Low flows of the Murray River due to water extraction have caused changes to the natural flooding regime of its floodplains. Environmental watering of the floodplains has been started as a strategy to enhance the ecological stability of these ecosystems. Hattah-Kulkyne floodplains has been experiencing the costs of low flows; under regulation, flooding frequency of the lakes in the floodplain has dropped dramatically. Environmental watering of the lakes started in 2005 and involves pumping water from the river into the lakes. Under this regulated flooding plan, the floodplain gets filled gradually with pumped water compared to the rapid inundation and recession under natural conditions. However, even with the current environmental flow regime, it is evident that lakes in these floodplains experience poor water quality; in particular, phytoplankton blooms are a major issue. This PhD project intends to identify the origin of bloom forming species, how these species’ dynamics change spatio-temporally and how the rapidly changing physico-chemical environment of the floodplain aid in their population dynamics. We further expect to identify how the phytoplankton population dynamics differ in lakes that get filled sequentially compared to lakes that get filled directly from the river. As the preliminary step, we are collecting data from Lake Kramen, which was dry for two years. Environmental watering/filling began in August 2019, and will continue for ~4 months. This offers a unique opportunity to observe phytoplankton dynamics throughout the complete filling and drying cycle of the lake (~2 years). We expect to generate suggestions to implement necessary mitigatory measurements for phytoplankton control at specific times of the watering events and further recommendations for the development of the current environmental flow regime to achieve most out of the water allocated for the environment.