Limnological survey of eight billabongs in the Magela Creek catchment, Northern Territory

Abstract

A 6-week survey of the physicochemical limnology of eight billabongs in the Magela Creek catchment of the Northern Territory was conducted between December 1977 and January 1978. This covered the important period corresponding to the end of the dry season and the commencement of the wet season. Each billabong was sampled approximately weekly. At the end of the dry season. the billabongs' waters had elevated conductivity and turbidity, and generally higher sodium, potassium. chloride, phosphate, nitrate and chlorophyll a concentrations. They were generally slightly acidic and. in some. the bottom water was anaerobic. With the commencement of the wet season. the billabongs were flushed and a significant improvement in water quality was noted. Temperature. dissolved oxygen and redox potential data were used to tentatively classify these billabongs as polymictic. Under certain circumstances mixing did not occur for several days. during which time the bottom waters became significantly depleted in dissolved oxygen. On the basis of limited nutrient and chlorophyll a data, the billabongs at the end of the dry season appear to be mesotrophic.