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Blue carbon and edaphic influences on microbial metabolism: Bull Island’s sediments and polyhydroxyalkanoates (PHAs) distribution.

Grey, Anthony (2020) Blue carbon and edaphic influences on microbial metabolism: Bull Island’s sediments and polyhydroxyalkanoates (PHAs) distribution. PhD thesis, Dublin City University.

Bull Island, Dublin Bay is a Unesco biosphere and a unique example of a naturally driven, geo-engineered land mass arising as a by-product of marine processes, industrial and domestic human activities. Bull island supports a diversity of niche habitats, displaying tidal mudflats and wetland marsh, examples of a vegetated coastal ecosystems (VCEs), land types recognised as critical players in the long term global sequestration of C known as ‘blue carbon’ ecosystems. VCEs store comparable amounts of C to terrestrial ecosystems, despite much less area coverage and above ground biomass. Such land types provide invaluable ecosystem services through support of habitual biodiversity and as physical coastal buffer zones at urban and marine interfaces. The establishment and growth of VCEs are reliant on maintaining a balance between necessary inputs and outputs, thus the future of these carbon sequestering environments are highly vulnerable to climatic changes such as excessive nutrient/pollutant loading, temperature fluctuation and sea level rise leading to accelerated OM mineralisation by microbes and subsequent loss through CO2 emissions. As potential drastic shifts in the natural balance of VCEs becomes increasingly likely, a better understanding of the key regulators of C cycling is imperative to maintain and enhance the accretion of VCEs through natural carbon capture. Soils and sediments across Bull islands dynamic tidal habitats were investigated using a suite of analytical techniques where we observed some important abiotic/biotic/anthropogenic soil factors and the respective 1) correlations with and 2) effect on microbial community structure and metabolism. A combination of 16s alumina sequencing, Phospholipid fatty acid analysis (PLFA) and determination of - 2 - bacterial polyhydroxyalkanoates (PHA) concentrations provided evidence of bacterial metabolic adaptation in soils/sediments where elevated chemical stresses were observed. The microbial community structure was less diverse where pollutants increased and PHA levels increased, suggesting a potential role for bacterial PHA accumulation to allow for selective community establishment where soil toxicity increases. The occurrence of bacteria endowed with higher resistance to cell attack could have a significant role in maintaining C cycling in VCE soils where heavy urbanisation and anthropogenic stresses would otherwise inhibit microbial contributions. Stage-wise microbial processing of C from both autochthonous and allochthonous sources is a fundamental aspect of long term C storage in in blue carbon sediments. These processes relate to reduction in particle size and alteration of molecular structures to states facilitating transport to deeper layers and subsequent stability through processes including - formation of organo-mineral ligands, entrapment of C in micro-mineral structures and chemically induced reduction of microbial metabolic processes i.e. unfavourable redox conditions. Furthermore, the continued microbial metabolism of early stage OM in the rhizosphere horizons of sediments is strongly coupled to the cycling of essential plant nutrients, metals, gas exchange and chemical by products anthropogenic activities. These metabolic activities of adaptive microbes in the dynamic rhizosphere zones results in a positive feedback to above ground biomass enabling the continued succession of vegetation diversity, thus enhancement of C capture.
Item Type:Thesis (PhD)
Date of Award:2020
Supervisor(s):Kelleher, Brian and McCaul, Margaret
Subjects:Biological Sciences > Microbiology
Physical Sciences > Analytical chemistry
Physical Sciences > Environmental chemistry
Physical Sciences > Organic chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
Funders:Irish Research Council
ID Code:24970
Deposited On:23 Feb 2023 12:50 by Brian Kelleher . Last Modified 07 Sep 2023 04:30

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