Toxicology of household detergents to reef corals

Ecotoxicological impacts (survivorship, growth) of two detergents, the linear alkylbenzene sulfonates (LAS) and the nonionic surfactants, nonylphenol ethoxylate (NPE), were examined on two branching coral species ( Stylophora pistillata and Pocillopora damicornis). Nubbins assays (n=1,890, 24-h exposures, 203-day monitoring) revealed high mortality in 1 and 5 mg/l detergents concentrations (for both species combined, LAS LC₅₀=1.99 mg/l; NPE LC₅₀=2.16 mg/l). Assays further showed detergent as species-specific mortalities (Stylophora LAS LC₅₀=1.00 mg/l; NPE=3.03 mg/l; Pocillopora LAS LC₅₀=2.21 mg/l; NPE=2.26 mg/l), also influenced by genotype-specific mortalities, phenomena which could downgrade genetic diversity of corals in the field, leaving frequently or chronically affected areas with detergent-resistant genotypes. Results revealed that LAS detergents were significantly more detrimental to coral nubbins than NPE detergents, resulting in high mortality and reduced tissue growth on substrates. Surprisingly, nubbins exposed to second and third LAS treatments exhibited significant higher survivorship levels than after the first exposure, whereas in all NPE treatments, nubbins' survivorship did not significantly differ in the repeated exposures as compared to the first set of assays. This outcome, while adding to our knowledge for the toxicity of various detergents, highlights the need to reduce repeated sewage spills. Furthermore, it is recommended that reef managers should emphasize disparate detergents' ecotoxicity on corals when establishing environmental policies.