The influence of streams on nearshore water chemistry, Lake Ontario

Large lakes have characteristics, such as a spring thermal bar; nearshore offshore gradients of nutrients, sediment, and biota; and the development of a nearshore zone often chemically, biologically, and physically different from the offshore region, that are not commonly observed in smaller lakes. The research presented here focuses on the role of rivers affecting the cross margin transport of terrigenous materials delivered during the summer on nearshore waters of Lake Ontario. On the south shore of Lake Ontario, levels of chlorophyll, total phosphorus (TP), and total coliform were higher in the Oak Orchard Creek river plume than out of it. Similarly at the Genesee River polygon, turbidity, specific conductance, temperature, TP, and chlorophyll were substantially higher in the plumes than outside of the plumes. Graphic depictions and the strong correlations (r > = 0.70) between specific conductance and TP, soluble reactive phosphorus , temperature, chlorophyll, total Kjeldahl nitrogen, and turbidity indicate the plumes of water are from the Genesee River and Oak Orchard Creek. The load from all creeks on the New York shore of Lake Ontario ranged from ~ 18 to 25% of the annual phosphorus load of the Niagara River. The cumulative impact of these small streams entering the nearshore and embayments of Lake Ontario is potentially great, as the mixing of plume and lake water appears to be limited to the nearshore areas. Terrigenous inputs likely provide the nutrient, phosphorus, which contributes to the periodic development of benthic algae blooms observed along the south shore of Lake Ontario. The conclusion that river plumes impact and sustain the nearshore of large lakes is suggested by the data.

► We focus on the role of river water in transport of terrigenous materials in lakes.
► Turbidity, TP, and chl were substantially higher in than outside of stream plumes.
► The cumulative P load of streams entering the nearshore of Lake Ontario is great.
► Mixing of plume and lake water is limited to the nearshore area.
► River plumes help create and sustain the nearshore of large lakes.