Chlorophyll and Production in a Polytrophic Marsh

Abstract

Abstract During the period 14 June to 4 October 1973, nitrogen, phosphorus and biomass determinations were carried out twice weekly in the waters of Cootes Paradise, Dundas, Ontario. In the western end of the marsh, biomass values (as chlorophyll a) were as high as 3900 mg/m3 with an average of 700 mg/m3. Total inorganic phosphorus was always in abundant supply ranging in concentrations of 1.2 ppm to 25.00 ppm. There was indication of mining of PO4, ‒P from the sediments of the Desjardins Canal under anoxic conditions. An inverse relationship was found between biomass and total inorganic phosphorus while there was no correlation between biomass and No3 ‒N overall. Average N:P ratios were low, generally less than 0.5. Nitrification of effluent ammonia was shown to be the major source of nitrogen. A periodicity in the effluent ammonia concentration preceeded increases in biomass. Biomass was dominated by Scenedesmus sp. Wind stress was found to have a significant influence on the changes in biomass. Average net production estimates were 1.65 gm O2/m2/hr with a maximum of 3.17 gm O2/m2/hr. The Dundas sewage plant effluent is the prime source of nutrients, both from the current effluent and from previously settled solids. Biological activity in the marsh is directly related to these periodic nutrient inputs. The west end of the marsh removes 80% of the PO4 before the water reaches the main area and therefore has a vital role to play in controlling the overall water quality of the marsh.