HR: 1340h
AN: GC33A-0939    [Abstracts]
TI: Potential Sources for Hypolimnetic Nutrients and Suspended Sediments in Southern Cayuga Lake, New York.
AU: Halfman, J D
EM: halfman@hws.edu
AF: Hobart and William Smith Colleges, Dept. of Geoscience and Environmental Studies Program, Geneva, NY 14456, United States
AU: * O'Neill, K A
EM: Kerry.ONeill@hws.edu
AF: Hobart and William Smith Colleges, Dept. of Geoscience and Environmental Studies Program, Geneva, NY 14456, United States
AU: Ware, T F
EM: Tara.Ware@hws.edu
AF: Hobart and William Smith Colleges, Dept. of Geoscience and Environmental Studies Program, Geneva, NY 14456, United States
AB: A routine survey of the seven largest Finger Lakes of central New York State revealed elevated concentrations of suspended sediment and soluble reactive phosphate in the hypolimnion (bottom waters) of Cayuga Lake. This observation is a concern because if these hypolimnetic nutrients are circulated to the epilimnion through natural processes such as wind-driven seiche activity and/or anthropogenic processes such as Cornell's Lake Source Cooling project, they could stimulate additional algal productivity and degrade Cayuga Lake as a source of drinking water. Here, we present the first of a two year study investigating potential sources for bottom water turbidity and nutrients. Surface, mid-depth (40m above the lake floor), and bottom water samples were taken at five sites following a mid-lake transect at the southern end of the lake. Samples were collected bi-monthly from May through September of 2007 and were analyzed in the laboratory for total phosphorous (TP), soluble reactive phosphate (SRP), dissolved silica (SRSi), nitrates, chlorophyll-a, total suspended sediment, and major ion concentrations following standard limnological techniques. A SBE-25 SeaLogger CTD profile of conductivity, depth, temperature, pH, dissolved oxygen, fluorescence and turbidity was also collected at these five sites, and two additional sites located near the mouth of two major streams (Taughannock and Salmon Creeks). Sites 2, B, and D revealed the thickest nepheloid layers, typically 20 m thick, and largest concentrations of bottom-water turbidity of 5 to 7 NTUs. In contrast, other sites located farther from these two tributaries or in shallower water revealed benthic turbidities of 1 to 2 NTUs. Total suspended sediment values were also high for the bottom waters of sites 2 and D. Turbidity increased after major wind events and minor rainstorms, however, lower rainfall in 2007 compare to previous years made it difficult to differentiate between fluvial and lake floor erosional events. The results suggest that these southern streams and/or winnowing of the nearshore sediments by wind- driven waves and currents may have a major influence on the lake floor turbidity. The bacterial decomposition of the algal biomass, indicated by an increase in SRP (up to 15 times surface concentrations) and dissolved silica with greater water depth suggests that biological contributions to the benthic nepheloid layer are important as well.
DE: 1848 Monitoring networks
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting