Growth, phenology, nutrient responses and ecological limits of the Ruppia Community and associated filamentous algal blooms of the southern Coorong

The Coorong, and Lakes Alexandrina and Albert Wetland in South Australia is recognised under the Ramsar Convention as a wetland of international importance. The foundation of the Coorong aquatic ecosystem is the macrophyte community dominated by Ruppia tuberosa but which also includes Althenia cylindrocarpa and another, potentially new, species of Ruppia (which together form the ‘Ruppia Community’). The Ruppia Community provides a range of critical ecosystem functions to the Coorong ecosystem, ranging from sediment stabilisation and maintaining water quality, through to a food source for water birds and shelter from predation for fish. The Millennium Drought (in particular the period from 2001 to 2010) significantly impacted the southern section of the Coorong (from Long Point to south of Salt Creek) including an almost complete decline of the Ruppia Community including their seed banks, which has decreased the resilience of the system. The recovery of the Ruppia Community has been gradual with the area occupied by plants increasing over the past decade. Recovery of the Ruppia Community in the Coorong South Lagoon has been limited by widespread, algal blooms; symptomatic of the lagoon’s hyper-eutrophic state. Algae, including mat-forming filamentous algae, physically disrupt the ability of the Ruppia Community to flower and set seed and have led to the widespread formation of black oozes in upper sediment layers.

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