Aquatic flora and fauna of the Marlborough Creek system

Seasonal changes in the aquatic flora and fauna of the Marlborough Creek system were studied in relation to the proposed Lagoon Hill Nickel mine in central Queensland, Australia. Nine sites on Marlborough Creek and two sites on a tributary (Spring Creek) were studied at the end of a prolonged dry season in November 1997 and results compared with those obtained approximately six weeks after significant wet season flows in April 1999. Seasonal changes in the physical and chemical conditions of the aquatic system are reported in a separate paper in these proceedings (Duivenvoorden et al. 2002). Aquatic macrophyte richness overall was very low compared to other permanent water sites in Central Queensland and general distribution had altered little between the two study periods. Aquatic invertebrate richness in 1999 was very similar to that in 1997, though there were fewer differences between sites. This is likely to be the result of the higher stream flows increasing oxygen levels and reducing some of the differences between sites that were apparent in the 1997 survey. A total of 66 different aquatic invertebrate taxa was recorded over the course of the two surveys. Taxa sensitive to environmental contaminants were very well represented, indicating a very healthy system. Further, results indicate that riffle areas are highly productive with regard to aquatic invertebrates. Fish species diversity (21 species) was relatively high for the size of the catchment and the significant populations of the Pacific blue eye (Pseudomugil signifer) found in the area are unusual in that they are usually found closer to the coast. Other aquatic vertebrates recorded include two species of crocodile and turtle. The 'vulnerable' Fitzroy River turtle (Rheodytes leucops) was not recorded, though it had been found in the system by one of the authors earlier on in 1999.