NUTRIENT VARIABILTY ASSOCIATED WITH MIGRATORY GEESE IN A SMALL LACUSTRINE ECOSYSTEM

Krystal Lake in Chazy, NY provides a unique opportunity to evaluate the impact of migrating waterfowl on a relatively simple lake ecosystem. The lake occupies a former limestone quarry that was abandoned in the early 1960s. The roughly rectangular lake basin is approximately 500 m long, 200 m wide and has a maximum depth of 18 m. The oligotrophic lake is predominantly groundwater fed with no permanent surface water inputs or outflows. The watershed is mostly undeveloped woodland and apple orchards. Each fall, geese, predominantly Canada (Branta canadensis) and snow geese (Chen caerulescens) use the lake as a staging area for about 3 months before departing farther south. Overnight goose abundances are variable, generally ranging from several tens to several hundred individuals and commonly exceeding 2000 individuals during peak migration. Distribution of goose species varies as the migration progresses, beginning with a high proportion of Canada geese but eventually snow geese become the most abundant. Preliminary estimates of potential phosphorus (P) and nitrogen (N) loads from geese are about 12.6 kg phosphorus (P) and 40.4 kg nitrogen (N) or 1.29 kg/ha P and 4.1 kg/ha N for the 2012 migration. These estimates are greater than similar studies from other areas.

Water quality indicators (nitrate-N, total phosphorus, soluble reactive phosphorus), biological oxygen demand, water temperature and total suspended solids were measured approximately weekly at a fixed sampling buoy through the late summer and fall 2012 and 2014. The lake becomes thermally stratified in the summer with epilimnion temperature typically reaching a maximum of 24–27 ^oC and extending to a depth of 7–8 m by mid-August. The onset of the goose migration generally coincides with the decay of summer thermal stratification but the lake is usually isothermal before the peak goose population is reached. Preliminary results indicate small nutrient increases during the goose migration period but the relationship is not predictable. The observed variations reflect complex abiotic and biotic interactions between base flow inputs, agricultural runoff, limnological processes, algal growth and decay and goose abundances. Our results may shed light on how geese can serve as drivers of nutrient exchange/flow in a relatively simple system.