1H NMR-Based Metabolomics of Daphnia magna Sub-lethal Exposure to Organic Contaminants in the Absence and Presence of Dissolved Organic Matter
出版項
2019
說明
1 online resource (361 pages)
文字
text
無媒介
computer
成冊
online resource
附註
Source: Dissertations Abstracts International, Volume: 81-06, Section: B
Advisor: Simpson, Myrna J
Thesis (Ph.D.)--University of Toronto (Canada), 2019
Includes bibliographical references
Ecotoxicity tests which monitor observable endpoints such as mortality, growth and reproduction do not assess the molecular mode of action of contaminants in target organisms. Also, aquatic toxicity tests often do not include dissolved organic matter (DOM), which is ubiquitously found in natural waters. Hydrophobic organic contaminants sorb to DOM which may alter the bioavailability and toxicity of these contaminants. To assess this hypothesis, proton (1H) nuclear magnetic resonance (NMR)-based metabolomics was used to analyze the metabolome of Daphnia magna after acute sub-lethal exposure to organic contaminants in the absence or presence of DOM. Triclosan, carbamazepine and ibuprofen exposure resulted in different metabolic responses in D. magna. DOM at 5 mg dissolved organic carbon/L (DOC/L) did not change the D. magna metabolome from carbamazepine, imidacloprid or tris(2-chloroethyl) phosphate exposure, perhaps because these weakly hydrophobic contaminants do not sorb to DOM. The metabolic response of D. magna from 17α-ethynylestradiol (EE2) exposure was suppressed by 1, 2, 3, 4 and 5 mg DOC/L, likely from decreased EE2 bioavailability with DOM. The metabolic response in D. magna from perfluorooctane sulfonate (PFOS) exposure was not altered with 1 mg DOC/L. However, PFOS exposure with 2, 3, 4 and 5 mg DOC/L resulted in a unique metabolic response in D. magna, which may be due to enhanced PFOS bioavailability or combined action of PFOS and DOM on the metabolome. The metabolic response of D. magna from tris(2-butoxyethyl) phosphate (TBOEP) exposure was unaltered with 5 mg DOC/L, perhaps from the high potency of TBOEP. D. magna exposure to triphenyl phosphate (TPhP) with 5 mg DOC/L resulted in a unique metabolic response compared to TPhP exposure, possibly from combined stress of TPhP and DOM on the metabolome or altered TPhP bioavailability. The mode of action of mixtures of the hydrophobic contaminants triclosan, TPhP and diazinon in D. magna was not altered by 1 and 5 mg DOC/L. Overall, DOM may enhance or suppress the metabolic perturbations in aquatic organisms that originate from sub-lethal exposure to organic contaminants. Therefore, DOM should be included when evaluating molecular-level responses from sub-lethal ecotoxicity tests and during risk assessment of environmental mixtures
Electronic reproduction. Ann Arbor, Mich. : ProQuest, 2020
