Puarenga Stream alum dosing – effects on Lake Rotorua/Sulphur Bay biota 2016

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 2016 for comparison to comparable samples obtained prior to and since the commencement of alum dosing to satisfy annual resource consent conditions 8.7 and 8.8 of resource consent 65559.

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. Lake water chemistry in the vicinity of Sulphur Bay is heavily influenced by the direction of geothermal flows emanating from the Bay. 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 does not result in adverse effects to Lake Rotorua shoreline biota nor cause any apparent increase in aluminium bioaccumulation in lake biota in the vicinity of Sulphur Bay.