DEVELOPMENT OF A TEST METHOD FOR CHIRONOMUS-RIPARIUS USING A FORMULATED SEDIMENT

The development of test methods which use formulated sediments is of i mportance for sediment ecotoxicology, because it provides the potentia l for improved control and hence reproducibility. The aim of this stud y was to evaluate the potential of a simple formulation, consisting of sand, kaolin clay, sphagnum moss peat and calcium carbonate, in a IO- day sub-lethal test with larvae of the dipteran midge Chironomus ripar ius. Tests showed that it was necessary to add food (tetramin) to obta in adequate growth and survival and that a rate of 1mg per larva per d ay was optimum. This food must be available on the sediment surface; w hen 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 w eight of larvae. Manipulation of the composition of this sediment was also demonstrated to influence growth but not the survival of larvae i n the test system.