Macroinvertebrates in Ephemeral Floodplain Wetlands on Gunbower Island, during environmental watering

"November 2009".

Project Number: An Ecological Evaluation of the Environmental Watering of the Gunbower Wetlands ICON Site in Relation to the Aquatic Animal Community - M/BUS/271.

MDFRC item.

The macroinvertebrate community at three ephemeral wetlands and three permanent wetlands associated with the Gunbower Island ICON site were investigated. A significant difference between ephemeral sites and permanent sites was observed and a clear pattern of community succession through time was displayed at ephemeral sites. Taxa richness was higher at permanent wetland sites, while density of macroinvertebrates was found to be higher at ephemeral sites. Nitrogen, phosphorus, carbon and tannins were found to be significantly higher at ephemeral sites, suggesting greater capacity for productivity than permanent sites. Animals that contributed most to dissimilarity between permanent and ephemeral sites were made up predominantly of the family Chironomidae. The macroinvertebrate population at ephemeral sites was dominated by the species Chironomus tepperi Skuse, a species well documented as being an important food source for water birds. Chironomus tepperi was not present in as high numbers at permanent sites where the dominant taxa were Oligochaeta. Of the 45 taxa that were found to be endemic to ephemeral sites, 22 were made up of animals of the Order Coleoptera, an Order well known for its adaptation to early colonisation. Results from this study have important implications for the use of recovered water for the environment. Ephemeral floodplain wetlands that are filled and allowed to dry out naturally have distinct macroinvertebrate communities and are therefore important for invertebrate biodiversity. They also support much higher densities of aquatic invertebrates that have known food web links to vertebrate species than associated permanent wetlands.