Most of CSI’s efforts in the Cayuga Lake watershed go towards monitoring streams and creeks that flow into Cayuga Lake. Twice a year, CSI partners with the Floating Classroom to collect samples from Cayuga Lake itself, testing for the same parameters as in the streams. The trip out on the lake is one of the highlights of the 4-H20 Youth Science Club, whose participants have the opportunity to come on the boat with their families.
Collecting samples from tributary streams like Fall Creek, Salmon Creek, and Trumansburg Creek is crucial for understanding how land use impacts each watershed, how much pollution is present, and how quickly pollutants move through the watershed into the lake. Samples from Cayuga Lake show us if and how much the lake is being impacted by tributary streams.
One might expect that water quality in the lake would be some kind of average of the water quality in all of the streams, but it’s not that simple. Cayuga Lake is the longest of the Finger Lakes at just under 40 miles. Its surface area is 66 square miles, roughly the size of the Towns of Newfield or Lansing. Formed by melting glaciers during the last Ice Age, the east and west sides are steep and the north and south ends are shallow. With nearly 2.5 trillion gallons of water (2,499,535,920,000 give or take a few) Cayuga Lake varies quite a bit in its quality depending on where you look.
CSI’s monitoring focus lies at the southern end of Cayuga Lake. Although it has a depth of 435 feet, the “southern shelf”, which extends a few miles out from Stewart Park, is less than 25 feet in depth. This means that pollutants can become more concentrated in the southern shelf than in the rest of the lake. This could lead to problems like oxygen depletion and excessive algae growth. In deeper parts of the lake, the water becomes stratified into three layers: epilimnion, metalimnion, and hypolimnion. These layers are most distinct during the summer months, with water temperatures becoming more similar during the cold winter months.
The epilimnion is the water that is closest to the surface and is most susceptible to chemical and temperature changes. The water in the epilimnion is warmer in temperature than the rest of the lake and is primarily where fish are found during the summer. If you swim in the lake, you are in the epilimnion.
The metalimnion is the middle layer that separates the warm, surface water from the cool, deep water. This is where temperature changes most rapidly with depth. The metalimnion is relatively shallow compared to the other two layers.
The hypolimnion is the deepest, coldest water in the lake. Even in late August, the temperatures in the hypolimnion are just 6-8 degrees Celsius (40-45 degrees Fahrenheit). Despite the cold waters, the hypolimnion is home to a number of aquatic species, including lake trout. Cayuga’s hypolimnion is generally at a depth of 120 feet and below.
CSI collects most of its samples from the epilimnion, as that is where most changes occur, and grabs a few samples from the hypolimnion as well. If you’re wondering how one goes about getting a water sample from 150 feet down in the lake without scuba diving, check out the video below from the Floating Classroom about the special sampling device known as a Van Dorn Sampler that collects samples at any depth.
So how does the lake compare to the streams that flow into it? Visit the CSI Database to view and download results from stream or lake monitoring events! The results from the latest Floating Classroom trip can be viewed here: http://communityscience.org/database/events/1074
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