Selection and sensitivity comparisons of algal species for toxicity testing

The sensitivity of 7 algal species representing the green and blue green algae was evaluated using EC50 values from the toxicity tests on 3 metal compounds (K2Cr2O7, CuSO4•5H2O, ZnSO4 and 3 formulated products of herbicides (oxyfluorphene, pendimethaline, atrazine). The growth inhibition tests were conducted in microplates. The variability in sensitivity was as high as 5 orders of magnitude (oxyfluorphene). The principal component analysis separated the cyanobacterial strain (Synechococcus leopoliensis) from the rest of algae representing Chlorophyta. The green algae were divided into two groups: first group with minute species (Chlorella kessleri and Stichococcus bacillaris) tolerant to herbicides and second group with the most sensitive species: Raphidocelis subcapitata (commonly known under synoym Selenastrum capricornutum), Scenedesmus quadricauda, Scenedesmus subspicatus and Chlamydomonas reinhardtii). The differences in sensitivity among the species of the second group were not distinctive. Therefore, any of these species, because of their similar sensitivity, can be recommended as test organisms in the single algal assays. However, toxicity results showed that none of these species can represent all the phylogenetic (taxonomic) groups of algae.