Evolution is often viewed through the lens of thousands of years. But it may have taken humans only a century or so to force evolutionary changes to fish in the Great Lakes, according to a Purdue University report.
Environmental factors over long periods of time often lead to beneficial traits in animals. But Tomas Höök, a professor in the Department of Forestry & Natural Resources at Purdue University and director of Illinois-Indiana Sea Grant, and colleagues believe there is evidence of fisheries-induced evolution (FIE) in the Great Lakes.
“Fishing and harvesting creates strong pressure that could select for certain genetic material in a fish population and lead to rapid human-induced evolution of the population,” Höök said.
A review, published in the Journal of Great Lakes Research, presents the case for rapid evolution, including case studies of two important fishery species — yellow perch and lake whitefish.
For yellow perch, Lake Michigan commercial fishing operations in the early 1990s overharvested perch, in particular large female fish. This led to an abundance of male fish as well as smaller females, since they were the most likely to have an opportunity to reproduce.
After a collapse of yellow perch populations, commercial fishing for the species was shut down and recreational angling for the species was restricted. Research shows that yellow perch quickly started to sexually mature later and at larger sizes once they weren’t susceptible to harvest.
“Importantly, this research suggests that FIE can occur rapidly, but that changes are reversible,” wrote the authors, which included Erin Dunlop from the Ontario Ministry of Natural Resources and Forestry, as well as Zachary Feiner and Höök from Purdue.
Lake whitefish populations have been affected by overfishing and invasive species in Lake Michigan and Lake Huron. Models suggest that high harvest rates and harvesting before whitefish reach sexual maturation could lead to rapid declines in population and the size at which fish mature.
Höök said fisheries-induced evolution has been widely studied in marine systems, but more needs to be done on freshwater species since many can be important ecologically and commercially.
“We need to assess the potential for fisheries-induced evolution in these systems to better understand the extent to which fishery managers can and should think about FIE when making key management decisions affecting fish populations,” Höök said.
After the third or fourth hour working on a paper, the practiced and true route of an English major like myself is to pop an Advil to quell the emerging headache and drink a few cups of coffee to keep writing. Now, as an intern at Illinois-Indiana Sea Grant (IISG), I am learning that along with a perfectly finished paper, I am inadvertently creating a harmful effect in a body of water quite near us. The drugs we put in our bodies end up in other places in addition to juicing our creativity–some end up flushed into Lake Michigan, along with other bodies of water. In 2010, IISG funded a study in which scientists took samples from Lake Michigan and found an interesting presence of drugs and chemicals that did not belong in the water.
Our bodies do not effectively digest the drugs that we ingest and, as a result, we excrete and flush them down the toilet. Then, the wastewater treatment plants do not always effectively remove the drugs and their by-products.
Wastewater treatment plants are designed to effectively filter used water and send it back into lakes and streams, but Lake Michigan, along with other water bodies, has been receiving outpourings of various medicines and personal care products, and into its clear waters for years. Studies done in 2013 found that only a few of the drugs that are flushed away are treated by wastewater treatment plants; the rest wind up undissolved in Lake Michigan where they remain, due to the fact that the active pharmaceutical ingredients remain intact. Researchers have found drugs as far as two miles away from sewage plants, suggesting that the lake was not diluting the compounds.
Why are these treatment plants, which have been designed specifically to filter wastewater, not effectively targeting and getting rid of the medicinal pollutants before they hit the sunny, boat populated shores of Lake Michigan? The unfortunate fact is that the treatment facilities were designed with other priorities in mind, and their technology is not always up to date. While the plants are effectively filtering out the trash and waste that was always evident in wastewater, only some drugs are being filtered out.
Drugs that are found in wastewater include commonly used medicines and hormones such as caffeine, acetaminophen, and estriol. They do not cause a disastrous problem though, due to their easy break down. On the other hand, many antibacterial compounds, found in soaps, toothpastes, antibiotics, and anti-inflammatory drugs, do not dissolve as easily. These compounds may cause issues for both the wildlife and humans who come into contact with the water.
There have been some effects of the water’s contamination measured in the lake’s wildlife. For example, studies show that a certain type of diabetes medication found in Lake Michigan has been affecting the hormonal system of fish that are exposed to it. To be specific, the Type 2 diabetes medication, Metformin, is disrupting male fathead minnows’ endocrine systems and thus affecting their procreation with female minnows. Other changes that wildlife are enduring are still under observation.
Wildlife in the water has constant exposure to this pollution. On the other hand, humans will not see immediate impacts but rather long-term changes, depending on each individual’s contact with the polluted water.
As of now, Lake Michigan’s water has not yet been proven to dangerously affect humans. The doses of each medicine are low in the great, large body of water. And there is no data that shows what effect such low doses have on people who may accidentally ingest the water when swimming in the lake, or whose cities may use the lake water as their water source. On the other hand, there is also such a large variety of medicines and personal care products in the water that the intermingling may prove a threat to our health down the road. However, the World Health Organization and the Environmental Protection Agency conclude that no immediate threat is posed to humans.
The treatment plants do, in fact, remove large quantities of medication from the water; however, since many drugs are coming in such a constant manner, it becomes harder to target the pollutants at a 100 percent efficiency rate. The recent reports of 2013 demonstrate a correlation between Lake Michigan pollution, and society’s constant use of prescribed medicines. Because many people are ingesting more drugs, more drug compounds end up in the water. People are also not familiar with the correct and environmentally efficient way to get rid of unwanted drugs. Many people naively flush the remnants down the toilet and flush their responsibility away with the drugs. But for the lake and its inhabitants, the issues are only beginning.
-Olivia Widalski, IISG intern
This is the first article in the series Lake Lessons written by Olivia about the issues surrounding pharmaceutical pollution and disposal.