Influence of Lake pH and Macrograzers on the Distribution and Abundance of Nuisance Metaphytic Algae in Ontario, Canada

Abstract

Thirty-six softwater lakes in central Ontario were sampled during 1988 to determine the relationship between metaphytic Zygnematacean algae and lake pH and the degree of complementarity between the presence of metaphyton and that of crayfish and tadpoles. A stratified sequential sampling program was developed to quantitatively measure and to objectively categorize average metaphyton abundance for each lake. A significantly greater proportion of lakes below pH 6 were found to contain extensive accumulations of metaphyton compared with lakes above pH 6. Lake pH and alkalinity were significantly correlated with metaphyton abundance. Macro-grazer density did not significantly influence the presence or absence of metaphyton, but reduced metaphyton abundance in those lakes which, because of their low pH or shallow depth, were predisposed to its accumulation. Managerial implications regarding the stocking of crayfish or tadpoles to limit the nuisance proliferation of metaphyton, and the importance of predaceous fishes in structuring this interaction, are discussed.