The importance of small water bodies for carbon capture in Northumberland

Inegbedion, Otaigbe (2017) The importance of small water bodies for carbon capture in Northumberland. Doctoral thesis, Northumbria University.

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Abstract

Small water bodies (SWBs) are an important biogeochemical sub-compartment of the global carbon cycle that has been given little or no attention. They have similar capabilities to oceans, large lakes and river systems to exist in flux and could store more carbon in their sediments than the above systems. This research is aimed at determining the number and surface area of inland water bodies in Northumberland, the carbon stocks in the sediments of those water bodies and the microbial influence on the carbon stocks. These further define the Northumberland regional carbon stocks, the level of allochthonous and autochthonous carbon influence in the regional carbon stocks and the effects of surrounding vegetation, sediment wetness, dry bulk density, microbes, anoxia, pond permanence and temporariness on carbon stock variations.

The importance of SWBs is in their abundance and the ability to estimate this will aid the understanding of their actual contributions to the global carbon cycle as a net source or sink. Using Landsat-8 and World Imagery data, number and surface area of water bodies in Northumberland were identified by manual digitising of water bodies on ArcGIS 10.0. This showed variation in number and surface area of water body abundance with respect to imagery types, time and scale of analysis. The correctness of estimating water body abundance is subject to the continuous temporal change of small water body abundance. The continuous changes are associated with the nature of water bodies, regional/sub-regional landscape (hypsometry), precipitation and land use.

Carbon stock in Northumberland was determined by Total Elemental Analyser (TEA) combustion of sediment from various types and sizes of ponds collected from Druridge Bay, Northumberland. Carbon stocks varied in each ponds type and size range. These variations were influenced by the prevailing environmental/physical, biological and chemical/biochemical factors in pond sediments.

The microbial community drives carbon stock by altering the microbial community structure, allochthonous and autochthonous carbon processes and the oxygenation in the ponds. PCR pyrosequencing targeted at the 16s rRNA gene showed diversity in the microbial composition of the Northumberland pond sediments and the results showed a varying level of anoxia triggered by factors such as anoxic Proteobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria and Chlorobi dominance. These dominant phyla also influenced other phyla to develop anoxic ecological relationships and produce predominantly anoxia based processes like methanogenesis and fermentation. Anoxic pond bottoms were also triggered by high terrestrial inputs amongst other factors.

This research shows for the first time that carbon stock in a region’s SWBs varied because of numerous physical/environmental, chemical and biological factors. Also, SWBs stock carbon from the terrestrial environment and in-situ aquatic processes. Northumberland water body distribution has shown that more carbon is stocked in the small sized water body systems than larger water body system and their global abundance places them as an important carbon capture mechanism.

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