Updating zinc guideline values for marine waters in Australasia: A species sensitivity distribution approach emphasizing local species data

Zinc is an essential trace element, but elevated concentrations from anthropogenic sources, such as stormwater runoff, wastewater effluent, and industrial discharges, can adversely affect marine organisms. Marine water quality guideline values aid management and risk assessment, but Australia and New Zealand values have been outdated. This study aimed to derive updated guideline values using chronic toxicity data relevant to marine species in the Australasian region. Chronic toxicity data were compiled from international and local toxicity databases and regional studies, totaling 350 values for 82 species. Guideline derivation prioritized studies with analytically verified zinc concentrations, low effect concentrations (e.g., EC10 values) and taxa native to or established in Australia and New Zealand, ensuring relevance to Australasian marine ecosystems. There were insufficient high-quality data, so the dataset was supplemented using estimates based on EC50 values, resulting in 16 species from seven taxonomic groups and a guideline value of 8.0 µg/L. Inclusion of nominal data instead resulted in a similar number of species and a slightly lower guideline value. Data gaps remain for key taxonomic groups, including fish, corals, and sponges, highlighting a need for quality toxicity tests using such species to provide more robust water guideline values. Despite ongoing gaps, the updated guideline value provides an improved basis for protection of regional marine ecosystems.