SOURCES OF NUTRIENTS IN A KETTLE LAKE, MADISON, NEW YORK

Madison Lake is a 32-acre kettle lake in an area of coarse-grained glaciofluvial sediments located near Madison, New York. The lake is located very close to a surface water divide and has no outlets. Water flows out of the lake as groundwater during the summer and fall months. There are two small streams that enter the lake. One, an ephemeral stream, has not flowed during our study. The other stream starts in a small wetland 100 m north of the lake and had an estimated discharge of 0.002 m³/s from September to December 2014. Residents near the lake have noted that the clarity of the water has decreased and the amount of plant life, including the invasive seaweed Eurasian milfoil, has increased in the past ten years. Water quality data was collected sporadically from 1988 - 2011 and show a decrease in water clarity and increasing concentrations of total phosphorus and nitrate beginning around 2005.

We are studying the lake to determine the sources of nutrients that are causing the excessive plant growth and associated changes in water quality. We analyzed samples of lake water, stream water, and lake sediment for total phosphorus using ascorbic acid digestion and for nitrate using ion chromatography. We also extracted phosphorus from goose manure for analysis.

Our results show that phosphorus concentrations in the lake and stream are similar (average of 11.4 μg/l) and show little spatial variation. Several samples taken from a water depth of 5 m had slightly higher phosphorus concentrations. Phosphorus concentrations in lake sediment near stream mouths range from 7.8 to 9.6 mg/kg. Goose manure has high values of total phosphorus (up to 300 μg/l) and may represent a substantial source of nutrients to the lake. Nitrate concentrations in the lake are low (0.3 mg/l) and higher in the stream (8 – 10 mg/l). A small lake 1 km downgradient of Madison Lake with groundwater inflow has higher values of phosphorus and nitrate. We believe that the main sources of nutrients are farm runoff and goose manure. Farm runoff probably is the main source of nutrients but goose manure may be an important factor.