Molecular approaches for the study of bacterial biodiversity in sediments from contrasting regions of productivity in the deep Indian Ocean


Malinowska, Rachel Elizabeth (2009) Molecular approaches for the study of bacterial biodiversity in sediments from contrasting regions of productivity in the deep Indian Ocean. University of Southampton, Faculty of Engineering Science and Mathematics, School of Ocean and Earth Science, Doctoral Thesis , 349pp.

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Description/Abstract

Bacteria dominate the remineralization of organic carbon in marine systems. Examining
patterns of abundance, diversity and distribution is critical to understanding the
contribution of bacteria to global biogeochemical cycles. In the oligotrophic deep sea,
the role of bacterial communities is intimately linked to the flux of organic matter from
primary productivity in surface waters. Deep-sea sediments are a major site of nutrient
regeneration, supporting bacteria that comprise up to 90% of the benthic biomass and
account for almost 45% of all respiration that occurs in the deep sea. The study of
benthic bacterial communities in relation to organic matter flux may help to further
scientific understanding of the contribution of bacteria to trends in the carbon cycle that
have global significance.
In this study, the bacterial abundance and diversity in deep-sea sediments beneath two
zones of contrasting productivity in the Southern Ocean were compared. Sediments
were taken at two abyssal sites, to the east and south of the Crozet Island Archipelago,
in the Indian Ocean sector of the Southern Ocean. To the east of the islands, enhanced
productivity levels are generated by seasonal blooms in marked contrast to the
southerly, oligotrophic site where high nutrient, low chlorophyll conditions,
predominate.
Bacterial abundance was examined in sediment to a depth of 20 cm. No significant
difference in abundance was found between sites, although a trend in decreasing
abundance with vertical sediment depth was observed. Fluorescence in situ
hybridisation (FISH) showed consistent distribution of different bacterial groups at both
sites, where the gamma- and alpha-Proteobacteria were dominant. Similar denaturing
gradient gel electrophoresis (DGGE) profiles were observed for both sites. A
comparison of the eutrophic and oligotrophic surface sediment clone libraries found that
approximately 36% of operational taxonomic units were common to both sites,
however, richness was higher at the oligotrophic site.
The results indicated a consistency in abundance and community structure between the
two sediments, which may reflect shared biogeochemical characteristics. Both sites
supported the same dominant community members. Differences in richness were
observed between sites among the less dominant bacteria and these differences might
reflect the contrasting productivity regimes of the overlying water.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: University Structure - Pre August 2011 > School of Ocean & Earth Science (SOC/SOES)
ePrint ID: 69026
Date Deposited: 14 Oct 2009
Last Modified: 27 Mar 2014 18:48
URI: http://eprints.soton.ac.uk/id/eprint/69026

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