Puarenga Stream alum dosing – summary of effects on lake biota 2013/2014

Abstract

Continuous alum dosing of the Puarenga Stream commenced in early 2010 to reduce inflows of dissolved reactive phosphorus to Lake Rotorua. Analyses of bioaccumulation in the tissues of macrobiota were undertaken in February 2013 and February 2014 for comparison to comparable samples obtained prior to and shortly after the commencement of alum dosing. No significant effects of alum dosing could be distinguished. Bioavailable aluminium in the vicinity of Sulphur Bay appears to be primarily influenced by the major geothermal activity of this region. No significant differences in aluminium bioaccumulation were observed in any species compared to samples obtained prior to the commencement of alum dosing. Continuous alum dosing of the Puarenga Stream since 2010 apparently has not resulted in adverse effects to Lake Rotorua shoreline biota nor caused any apparent increase in aluminium bioaccumulation in lake biota in the vicinity of Sulphur Bay.