Development of a test method for Chironomus riparius using a formulated sediment

The development of test methods which use formulated sediments is of importance for sediment ecotoxicology, because it provides the potential for improved control and hence reproducibility. The aim of this study was to evaluate the potential of a simple formulation, consisting of sand, kaolin clay, sphagnum moss peat and calcium carbonate, in a 10-day sub4ethal test with larvae of the dipteran midge Chironomus riparius. Tests showed that it was necessary to add food (tetramin) to obtain adequate growth and survival and that a rate of 1 mg per larva per day was optimum. This food must be available on the sediment surface; when food was mixed into the sediment there was a 95% reduction in the dry weight of larvae with respect to non mixed controls. The use of a flow-through versus a static system did not significantly affect dry weight of larvae.Manipulation of the composition of this sediment was also demonstrated to influence growth but not the survival of larvae in the test system.