LAKE LEVEL INFLUENCES ON SEDIMENT AND NUTRIENT RETENTION IN A LAKESIDE WETLAND

Lake levels, sediment and nutrient retention, and flows were studied in a 180-ha wetland adjacent to Lake Champlain, VT, to assess the role of lake levels on sediment and nutrient retention within the wetland. This wetland received both point and nonpoint sources of nutrients. Input, output, and within-wetland water samples were collected at 15 sites, and flows were measured nine times in 1983 at lake levels varying over 2 m. The ratio of wetland inflow to outflow was related to changes in lake levels. During spring, the concentrations of total suspended solids, total P, and total Kjeldahl N throughout the wetland were lower than during summer and fall periods. Wetland outlet concentrations decreased with rising lake levels. When wetland inflows exceeded outflow, there was a net mass retention of total suspended solids, total P, and total Kjeldahl N. Exports from the wetland decreased as lake level increased. The sediment and nutrient treatment capacity of this lakeside wetland appeared to be dominated by hydrologic influences.