Hadal trenches account for the deepest 45% of the ocean (6000 - ~11,000 m). This environment is characterised by perpetual darkness, low temperature and high hydrostatic pressure. Amphipods dominate the scavenging fauna at these depths and are an ideal model organism with which to study this ecosystem. This thesis utilises an unprecedented data set, covering a bathymetric range of over 8000 m and across multiple hadal trench regions. I present both the first attempts at statistically robust ecological analyses of a hadal community and the first extensive examination of the biology and ecology of comparable fauna across multiple trenches. The distinction between “abyssal” and “hadal” communities varies between trenches. I posit that hydrostatic pressure and nutrient flux are primary drivers of community structure. While there is likely a boundary between the abyssal and hadal zones that is fundamentally set by a fauna's physiological limitations, there are also expected to be fauna that are specifically adapted to the environmental conditions (beyond pressure) of trenches. Within the hadal zone, food availability and associated competitive pressures appear to be primary drivers of population structure. Hadal amphipods accumulate extremely large (energy) triacylglycerol lipid reserves. These lipids are highly unsaturated, presumably to maintain metabolic accessibility under the solidifying effects of high hydrostatic pressure and low temperature. Species incorporate high proportions of 18:1(n-9) into their storage lipids, suggesting particular physiological importance. The membrane lipids of two hadal species are highly unsaturated, which I suggest is an adaptive mechanism to mitigate the harmful physiological effects of high hydrostatic pressure and low temperature. I find no evidence of differing physiological tolerance to pressure that would account for the zonation of the species. Rather, each species is understood to be specifically adapted to utilise the varying resources of the upper and lower hadal trench slope respectively.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:690570 |
| Date | January 2015 |
| Creators | Lacey, Nichola |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230045 |
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