Multi-Way Data Analysis in Investigating Environmental Variables Regulating Cyanobacteria Species Abundances in a Major Drinking Water Reservoir

The present study provides a detailed understanding of the variation in cyanobacterial communities of Grahamstown Reservoir, a large shallow off-river storage servicing the city of Newcastle on the east coast of Australia. Receiving multiple inflows from two unprotected mixed land-use catchments, it is a model example of a reservoir highly vulnerable to adverse water quality issues, including phytoplankton blooms and their consequent filtration, toxin and taste and odour implications. The spatial and temporal distribution of cyanobacteria were assessed for a period of three years (Jan 2012- Dec 2014) based on samples collected fortnightly from three monitoring stations within the reservoir. Relationships between cyanobacterial abundance and a range of environmental factors was evaluated by application of Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) data analyses. MCR-ALS analysis indicated that among 22 physico-chemical variables and 14 cyanobacterial species measured, the vertical temperature gradient within the water column and nutrient availability, especially soluble reactive phosphorus (SRP), were the most powerful explanatory factors for the observed temporal and spatial distribution patterns in cyanobacterial species densities. The abundance patterns of the dominant cyanobacterial species, Aphanocapsa, Aphanothece, Microcystis and Pseudanabaena, were also strongly linked with rainfall and run-off patterns into the reservoir, while Dolichospermum (Anabaena) were more closely linked with the seasonal pattern of water temperature.