Water Quality of the North End of Cayuga Lake: 1991-2006

The Seneca County Soil and Water Conservation District (SCSWCD) has collected limnological data on the waters of the northern end of Cayuga Lake since 1991. This report updates the 1999 report (Makarewicz et al. 1999) with data taken by the SCSWCD from 1999 to 2006. The purpose of monitoring the northern portion of Cayuga Lake was to determine the health of the Cayuga Lake ecosystem and to determine if any temporal trends existed in Cayuga Lake water quality. The water quality of Cayuga Lake has been studied since the early 1900s when secchi disk readings were first taken. At that time, the trophic state of Cayuga Lake was classified as oligotrophic; that is, nutrient concentrations and primary production were low and transparency high. Water clarity remained approximately the same up through the early 1930s. By the late 1950s, water clarity had decreased enough to classify Cayuga Lake as mesotrophic. Total phosphorus concentrations from the 1960s were well within the mesotrophic range and remained so until the late 1960s. Chl-a concentration also illustrated the trend toward more productive waters in Cayuga Lake in the mid 1960s through the 1970s. By the late 1970s, the transparency of Cayuga Lake had decreased to a nearly eutrophic value. In fact, in the early 1970s, some ranked Cayuga Lake as being the most eutrophic of the Finger Lakes of upstate New York. In a 2001 report, Callinan (2001) suggested an improvement in trophic state of Cayuga Lake by characterizing the main portion of Cayuga Lake borderline between oligotrophic and mesotrophic. Based on the sampling done by the Seneca County Soil and Water Conservation District from 1991 to 2006, an improvement in water quality of Cayuga Lake is suggested – at least at the north end where the samples were taken. Summer total phosphorus levels have significantly decreased and transparency of the northern end of the lake has significantly increased. Ambient chlorophyll levels were directly related to total phosphorus; that is chlorophyll, a measure of phytoplankton in the lake, was a function of phosphorus concentrations. As in the 1991-1998 period, the current (1999- 2006) trophic status of Cayuga Lake is currently best described as mesotrophic. In conclusion, water quality of Cayuga Lake appears to have improved since the early 1970s and also within the 1991-2006 period of monitoring by the Seneca County Soil and Water Conservation District