Polrot, A (2022) Understanding tributyltin biodegradation in muddy sediment for the adaptation of an anti-siltation technique with bioremediation potential. Doctoral thesis, Liverpool John Moores University.

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Abstract

Sediment siltation, the accumulation of sediment in navigable ways in ports, harbours and channels is a topic of concern for the management of these areas of high economic importance. Dredging, the conventional method to tackle siltation, has long been criticised for its high cost and detrimental environmental effects. Active Nautical Depth (AND) is one of the techniques which can be used in muddy ports and harbours to reduce dredging need and mitigate the environmental impact and cost of sediment management. The application of this method results in aeration of sediment and the proliferation of aerobic microorganisms. Many aerobes are known to degrade harmful contaminants commonly found in these highly polluted environments and therefore the application of AND could have a dual advantage of resolving siltation and contamination. The aim of this thesis is to evaluate the potential of AND to be used as a bioremediation technique, using tributyltin (TBT) as a model contaminant. The factors influencing TBT biodegradation in sediment were investigated in microcosm experiments, designed under different environmental scenarios. The variables used in the microcosms were temperature, agitation, aeration, mud type and time. To explore the microbial community involved in TBT biodegradation, the 16S rRNA genes of total bacteria in different microcosms were sequenced and community analyses were performed. Isolation of TBT-degrading and TBT-resistant bacteria was evaluated by comparing two methods of isolation and cultivation (standard plating and iChip). iChip greatly enhanced the success of cultivation of sediment bacteria. Several TBT-degrading and TBT-resistant isolates could be maintained in full laboratory conditions. Only Pseudomonas were able to use TBT as sole carbon source but members of Oceanisphaera were reported for the first time as TBT-resistant bacteria. The microbial community analyses highlighted a dominance of sulphate reducers and sulphide oxidisers in the sampled sediment, which likely persisted after aeration, spiking of 10 TBT and incubation of the microcosms. This study also reports for the first time the biodegradation of TBT at 4°C. At this temperature, biodegradation led to the accumulation of dibutyltin (which is also toxic), but it was degraded at 15°C. TBT biodegradation appeared to be inhibited by carbon and nitrogen amendment. This study suggests an applicability of AND throughout the year in temperate climates, including late winter when water temperatures are low. This contrasts with other studies which reported TBT degradation at warmer temperatures of up to 25-28°C. The parameters controlling TBT degradation are complex and field trials would be necessary to confirm and optimize the application of AND to a specific location before it can be adopted in the maritime industry as a bioremediation tool.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	bioremediation; tributyltin degrading bacteria; sediment contamination
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions:	Biological & Environmental Sciences (from Sep 19)
SWORD Depositor:	A Symplectic
Date Deposited:	08 Jun 2022 09:01
Last Modified:	13 Sep 2022 12:53
DOI or ID number:	10.24377/LJMU.t.00016997
Supervisors:	Kirby, JR, Birkett, JW and Sharples, GP
URI:	https://researchonline.ljmu.ac.uk/id/eprint/16997

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