The Gippsland Lakes Ramsar Site (GLRS) located 200 km east of Melbourne is the largest estuarine lagoon system in Australia covering an area of 61,150 ha. The 2019-20 Black Summer bushfire burned 870,000 ha or 59% of the GLRS ecosystems. Since 1960, forest fire has become more frequent and larger in size in this region. Future fire seasons are expected to commence earlier and last longer, with decreased recovery time between fires. Extensive burning of the GLRS catchment area resulted in runoff loaded with ash, sediment and other pollutants. The Mitchell, Nicholson and Tambo rivers flowing into the Lakes were badly impacted and the inflows kept on recording high sediment loads even a year after the bushfire event.
Climate over the GLRS area has changed and this is projected to continue. The mean annual air temperature increased over half a degree from a 1986-2005 baseline and the number of hot days has also increased over the last two decades. With reduced rainfall, drought has dominated the region for much of the last three decades resulting in a decline in streamflow. Low streamflows are projected to continue. Relative humidity, important for fire weather, is projected to decline slightly in spring. Sea levels of the GLRS coastline are also projected to continue rising with more frequent extreme high sea-level events.
Ash and nutrients combined with high water temperatures have the potential to trigger increased microbial activity, which in turn can deplete the dissolved oxygen concentration (hypoxia) leading to large scale fish kills and other aquatic species loss. High nutrients loading into GLRS can also lead to potential toxic algal (cyanobacteria) blooms in summer months. Recommendations for water quality monitoring as well as knowledge gaps on the impacts of climate change on GLRS water quality will also be discussed in the talk.