Contamination of the environment by petrogenic hydrocarbons continues to pose a threat
to marine biota. Studies into the effects of hydrocarbon contamination have mainly been
directed at a small number of polycyclic aromatic hydrocarbons (PAHs) that are known to
be highly toxic to a wide range of biota. The majority of the hydrocarbons present in
sediments and tissues are unresolved by conventional gas chromatography and have
received little attention. Studies directed at these unresolved complex mixtures (UCMs) of
hydrocarbons have previously identified the monoaromatic fraction as containing toxic
UCM compounds.
The studies reported herein have explored the toxicity of UCM compounds to marine biota
using an effect-directed analysis approach: (i) population-level effects on the amphipod
Corophium vo/utator arising from chronic exposure to UCM hydrocarbon contaminated
sediments; (ii) bioaccumulation and depuration of UCM hydrocarbons by the blue mussel,
Mytilus edulis using comprehensive two-dimensional gas chromatography coupled to
time-of-flight mass spectrometry (GCxGC-ToF-MS); and, (iii) the possible trophic transfer
of UCM hydrocarbons from contaminated mussels to the predatory shore crab Carcinus
maenas.
Chronic sediment exposure tests showed that oils dominated by UCM hydrocarbons
reduced the growth rate and reproductive success of C. volutator. All fractions of the oils
contributed towards the toxicity but the aromatic fraction produced effects at lower
nominal sediment concentrations. The aromatic fraction was also responsible for the
reduction of mussel filter-feeding clearance rates. Analyses of mussel tissue extracts by
GCxGC-ToF-MS revealed that a range of aromatic compounds was rapidly accumulated,
but most were readily depurated. Compounds that were more resistant to depuration,
including branched alkylbenzenes (BABs), were also found in wild mussel populations
previously reported to have poor health status. Tests using a commercially available
complex mixture of C12.14 BABs confirmed that these compounds were toxic to mussels
and were not readily depurated. Crabs that consumed mussels contaminated with BABs
were found to behave abnormally, but cellular and physiological effects were not
significantly different to control organisms. Crab midgut gland tissues were found to
contain low concentrations of BABs and fluorescence from urine suggested that the BABs
were metabolised and/or excreted. The results did not support the hypothesis that BABs
were likely to biomagnify within the marine food web.
The research reported herein supports the hypothesis that environmental UCMs are
largely comprised of branched alkylated homologues of known petrogenic hydrocarbons.
Of these, the BABs have been shown to bioaccumulate and cause adverse effects via a
non-specific narcosis mode of action. Marine environment monitoring and regulatory
bodies may benefit from taking into account the concentrations of UCM hydrocarbons, in
particular the aromatic UCM, including the BABs.
Date of Award | 2007 |
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Original language | English |
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Awarding Institution | |
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Effect-directed analysis of toxicants in unresolved complex mixtures (UCMs) of hydrocarbons from biodegraded crude oils
Scarlett, A. G. (Author). 2007
Student thesis: PhD