Fish embryo and mysid tests as alternatives to standard fish tests for marine toxicity testing: a comparison of test sensitivity and exploration of additional endpoints

To protect marine environments, standardized whole effluent toxicity (WET) testing methods using a diverse range of aquatic organisms have been developed. A predominant method of WET testing is the fish larval growth and survival (LGS) test, which uses sheepshead minnow (Cyprinodon variegatus) or inland silverside (Menidia beryllina) larvae. Although fish LGS tests have been effective in the identification of potentially toxic effluents, animal welfare concerns have spurred efforts to develop and implement new approach methods, such as fish embryo toxicity (FET) and mysid (Americamysis bahia) survival and growth tests, which feature fish embryos and invertebrates, respectively. The goal of this study was to advance the development of marine testing alternatives by assessing the sensitivity of marine FET and mysid tests relative to that of standardized fish tests (i.e., fish LGS tests) for two environmentally relevant chemicals (i.e., Ni and phenanthrene [Phe]). In addition, the utility of sublethal endpoints as additional FET test metrics was explored. The findings of this study indicate that the mysid test is more sensitive than the other test methods evaluated for the assessment of Ni and Phe acute toxicity. Further, the mysid test showed comparable or greater sensitivity relative to the standardized fish LGS tests for the evaluation of chronic toxicity. Although the marine FET tests were less sensitive than the most sensitive fish LGS test for Ni and Phe, the inclusion of sublethal endpoints (i.e., pericardial edema and hatchability) increased FET test sensitivity. These findings indicate the predictive power of marine FET and mysid tests relative to fish LGS tests for the chemicals tested and suggest that FET test performance can be improved through the inclusion of additional endpoints. The results of this study lay the groundwork for future studies that aim to compare the performance of these test types using complex whole effluent mixtures.