Field and Experimental Studies on the Effects of a power station effluent on tubificidae (Oligochaeta,Annelida)

1. Higher numbers of sexually mature worms of L. hoffmeisteri were found in the River Trent downstream from Drakelow Power Stations than upstream.
2. The condenser effluent from the power stations not only increased the temperature of the river but also produced a considerable increase in the concentration of dissolved oxygen.
3. Experiments were therefore carried out on the effects of these two variables on the reproductive rate of the worms.
4. In these experiments it was found that: (a) L. hoffmeisteri increased its rate of egg production with increase in temperature up to about 25°C while T. tubifex maintained a fairly steady rate of egg production over a range of temperatures from 10–25°C. (b) L. hoffmeisteri maintained a fairly steady rate of egg and cocoon production over a wide range of oxygen concentrations above 2 ppm.
5. Therefore it seems likely that the difference between the numbers of sexually mature L. hoffmeisteri upstream and downstream from the power station were influenced more by the increased temperature, than the increased oxygen levels of the power station effluent, though under extreme conditions of deoxygenation, aeration of the river by the cooling towers at the power stations could increase the abundance of this species.