Adult Corals Are Uniquely More Sensitive to Manganese Than Coral Early‐Life Stages

摘要

Manganese (Mn) is an essential element and is generally considered to be one of the least toxic metals to aquaticorganisms, with chronic effects rarely seen at concentrations below 1000 μg/L. Anthropogenic activities lead to elevatedconcentrations of Mn in tropical marine waters. Limited data suggest that Mn is more acutely toxic to adults than to early lifestages of scleractinian corals in static renewal tests. However, to enable the inclusion of sufficient sensitive coral datain species sensitivity distributions to derive water quality guideline values for Mn, we determined the acute toxicity of Mn tothe adult scleractinian coral, Acropora muricata, in flow‐through exposures. The 48‐h median effective concentration was824 μg Mn/L (based on time‐weighted average, measured, dissolved Mn). The endpoint was tissue sloughing, a lethalprocess by which coral tissue detaches from the coral skeleton. Tissue sloughing was unrelated to superoxidase dismutaseactivity in coral tissue, and occurred in the absence of bleaching, that is, toxic effects were observed for the coral host, butnot for algal symbionts. We confirm that adult scleractinian corals are uniquely sensitive to Mn in acute exposures atconcentrations 10–340 times lower than those reported to cause acute or chronic toxicity to coral early life stages, challengingthe traditional notion that early life stages are more sensitive than mature organisms.