Effects of intervening Cross Lake on the Seneca River, New York
Effler, Steven W.; Effler, Adam J.P.; Prestigiacomo, Anthony R.; Perkins, Marygail; Driscoll, Charles T.
Water quality effects of intervening, hypereutrophic, dimictic Cross Lake on Seneca River (New York, USA) were assessed based on summertime fixed frequency monitoring of the river inflow to, and export from, the lake from 1999 to 2009. Monitored parameters included suspended particulate material (SPM), forms of nitrogen and phosphorus (phytoplankton nutrients), chlorophyll a (Chl), and chloride, as a conservative tracer. This was augmented by more frequent (daily) measurements of temperature and specific conductance from robotic monitoring platforms over two summers (2006 and 2009) at these two river locations, plus a pelagic lake site, to assess features of transport between the river and the lake. The river was found to enter and exit the lake's epilimnion during summer. Short-circuited transport of the river inflow to the lake outflow occurs during periods of high flow (upper quartile; > 70m3/s), which greatly reduces river-lake interactions. Flushing rates for the productive epilimnion are slow enough at lower flows to enable deposition of the larger particles in the river inflow within the lake and for the lake's hypereutrophic metabolism to be fully expressed in the outflow. Despite wide variations in the concentrations of the various constituents in both the river inflow and outflow, conspicuous signatures of the lake's effects were manifested that depict its functioning as: (1) a sink for SPM, (2) a sink for bioavailable forms of phytoplankton nutrients, and (3) a source of phytoplankton biomass (Chl). The functioning of Cross Lake, as a highly productive retention zone, plays a central role in sustaining dense downstream populations of zebra mussels, an exotic invader to the USA, in two important ways: (1) by increasing food concentrations in the form of phytoplankton and (2) through improvement of food quality. The associated deterioration of the oxygen resources in the river due to zebra mussel metabolism is a major problem for management of waste waters in the watershed.