THE TOXICITY OF HEXAHYDRO-1,3,5-TRINITRO-1,3,5-TRIAZINE (RDX) TO THE FRESH-WATER GREEN-ALGA SELENASTRUM-CAPRICORNUTUM

RDX was not acutely toxic to the green alga Selenastrum capricornutum when tested at the solubility limit of the compound in algal assay media. A maximum reduction of 38% in cell density occurred after a 96-h exposure to 36.7 mg L-1; thus, an EC50 could not be determined . The lowest-observed-effect concentration (LOEC) and no-observed-effect concentration (NOEC) for the green alga were 4.8 and 0.5 mg L-1 (reduction in cell density), respectively, when chronic end points were used to analyze the data. A comparison of the data in this study with RDX toxicity data from the literature for the diatom Navicula pelliculosa, and the blue-green algae (cyanobacteria) Microcystis aeruginosa and Anabeana flos-aquae shows that S. capricornutum is the most sensitive to RDX. A U.S. Environmental Protection Agency (EPA) numerical water quality criterion Final Plant Value based on the green alga data should protect the above algal groups.