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BGSU student’s research promotes reservoir health
Northwest Ohio is home to more than a hundred “upground” reservoirs. Unlike traditional reservoirs created by damming up streams and rivers, these are built alongside a river and water is pumped into them.
Like traditional reservoirs, they provide area residents both drinking water and recreation in the form of fishing. But what is good for one purpose is often in conflict with the other. While the Ohio Division of Wildlife stocks the water with yellow perch, walleye and channel catfish, efforts by water management officials to control harmful algae in the reservoirs by applying copper sulfate have had the unintended consequence of killing the food those fish depend upon, such as other algae, zooplankton (water fleas) and insects like midges and mayflies.
Research by Meghan Weaver, who is graduating from Bowling Green State University with a master’s degree in biological sciences, offers critical insight and hope for the situation that may help reservoir managers and state wildlife biologists work in coordination to achieve both their goals and preserve the “added value” recreation brings to a community.
She has been sharing her research with professional groups as the project progressed. She presented at the national meeting of the Society for Freshwater Sciences this summer, will meet with Ohio Division of Wildlife representatives at the district office in Findlay Aug. 6 and is scheduled to address the international symposium of the North American Lake Management Society in Madison, Wis., in November.
“Meghan determined through field investigations at reservoirs and in an elegant laboratory experiment that several sources of food for fish were severely reduced by even low levels of copper applied to these drinking water reservoirs,” said Dr. Jeff Miner, chair of the biology department. He and Dr. John Farver, geology, were Weaver’s mentors and oversaw her master’s thesis research.
The Erie, Pa., native developed a research project assessing the effects of copper sulfate on aquatic organisms in four northwest Ohio upground reservoirs. “Because my sampling was so intensive, I concentrated on four reservoirs,” Weaver said.
Many people, including former BGSU graduate student Ryan Crouch, have studied chemical, biological and physical variables of reservoir health, “but I found that no one had synthesized all these factors’ effects on the food web,” said Weaver, adding, “The project turned out to be not at all what I set out to do. It became so much bigger.”
Harmful algal species are a threat to safe drinking water, so reservoir managers regularly apply copper sulfate to the water’s surface, which interrupts the algae’s photosynthesis and cell division and kills them.
Copper sulfate is harmful to these reservoir’s food webs in several ways, Weaver said. First, it nearly eliminates zooplankton, an important food source for young fish. Second, the copper sulfate binds to particulate in the water and is absorbed by algal cells, both of which fall to the bottom, becoming part of the sediment. This matter is then eaten by larvae of chironomids — a type of nonbiting fly — that live in the sediment while they go through their four stages of development to adulthood. Chironomid larvae are an extremely important food for adult fish in upground reservoirs.
Weaver described the falling material as “like a lot of expensive energy bars raining down on a crowd of marathoners — which would be great except this food is full of copper, which is highly toxic.”
In the face of copper’s disruption of the food web, could both management goals — safe drinking water and robust fish populations — be met, Weaver asked.
Through endless rounds of sampling and experimentation, Weaver discovered that the most vulnerable time for the chironomids to eat the copper-contaminated food is during their first instar, or stage of development. “We found up to 85 percent mortality when the copper was applied during their first instar,” she said.
After that, while it still produced heightened mortality, the copper-contaminated food was not as lethal. Furthermore, she discovered that if copper sulfate is applied at lower concentrations, not as many of the zooplankton were kicked and their populations rebounded faster.
“The copper concentration in the sediment is astronomically high. We know that just living in the contaminated sediment produces a 40 percent mortality rate for the chironomids,” she said. “I wanted to see if the larvae were more sensitive to the ‘pulses’ of copper-laden food during the different stages of their development.”
Thus, Weaver found, if wildlife officials coordinate with water management officials to time the release of small fish into the reservoirs to avoid overlapping with the application of copper sulfate, many more fish could be saved by not having their food sources killed. Likewise, water management workers could avoid applying the copper when a “mass emergence” of chironomids is about to occur. “In any relationship, communication is important,” Weaver said.
She credits Miner and Farver for their guidance. “They were so supportive in allowing me to investigate my own avenue of research as it evolved,” she said. “Jeff provided the ecological side and John the analytical side. It was a great partnership and it was nice to be able to present an idea to them and get such a well-rounded critique of my work.”
Just like science itself, Meghan Weaver’s academic career has been a process of discovery. She received her undergraduate degree from Ohio Wesleyan University with a double major in zoology and English, hoping to eventually work as a science writer for publications like National Geographic.
“But I had an internship that convinced me that scientific research and conservation were where my true passion lay,” she said.
Her writing expertise has not gone unused, however, she said, but has been useful in communicating with water management personnel.
She has also had ecology research positions in the Florida Everglades and Pennsylvania streams. She will now take her expertise in ecotoxicology and aquatic ecology to Wisconsin, where she plans to seek a position with a natural resource agency.