Factors Affecting Growth of Cyanobacteria in Malpas Dam: Causes and Consequences

Abstract

Blooms of cyanobacteria in Malpas Dam, a small reservoir on the New England Tablelands of NSW have been a recurrent aspect of the hydrological cycle in the dam since its construction in 1968. Specific concerns regarding their ability to produce toxins and their direct impact on various other aspects of water quality such as dissolved oxygen levels have made the management of cyanobacteria in the dam a prime objective for Armidale Dumaresq Shire Council (ADSC), the management body responsible for the dam. The general causes of cyanobacteria blooms in freshwater are widely understood however for each locality the exact combination of these factors can vary. In Malpas Dam previous research has indicated that the dam is eutrophic and regularly suffers from thermal and oxygen stratification, factors which are commonly the controlling influences on the establishment of cyanobacteria blooms. However the specific conditions which facilitate the growth of cyanobacteria in the dam remained a mystery. The research contained in this report includes the assessment of a range of water quality parameters in the dam and relates those to the establishment of cyanobacteria colonies. Further monitoring of catchment inputs to the dam was also performed and the influence these have on conditions in the dam in respect to cyanobacteria growth were evaluated.