Temporal and spatial variations in the macroinvertebrate communities of the seasonally flowing portions of Magela Creek, Northern Territory

Department of Environment, Sport and Territories, 1997

Internal Report 240
Tripodi E
Supervising Scientist Division

About the report

The variations in the macroinvertebrate communities of non-permanent water bodies have received little attention in the past. Those studies which had been conducted were basically descriptive in content and pertained only to the wet-dry transition period. This is the first study to describe changes in the benthic macroinvertebrates throughout the tropical wet-season in the Alligator Rivers Region in northern Australia.

The temporal and spatial variations of the macroinvertebrate communities of Magela Creek in Kakadu National Park, Northern Territory were examined over the 1995-96 wet season. Three habitats were sampled (sandy tracts of stream bed, areas of macrophytic growth and leaf litter clumps) at three sites along the seasonally flowing portions of the creek using a modified semi-quantitative, rapid assessment technique employed by the Australian Monitoring River Health Initiative. Several sources of variation were identified. These included the environmental variables of macrophytic, detrital and integrated root mat abundance throughout the area of sampling transects, all of which were found to be significantly affecting the community indices used to describe the benthos (Simpson's Index of Diversity, number of taxa and total abundance). The highly variable flow regime and frequent spates which affected the creek during the study were the likely sources variation in the benthos. Multivariate analyses were used to determine the similarity between macroinvertebrate communities of different habitats, which were found to comprise of two major communities. The generalist detritivores which inhabited the macrophytes and leaf litter packs, and the highly specialised sand inhabiting community.

Although the physical, morphological characteristics of the channel structure of each study site were not recorded, these are believed to be the overall major cause for the variations observed between sites.