The Relative Sensitivity of Four Benthic Invertebrates to Selected Metals in Spiked Exposures and Application to Contaminated Field Sediment

Abstract

The relative sensitivities of four benthic invertebrates (𝘏𝘺𝘢𝘭𝘦𝘭𝘭𝘢 𝘢𝘻𝘵𝘦𝘤𝘢, 𝘊𝘩𝘪𝘳𝘰𝘯𝘰𝘮𝘶𝘴 𝘳𝘪𝘱𝘢𝘳𝘪𝘶𝘴, 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 spp., and 𝘛𝘶𝘣𝘪𝘧𝘦𝘹 𝘵𝘶𝘣𝘪𝘧𝘦𝘹) were determined separately for cadmium, copper, and nickel in 96-hour water-only and in spiked sediment exposures. Survival (LC25's and LC5O's), growth and reproduction (IC25's) endpoints were compared amongst the four species. In the water-only tests, 𝘏. 𝘢𝘻𝘵𝘦𝘤𝘢 is the most sensitive species to cadmium and nickel, with mean LC5O's of 0.013 and 3.6 mg/L respectively, and 𝘊. 𝘳𝘪𝘱𝘢𝘳𝘪𝘶𝘴 is the most sensitive species to copper, with a mean LC5O of 0.043 mg/L. In the spiked sediment exposures, 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 spp. is most sensitive species to copper with a mean LC5O in sediment of 93 μg/g and a mean IC25 of 38 μg/g, and 𝘏. 𝘢𝘻𝘵𝘦𝘤𝘢 is most sensitive species to cadmium and nickel, with mean LC5O's of 33 and 67 μg/g respectively and mean IC25's of 10 and 40 μg/g respectively. Overall, 𝘛. 𝘵𝘶𝘣𝘪𝘧𝘦𝘹 is the least sensitive species to all metals tested, and the number of young produced/adult is the most sensitive of the reproduction endpoints for 𝘛. 𝘵𝘶𝘣𝘪𝘧𝘦𝘹. The relative sensitivities reveal that two endpoints, 𝘊𝘩𝘪𝘳𝘰𝘯𝘰𝘮𝘶𝘴 and 𝘏𝘦𝘹𝘢𝘨𝘦𝘯𝘪𝘢 survival, can be used to possibly distinguish between cadmium, copper, and nickel metal toxicity. Species test responses in field-collected sediments from areas contaminated primarily by the above mentioned metals were compared to the determined sensitivities in order to establish the causative agent of toxicity. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Responses in the field sediment support suspected toxicant in some cases, but not others. Multivariate analyses were used to assess sediment toxicity in the field sites based on the species responses, and these analyses reveal that the test endpoints respond to different environmental variables in ordination space. A comparison of test responses in the field sites to those in reference sites in ordination space reveals 13 of the 15 field-collected sites to be toxic or severely toxic.