Managing wetlands as off-river storages: Impacts on zooplankton communities

The competing demands of the environment and agriculture has challenged managers of waterways and prompted the development of new and novel ways of providing water for consumptive use without compromising the aquatic ecosystem. One partial remedy that has been proposed involves using wetlands as intermediary off-river storages to achieve consumptive benefits whilst maintaining ecological values. This study assessed the suitability of such a strategy by examining the impact of artificial drawdown on wetland zooplankton communities. An experiment was undertaken in outdoor mesocosms in which two treatments were compared over a 109-day duration: (1) partial artificial drawdown—where approximately half of the water was siphoned out after 42 days; and (2) natural drawdown—where the water was left to drawdown naturally via evaporation. Artificial drawdown only caused a small acceleration (<4 weeks) in the decline of abundance and density associated with natural population fluctuations, and temporarily changed the community structure. Furthermore, it had no effect on taxon richness, community composition and the initiation of dormancy. This suggests that wetlands could potentially be used for supporting consumptive demands whilst still maintaining abundant and diverse zooplankton communities, and hence a suitable food supply for higher order consumers such as fish and waterfowl.