The Gowanus canal is one of the most polluted water bodies in the country. Birds, including juvenile herons (pictured), can nonetheless be seen off its shores (Adam Katzman/Gowanus Canal Conservancy)
News reports of a man claiming to have caught a three-eyed catfish off the shores of the Gowanus spread rapidly on the Internet, after a video appearing to show the mysterious creature surfaced on Sunday, Nov. 8. Experts were quick to dismiss it, questioning the presence of a freshwater bullhead catfish in the salty waters.
But the incident raises a question: So what does live in the famously polluted Gowanus?
The presence of catfish in the Gowanus – let alone a three-eyed example – might be highly unlikely, but a surprising diversity of microbial and marine life is not only thriving in the murky depths of the canal, it could also be showing signs of evolution.
“Once the founding individuals arrive in a place like the Gowanus canal, if they can survive and create a self-sustaining population, then the potential for evolution is there,” said Elizabeth Alter, a marine biologist at York College who studies microbial evolution in the Gowanus.
To a casual observer, the Gowanus Canal offers sights of various birds, particularly egrets, blue herons, and sea gulls. Blue crabs are also known to roam around pilings. Rats, New York’s biggest foe, could not be missing.
Below the surface, however, a variety of fish and microbial life inhabits the highly polluted waters.
Designated a Superfund site in 2010, the Gowanus Canal is “one of the nation’s most extensively contaminated water bodies,” according to the U.S. Environmental Protection Agency (EPA). With a long history of unregulated industrial waste dumped into its waters, and ongoing sewage spillovers, Alter sees the presence of fish in the canal as “pretty remarkable.”
Finding large marine species in the 1.8 miles long narrow stretch of the canal is not that far-fetched.
A 2011 report from EPA listed species collected from the canal during a study in 2010. These included striped bass, eel, and bluefish. These are not residents of the canal, but are believed to be ‘transient,’ flushed in from the East River and swept back out.
“It should be just about anything that you find in the East River,” she said. “There’s quite a bit more diversity than you might expect.”
Limited by minnow traps, eel is the only transient species Alter’s team has caught, but the biologist speculated that seahorse, puffer fish, toadfish and silverside are some the major species from the East River that could find themselves in the canal.
If visitors occasionally get flushed into the canal, only the most resilient can call the Gowanus home. Mummichogs, a species of small fish, are one of them.
Alter, who began studying mummichogs a year ago, thinks they may be one of the few permanent residents of the canal. She has observed the presence of juveniles, which suggests mummichogs are breeding in the canal, a strong indication the fish are populating the waters. Mummichogs are also known to be sedentary creatures, their typical home ranging in the tens of meters for their whole life.
“They don’t migrate,” Alter said. “So that also suggests to me that if anybody is going to be resident in the canal it’s probably this species.”
Mummichogs can eat and digest almost anything, owing their survival to their extremely diverse gut bacteria, which, according to Alter, could be playing a protective role for the fish.
“Microbes are essentially digesting [contaminants] before it hits the fish,” Alter said. “You can think of it as an adaptive response, the same way that cows and thermites have certain bacteria in the gut to help them break down grass or wood . . . we are hypothesizing that a similar thing is going on for these fish.”
An equally important resident of the canal are the archaea, a single-celled microbe known as an extremophile for its ability to live in extreme conditions. Alter and her team have found a higher number of Archaea in the canal’s sediments than one would normally find in other kinds of soil.
A large group of archaea is composed of methanogens, organisms that can survive in environments with little oxygen, producing methane gas as a byproduct of their metabolism. Their presence is a sign of the extreme conditions that exist in some parts of the canal.
How life in the Gowanus is evolving and in response to what, however, has yet to be clarified. The Gowanus remains a highly complex ecosystem marked by different sources of pollution. “To study the evolution, there are so many causal factors that we can’t pin point any particular pollutant because it’s a mix of everything,” Alter said. “We can say things are evolving fast, but what are they evolving in response to?”
Although heavy industries responsible for the canal’s contamination are gone, the Gowanus is not only affected by the long-lasting results of industrial waste, it also continues to be polluted by wastewater, limiting the possibilities for species than cannot survive in polluted, poorly oxygenated environments.
“The canal is still being polluted today, not by industrial waste and dumping, but by CSOs,”—combined sewer overflows, said Sean Di Luccio, Outreach Coordinator at the Gowanus Canal Conservancy, an environmental non-profit based in Brooklyn.
Sewer overflows occur when heavy rainwater and sewage water exceed the system’s capacity and spill into the canal. New York City’s sewer system combines both storm water and raw sewage into the same pipe. If treatment plants cannot meet the demands during heavy rainfall, the system is designed to discharge the excess flow into the city’s water bodies, which includes the Gowanus Canal.
The resulting spillover not only results in the injection of disease-associated microbes in the canal, it also leads to an overload of organic material and the appearance of microbes consuming oxygen at the expense of other species.
As part of the Superfund cleanup process—which is set to start in 2017 and cost $506 million—the EPA has drafted plans to build sewage storage tanks that will not prevent, but reduce the volume of raw sewage discharged into the canal. Contaminated sediment will also be dredged and capped with multiple layers of clean material.
What has or hasn’t swam in the Gowanus has long been the interest of New Yorkers, the most recent alleged discovery fuelling the sense of mystery that surrounds the canal’s dark green waters. Groups like the Conservancy and the Gowanus Dredgers Canoe Club, however, seek to change this public perception and educate people on an entire watershed that is often dismissed.
“We are trying to raise awareness like, ‘Hey, it’s getting cleaned up’,” Di Luccio said. “The canal has a bright future and there’s no need to attach stigma to it . . . one day its going to be a great place to live, work and play around.”