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New Paltz undergrads monitor impact on sky lake

One of five “sky lakes” dug out by glaciers in the Shawangunk Ridge, Lake Minnewaska is a living laboratory for studying the impact—good and bad—that humans have had on the environment. 

As the lake has gone from being a crystal-clear haven for scuba divers to a murky paradise for large-mouthed bass and—as of this summer—leeches, it’s been a home away from home for SUNY New Paltz assistant biology professor David Richardson and his students. 

For years, an abundance of acid rain in the area made the lake incapable of hosting life much larger than zooplankton and salamanders; its relatively lifeless water shimmered an azure blue. Following amendments to the Clean Air Act that forced coal-burning power plants to minimize emissions and other possible causes, the pH of Lake Minnewaska rose to a more neutral level capable of supporting fish. 

One day golden shiners (a small minnow species) appeared in the lake; unchecked by natural predators, their population grew rapidly. By 2011, visibility in Lake Minnewaska was so compromised that park officials had to close the swimming beaches. 

Richardson, who has a long history of involving undergrads in research projects, saw this as an exciting opportunity to monitor the impact of introduced species. “The folks at Minnewaska and I became mutually interested in 2011,” says Richardson.  “I was working with a student, Stephanie Mogil, on a proposal for research, and we approached the state park managers about sampling. 

Simultaneously, the NYS Environmental Management Bureau, who samples all the state parks for environmental quality, was working on the project.” Richardson’s students from SUNY measured thewater clarity, the amount of algae in the lake, and the golden shiner population—introduced, Richardson conjectures, by a fisherman getting rid of extra bait fish—and concluded that the lake’s murkiness was the result of a trophic cascade:  the minnows consumed the zooplankton, which had kept the algae in check; the lake’s reduced visibility was being caused by the resulting algal bloom. 

Then, sometime in 2011 or 2012, large-mouthed bass found their way into the lake. Richardson conjectures that, like the golden shiners, they were dumped by a fisherman ignorant of the changes about to occur. As of this summer, the golden shiners are gone—consumed by the bass—and Lake Minnewaska has had to close its swimming beaches yet again, not because of reduced water clarity but because of the sudden appearance of leeches, which could have hitchhiked on the bass or water fowl. 

Richardson’s research reflects the developments as they occur. “With each change, we’ve had to shift the focus to new directions and questions. For example, we no longer have minnows, and leeches have become common, so the question for this summer has been focused around why the sudden shift in the food web occurred.” 

For answers, they’re fishing for leeches in the shallow water, where the tiny animals attach themselves to the students’ feet with their posterior suction cups. Thus far, Richardson et al have identified them as Helobdella stagnalis, and they aim to map the leeches’ spatial distribution, what they eat, and how they will overwinter in the lake. 

While most of their work consists of collecting, analyzing, and summarizing the data, Richardson’s students develop their own questions and design experiments within the framework of the project and also present their work at conferences and annual meetings about how to maintain the lake as a recreational resource. 

Says Richardson, “This research has been a really amazing collaboration between my undergraduate students, SUNY New Paltz, governmental agencies (New York State Department of Environmental Conservation and NYS Environmental Management Bureau and Minnewaska State Park), and private nonprofits (Mohonk Preserve and The Nature Conservancy). It has been really beneficial for the students to see both the science and management sides of this project. It also helps that Minnewaska is a beautiful and scenic place and the students get to hike, swim, and canoe all summer as part of their research projects.”

Tags Tags: SUNY New Paltz , Research , Student Research

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