Flow cytometric methods for assessing water quality

Several Rotorua/Te Arawa lakes have undergone eutrophication and exhibit prolonged periods of poor water quality and cyanobacterial blooms. Sediment capping aimed at inhibiting the release of phosphorus from bottom sediments has been trialled on highly eutrophic Lake Okaro, as part of an ongoing remediation of water quality in the Te Arawa lakes. A modified zeolite product, Z2G1, developed by Scion as a phosphorus binding agent, was applied in September 2007 and August 2009, to inhibit the release of phosphorus from the sediment that occurs seasonally in the hypolimnion under anoxic conditions. While there has been considerable work on phytoplankton assemblages in eutrophic lakes, there has been relatively little work undertaken on other microbial components of eutrophic lake ecosystems, particularly bacteria and viruses. These micro-organisms have potential effects on algal community dynamics and nutrient cycling. The aim of this study was to investigate the possible inter-relationships amongst viruses, bacteria and algae, and the environmental factors that affect these relationships. Flow cytometry was used a rapid and effective method to assess the potential relationships between these micro-organisms and their effect on nutrient cycling in Lake Okaro.