Date of Award

Summer 2019

Document Type

Open Access Dissertation

Department

Environmental Health Sciences

First Advisor

Geoffrey I. Scott

Abstract

Global Climate Change may adversely affect the environment, increasing water temperature and altered salinity which may affect the toxicity of both legacy pollutants and Contaminants of Emerging Concern (CECs). Acute, 96 hour toxicity tests with adult grass shrimp (Palaemonetes pugio) assessed the effects of CECs (Polybrominated Diphenyl Esther (PBDE) – 47, ibuprofen, bifenthrin, triclosan, and bifenthrin/triclosan mixtures) under Standard Conditions (20°C, 20psu) and different Climate Change Conditions (30°C, and/or35psu) In addition, the grass shrimp microbiome (e.g. Vibrio bacteria) were assessed following acute triclosan exposures at the Maximum Exposure Concentration (MECs) and Minimum Inhibitory Concentration (MICs) under standard conditions. Colonies of Vibrio parahaemolyticus, V. vulnificus, V. cholerae and total vibrios from controls and triclosan exposed grass shrimp were enumerated and then isolates from each species were then tested for multiple antibiotic resistance. Statistical tests (Probit and Chi Square Analysis) were used to estimate LC50 values and to determine significant (p ≤ 0.05) differences (ANOVA and Dunnetts or nonparametric equivalents) in survival and levels of antibiotic resistance between controls and each CEC tested.

Results indicated that PBDE-47 under increased temperature and salinity conditions was more toxic, with a 96h LC50 of 31.30°C /L compared to 201.48 μg/L under Standard Conditions (30°C & 35 psu). Results for Ibuprofen indicated a 96-h LC50 under Standard Conditions (20°C, 20 psu) of 81.89 mg/L compared to 96-h LC50 ranging from 32.69 mg/ - 61.6 mg /L under different Climate Change Conditions of increased temperature and salinity (30°C; 20 or 35 psu). Bifenthrin under climate change conditions was more toxic with 96-hour LC50 of 96-hour LC50 of 43.74 ng/L compared to 53.47 ng/L under Standard Conditions. The triclosan LC5 under Climate Change Conditions was 325 μg/L compared to an LC50 of 580 μg/L under Standard Conditions. The triclosan and bifenthrin mixtures based upon Climate Change Conditions approached levels that were more than additively toxic (Additive Index = 1.00) with an Additive Index of 0.99 versus 1.32 for the Standard Condition Mixture. Exposure to triclosan MEC reduced Vibrio bacteria levels and both MEC and MIC exposure levels generally increased the antibiotic resistance of several of the 11 antibiotics tested.

Available for download on Tuesday, August 18, 2020

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