Zooplankton response to a multi-site environmental watering event during spring 2019 in the River Murray

About the document

During the 2019 Southern Spring Flow event , water for the environment was added to flows in the River Murray to help provide food and habitat for fish and other aquatic animals. The Southern Spring flow delivered water to several major wetland sites through thousands of kilometres of rivers. Monitoring results show the amount of food for baby fish—called zooplankton—increased during the Southern Spring flow.

These increases in water bugs are crucial food for baby yabbies, crays and small fish and means the River Murray food chain got a much-needed boost. The results showed a clear rise in zooplankton numbers immediately downstream of Barmah-Millewa Forest. This jump in plankton suggests that carbon was being flushed into the river during the August flow to fuel the food chain. Large numbers of very small water bugs (called rotifers) were also detected at lower Murray survey sites when the Spring Flow peaked in South Australia. This was most likely due to wetting of low-lying areas along the edges of the river, which provided ideal conditions for the growth of zooplankton that were then swept into the main channel.

A companion study (funded by The Living Murray Joint Venture) involved scientists at CSIRO monitoring how carbon and nutrients changed along the length of the river to understand whether the spring flow boosted the aquatic food web. CSIRO’s report is available here: 2019 Southern Spring Flow – Productivity Monitoring