fledgling growth and other health indicators among "colonial waterbirds" at specified contaminated reference sites, as well as at non-contaminated shoreline nesting areas for a comparison. The birds studied were herring gulls, Caspian terns, and black-crowned night herons.
The birds were assessed at known water-contaminated locations including the Saginaw Bay and River area of western Lake Huron; the River Raisin on western Lake Erie; and Grand Traverse Bay in northwestern Lake Michigan.
The Saginaw River and Bay and River Raisin areas are contaminated with polychlorinated biphenyls, or PCBs, a highly persistent industrial compound manufactured from 1929 until its banning in the U.S. in 1979. Grand Traverse Bay's pollution is chlorinated dioxins and furans, produced during the burning of waste or in the bleaching processes once used in paper mills, Grasman said.
The pollutants are biomagnifying — little fish eat tiny, contaminated invertebrates and the chemicals enter the fish's tissues. Then a bigger fish eats the smaller fish, and on up the chain, compounding the amount of the health-harming contaminants stored in each animal. It makes fish-eating waterbirds a good ecological marker for study, Grasman said.
"It doesn't look like an oil-floating-on-the-water kind of visible pollution problem, yet small amounts of these persistent chemicals can magnify as they go up the food web," he said.
The contaminated shoreline areas were compared to relatively uncontaminated waterbird nesting areas on the St. Marys River and Lake Superior. The contrasts were stark:
Nonviable embryos were two to nearly three times as prevalent in herring gull eggs from contaminated areas compared with the noncontaminated reference sites. A failure for eggs to fertilize and embryonic death were found at similar frequencies.
Bird embryos and chicks with deformities such as crossed bills and gastroschisis — being born with organs outside of the body — were found 12 times at contaminated sites and only once at a non-contaminated reference site.
Herring gulls at River Raisin and Caspian terns in Saginaw Bay "experienced complete or nearly complete colony-level reproductive failure in multiple years." Chick productivity "was poor in seven of 10 years" in the contaminated locations.
The population of herring gulls declined by about 90% from the late 1990s to 2019 at River Raisin. The number of nests and nesting area size in upland areas continued to decline even as rising Lake Erie waters over the last five years washed out beaches and applied pressure to nesting birds to relocate upland.
Similarly, the mean number of nests for the Caspian tern, a state-threatened species, at three islands in Saginaw Bay declined by about 49% over the last three years of the study compared with mean nest numbers from 1994 to 2003.
Gull chicks had poor growth metrics at the contaminated sites most of the years of the study — despite being in highly productive ecosystems with abundant fish prey. "Hence, the poor growth is not likely to be caused by food supply shortages in these locations but instead by other stressors such as environmental contaminants," the study found.
A test of immune functions in young birds found more than 50% lower response in contaminated zones than in non-contaminated comparison sites.
"If you go to the doctor and they do a bunch of diagnostic tests, and you have one abnormal test but everything else is normal, you are not going to be so worried about that," Grasman said. "But when we see multiple indicators of problems, that adds to the weight of the evidence for a significant issue."
The research was published this month in the peer-reviewed scientific journal Environmental Toxicology and Chemistry.
The Calvin University waterbird research is funded by the Great Lakes Restoration Initiative, federal funding approved by Congress to protect and restore the Great Lakes. Since its enactment in 2010, the initiative has funded more than 7,500 individual projects at a cost of more than $3.7 billion.
The Saginaw and River Raisin locations are known as "Areas of Concern," designated in the 1980s by federal governments in the U.S. and Canada, with local, state and provincial input, as known areas of extensive environmental degradation on or near the Great Lakes, diminishing the ecology and beneficial uses of the areas. The designation has helped focus binational cleanup efforts.
Grasman's work adds to a mosaic of Great Lakes-related scientific research findings across the region, with agencies such as the U.S. Environmental Protection Agency, the U.S. Fish and Wildlife Service and the Michigan Department of Environment, Great Lakes and Energy's Office of the Great Lakes then incorporating the data into their management decisions and priorities.
"Bird or animal deformities or reproductive problems" are listed impairments at the two Areas of Concern that EGLE is working with other partners to address, said Melanie Foose, Great Lakes Management Unit supervisor for the agency.
"Dr. Grasman’s research is extremely informative and valuable in Michigan’s Areas of Concern program," she said. "In the Raisin and Saginaw AOCs, colonial nesting bird colonies are a valuable line of research that we benefit from having, and we are pleased to be partners with the USFWS and Dr. Grasman on this work."
Grasman started studying environmental contamination's impact on waterbirds as a graduate student in 1991, and it became his life's work. More than four decades after many of the industrial contaminants plaguing areas of the Great Lakes were banned from use, and decades since the pollution levels of those contaminants then steeply dropped, the ecological impacts persist.
"It may be in some ways surprising that these older chemicals are still creating long-term effects," he said. "But now, as I think on it, with this much experience, it makes sense when I consider the long timeframes for ecological processes as well as for persistent chemicals."
Contact Keith Matheny: kmatheny@freepress.com.
