Sensitivity of the Marine Calanoid Copepod Pseudodiaptomus pelagicus to Copper, Phenanthrene, and Ammonia

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short‐lived planktonic larval stage, chronic life‐cycle toxicity tests using epibenthic copepods, and a 24‐h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48‐h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un‐ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH3/L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un‐ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221–1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.