Effects of Neutralization and Early Reacidification on Filamentous Algae and Macrophytes in Bowland Lake

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Abstract
Within one year of neutralizing Bowland Lake (pH 4.8-5.5 increased to 6.3-6.7), previously extensive growths of filamentous algae et (Mougeotia and Zygogonium > 10 and 100% shoreline coverage, respectively) were essentialy eliminated (< 1% shoreline coverage). Reacidification in the second year (pH5.7-6.7) was accompanied by increased submerged epilithic and epiphytic growths of predominantly Zygogonium, often to preliming coverage. As found in other studies, pH .gtoreq. 6.0 appears to represent a threshold relative to the predominance of certain filamentous algae in softwater lakes. The short time between the change in acidity and the disappearance and reappearance of the filamentous algae suggests that they may be important biological indicators or predictors of acidification and its reversal. The changes in pH and alkalinity following neutralization did not substantially affect the macrophyte community in Bowland Lake. Macrophytes were restricted primarily to littoral areas less than 3 m in depth, despite excellent water transparency both before (SD = 8.0 m 1982) and after neutralization (SD = 4.5 m, 1985). Two uncommon species observed prior to neutralization (Eleocharis parvula and E. acicularis) were not observed afterwards, while two new and uncommon species (Nitella sp. and Brasena schreberi) were.