Phytoplankton populations of the Magela Creek system, Alligator Rivers, NT

1982

Open File Record 18
Kessell JA & Tyler PA
Supervising Scientist Division

Summary

The phytoplankton of the billabongs of Magela Creek is floristically rich and diverse. Some 500 hundred taxa have been recorded. Passively floating desmids and Chlorococcales, and motile flagellates are major components.

Species composition varies greatly from hour to hour and from site to site in any one billabong, with low (<50%) indices of similarity between successive samples. Algal scums are moved about the surface by changing winds, and clouds of motile flagellates appear to drift through the billabongs at discrete depths.

The distribution of chlorophyll in the water column varies greatly in space and time, over short distances and times (metres and hours), with at least a hint of active migration by motile species. The unavoidable picture is one of rich, heterogeneous and dynamic populations, kaleidoscopically changing by the hour or day. The taxonomic difficulties of a rich flora, the heterogeneity of the plankton, and above all its dynamism pose many problems for development of a monitoring programme, using algae, to detect low level heavy metal pollution, but the contribution of the plankton to overall food economy of the billabongs is likely to be high.