Identification of the restrictive factors in the waters of Lake Varese
During the period May 1987 - March 1988, monthly samples were taken of the epilimnic and hypolimnic waters of Lake Varese in order to identify the factors which restrict the growth of algae. The nitrogen/phosphorous ratio, calculated as the ratio of total inorganic nitrogen to orthophosphate phosphorus, is between a maximum of 10 and a minimum of 3 in epilimnic waters and between 7.3 and 1.4 in hypolimnic waters. In general, in both epilimnic and hypolimnic waters, for the entire period of the experiment, iron was identified as the primary restrictive factor and nitrogen as the secondary restrictive factor. Inhibition of growth in the algae was only observed in the hypolimnic waters during the months of July and August. The A.G.P. values are between 1.7 and 58.5 mg/l dry weight for epilimnic waters and between 0.3 and 143 mg/l dry weight in hypolimnic waters. The significant correlations identified between the A.G.P. and the concentrations of orthophosphate phosphorus and inorganic nitrogen (r = 0.91 and r = 0.94 respectively) allow the potential growth of algae in the waters of the lake to be estimated by determining the concentration of orthophosphate phosphorus and mineral nitrogen. An equation has been developed which can be used to study the average biomass of indigenous phytoplankton from the A.G.P. values. Lake Varese has been judged to be in a state of advanced eutrophism with average values of A.G.P. of between 50 and 60 mg/l.
Bibliographic Reference: Article: Ingegneria Ambientale, Vol. 12 (1991) pp. 27-36
Record Number: 199111081 / Last updated on: 1994-12-02
Original language: it
Available languages: it