| Abstract: | During a limnological investigation of the Holland River, Holland Marsh and Cook Bay of Lake Simcoe (Ontario, Canada), an evaluation was made of the magnitude and significance of nutrient contributions to the West Branch of the Holland River and to Cook Bay from mixed agricultural-woodland, mixed agricultural-urban, intensively cultivated marsh and uncultivated marsh subcatchment areas within the watershed. The importance of the “net input” concept is discussed in an attempt to assess the relative importance of contributions of nutrients from areas of different land use practices on the watershed. Recognizing the relatively high contribution of total phosphorus (2.1 kg P/ha yr) in drainage water pumped from the intensively cultivated marsh, changes in the management of the cultivated marsh are suggested which would conceivably reduce the phosphorus loss in drainage waters from these areas. |
