Comparison of the conventional algal assay and the Algaltoxkit F™ microbiotest for toxicity evaluation of sediment pore waters

Abstract

Conventional algal tests have not been utilized to their full potential for routine toxicity assessments. This is mainly due to the complexicity of these assays and the fact that many operators are still encountering practical difficulties. In view of the need for a cost-effective alternative to standard algal assays for routine testing, a new culture/maintanance free algal test was recently developed at the Laboratory for Biological Research in Aquatic Pollution of the University of Ghent in Belgium: the Algaltoxkit F™. In the present study, the conventional algal assay (OECD 201) and the alternative algal microbiotest, both using the micro-algae Raphidocelis subcapitata, were applied in parallel to evaluate the toxicity of 43 sediment pore waters collected from different water courses in Flanders (Belgium). The aim of the study was to compare the sensitivity of the 2 assays, performed in 50 ml erlenmeyers flasks and in 25 ml "long cells" (disposable spectrophotometric cells with a 10 cm pathlength) respectively. Both the conventional assay and the microbiotest were started with microalgae de-immobilized from algal beads. The 72h EbC50 values were calculated according to the ’area under the curve’ method recommended by the OECD. The results of the toxicity tests on the pore waters revealed a comparable sensitivity of the Algaltoxkit F™ test and the conventional algal assay. Furthermore, the repeatability of the microbiotest proved to be as good as — and in most cases even better than — that of the standard algal test. On the basis of the results obtained, it can be concluded that the Algaltoxkit F™ microbiotest is a valid alternative to the conventional algal assay, not the least for routine toxicity evaluation of sediment samples.