Niche partitioning of microbial populations in the Swan-Canning estuary

[Truncated abstract] The interaction of microbial populations in estuarine waters is a complex interplay controlled by various biological, physical and chemical processes. This study aims to determine how the spatial and temporal patterns of distribution of various microbial populations respond to the highly variable physical–chemical properties of an estuary, and particularly looking at the microbial–microalgal interactions. The study was conducted in Swan–Canning Estuary where fortnightly sampling was done for a period of one year (Dec 2008–Dec 2009). The microbial populations (bacterioplankton, virioplankton, picophytoplankton, nanophytoplankton and microphytoplankton) were quantified in conjunction with various physical and chemical parameters to understand the niche partitioning of these different groups and identify potential relationships between them. This approach was then applied during a short –term bloom event of the fish killing dinoflagellate Karlodinium veneficum in Canning River estuary. The initial study looked to explore the significance of picophytoplankton, and in particular Synechococcus spp., within the estuary. Flow cytometric analysis was used to quantify their abundance and characterise the picophytoplankton and Synechococcus populations. Spatial and temporal variability in their abundance was assessed in relation to the various physical–chemical parameters using statistical analyses including development of a General Linear Model (GLM). The picophytoplankton populations were higher from the middle to upper sections of the estuary and mostly abundant in summer.