Physical and chemical characteristics of the nearshore zone of Lake Ontario

Abstract

A long-term, 7-year lake-wide study was paired with a short-term intensive nearshore study to characterize water quality conditions of coastal Lake Ontario in New York. Mean total phosphorus (TP) concentrations in rivers (84.3±7μg P/L), embayments (129.7±9.6μg P/L), and shoreside sites (61.9±7.4μg P/L) exceeded the IJC goal of 10μg P/L for Lake Ontario waters and were significantly higher than in offshore waters (L0-100m, 9.5±0.7μg P/L; LO-30m, 10.4±0.08μg P/L). In three 5×20-km regions of the nearshore located at Oak Orchard, Rochester, and Mexico Bay, TP levels exceeded the 10μg P/L goal for Lake Ontario in 48% and 32% of the samples in June and August, respectively. Also, shoreside and embayment chlorophyll a were significantly higher than in offshore waters. Elevated sodium levels observed at shoreside sites of Lake Ontario are likely due to the heavy use of salt during the winter to deice roads. The elevated phosphorus concentrations observed at the shoreside sites extended into Lake Ontario. For example, at the Rochester nearshore sites in June, both TP and turbidity were elevated out to at least 4km from the shoreline, whereas temperature and specific conductance were elevated out to 3km from the shoreline. Shoreside sites had some chemical characteristics distinct from both the offshore (LO-30m and LO-100m) and river sites within the sampling polygon. A thin band of water with a unique water chemistry compared to both the offshore waters and tributaries extends up to 4km into the open waters along the southern coast of Lake Ontario during the late spring and summer.