Macrobenthos of the cooling water discharge canal of the Gladstone Power Station, Queensland

Quantitative sampling of the macrobenthos of the cooling water discharge canal of the Gladstone Power Station has been conducted monthly from September 1976 to July 1980 (sampling times 1-47), to provide information on the effects of an initially small but increasing thermal discharge on this biota, and the likely effects that could be expected to occur in the Calliope River, which will ultimately receive a 65-m3 s-1 thermal discharge with a maximum temperature differential of 8.2° C when the power station is fully commissioned. Considerable fluctuation was found in the biotic data; however, the number of benthic organisms correlates more closely with flow rates in the canal than with any other abiotic factor, showing a positive correlation for sampling times 1-32, followed by a negative correlation for times 33-47. Times classification also indicated a major dichotomy at times 32-34. It is concluded that the changes in the benthos of the canal can be attributed primarily to changes in flow rates, which, in turn, have altered the sediment composition. This is supported by a change in the benthic fauna, with a gradual replacement of species of known sandy mud affinities by species living on or in stiff clays. With a design maximum temperature differential of 8.2° C and with lower water velocities outside the canal, the present data suggest that it is unlikely that the benthic fauna of the Calliope River, adjacent to the power station, will be markedly altered as a result of the thermal discharge; however, because of abiotic and biotic differences between the canal and the river, the testing of this extrapolation must await the analysis of the 'post-thermal' data presently being collected.