The pH-independent effect of aluminum on cultures of phytoplankton from an acidic Wisconsin lake

摘要

Negative correlations between aluminum and planktonic algal abundance have been reported in acidic lakes. Natural assemblages of phytoplankton from a low-pH, low-Al lake (Franklin Lake, WI) were grown in semi-continuous cultures consisting of four treatments at pH 5.7 with 0.0, 50, 100, and 200 µg Al L−1and one treatment at pH 4.7 with no Al added.Asterionella ralfsiivar.americana(a common diatom plankter in acidic lakes) grew well at both pH 4.7 and 5.7 when no Al was added but declined in all other treatments and so may be useful as an indicator of acidic, low monomeric-Al conditions. Other common plankters that showed this pattern included:Arthrodesmus indentatus, Ar. octocornus, Ar. quiriferus, Staurastrum arachnevar.curvatum, S. longipesvar.contractum, andS. pentacerum. Common taxa showing no toxic effects of Al wereDinobryon bavaricum, Peridinium limbatum, Stenokalyx monilifera, Elaktothrixsp. andOedogoniumsp. We hypothesize that metal toxicity as a pulse at spring snowmelt could dramatically change algal succession in moderately acidic lakes. The experimental results agreed well with field observations. These types of experiments are useful for predicting the responses of natural phytoplankton communities to increases in Al concentrati