A new toxicity test with the Arctic algae Nitzschia frigida

• Main Author: Eldridge, Rebecca
• Other Authors: Hanson, Mark (Environment and Geography) de Jourdan, Benjamin (Environment and Geography), Mundy, C.J. (Environment and Geography), Jeffries, Kenneth (Biological Sciences)
• Format: Master Thesis
• Language: unknown
• Published: 2022
• Subjects: Aquatic toxicology; Bioassays; Environmental risk assessment; Marine toxicity tests; Reliability; Strength of methods; Arctic; Diatoms
• Online Access: http://hdl.handle.net/1993/36257

There is a pressing need to understand the impact of emerging contaminants on Arctic ecosystems; however, most standard toxicity tests are for temperate species. The lack of Arctic-specific tests may result in an underestimation of harm to Arctic organisms and contribute to significant uncertainty in risk assessments. As well, of the Arctic species tests that exist there has been no assessment of their reliability and relevance for use in environmental risk assessment. To help address these concerns, this thesis consisted of two phases: first, we conducted a critical review on the current state of Arctic ecotoxicology where reported effects were summarized, methodological reliability and endpoint relevance were assessed, and future testing needs were identified. We developed an objective scoring system and evaluated a total of 48 individual studies capturing 39 tested compounds, 73 unique Arctic test species, and 95 distinct endpoints published from 1975 to 2021. Our analysis shows that of 253 test substance and species combinations scored, 207 (82%) failed to meet at least one critical study criterion that contributes to data reliability for use in risk assessment. Significant data gaps were identified as it related to standardized toxicity testing with Arctic species, diversity of compounds tested with these organisms, and the inclusion of ecologically relevant sublethal and chronic endpoints. In the second phase of the project, we developed a laboratory bioassay for the Arctic diatom Nitzschia frigida. We optimized culturing conditions by testing various environmental conditions to determine which combination resulted in the most growth within a 14-day period. Under the resulting optimized conditions, we exposed N. frigida to copper, zinc, and 1-methylnaphthalene, with concurrent exposures of the standard, temperate species Skeletonema costatum in order to compare sensitivity. The test was consistent and repeatable based on control performance and EC50 results across three trials. N. frigida demonstrated ...