Potential of the Biotic Ligand Model (BLM) to Predict Copper Toxicity in the White-Water of the Solimes-Amazon River

In this study, we evaluated the capacity of the Biotic Ligand Model (BLM) to predict copper toxicity in white-waters of the Solimes-Amazon River. LC50 tests using the species Otocinclus vittatus (Regan, 1904) were performed with Solimes-Amazon river water (100%) at 20%, 40%, 60%, and 80% dilutions. A sevenfold decrease in both dissolved and total Cu toxicity was observed in the experiment conducted with 100% when compared to 20% white-water, indicating that physicochemical characteristics of white-water attenuate Cu toxicity. There was agreement between the observed LC50 and the LC50 predicted by the BLM after the adjustment of critical accumulation concentration (LA(50)) for O. vittatus. BLM modeling indicated that dissolved organic carbon (DOC) and pH were the most important water parameters influencing Cu toxicity, followed by Ca2+. Our results highlight the first evidence that the BLM presents potential to predict Cu toxicity to aquatic organisms in the white-water of the Solimes-Amazon River.