Benthic foraminiferal responses to mesoscale environmental heterogeneity at the Porcupine Abyssal Plain, NE Atlantic
Although our knowledge on the vast deep-sea biome has increased in recent decades, we still have a poor understanding of the processes regulating deep-sea diversity and assemblage composition, as well as their underlying natural variability in space and time. In the face of unprecedented anthropogen...
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| Format: | Thesis |
| Language: | English |
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2016
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| Online Access: | https://eprints.soton.ac.uk/403394/ https://eprints.soton.ac.uk/403394/1/Stefanoudis%252C%2520Paris_PhD%2520Thesis.pdf https://eprints.soton.ac.uk/403394/2/Stefanoudis%2520PhD%25202016%2520Supplementary%2520files.zip |
| Summary: | Although our knowledge on the vast deep-sea biome has increased in recent decades, we still have a poor understanding of the processes regulating deep-sea diversity and assemblage composition, as well as their underlying natural variability in space and time. In the face of unprecedented anthropogenic impact on this environment, addressing this knowledge gap remains of paramount importance. In this thesis I focus on the effect of mesoscale (10s of kilometres) spatial heterogeneity, in the form of abyssal hills and surrounding abyssal plains, on benthic communities and specifically on foraminiferal faunas living at abyssal depths in the northeast Atlantic. ‘Live’ (Rose-Bengal-stained) and dead benthic foraminiferal assemblages, including rarely-studied soft-walled monothalamous species, were analysed based on a total of 16 Megacorer samples (0.25 cm2 surface area, 0-1 sediment horizon, >150 ?m sieve fraction) from five sites within the area of the Porcupine Abyssal Plain Sustained Observatory (PAP-SO, NE Atlantic, ~4850 m water depth). Three sites were located on the tops of small abyssal hills (~200-500 m elevation) and two on the adjacent abyssal plain. The main results of this analysis include the following. (1) Description of new morphotypes of poorly known primitive benthic foraminifera associated with (i.e. sessile on) planktonic foraminiferal shells and mineral grains. Some of these forms were more common on the hills, while others were more common on the plain. (2) Agglutinated foraminifera selected particles of different sizes on the hills compared to the plain, which affected their test morphometry and visual appearance. Distinct hydrodynamic conditions, and consequently distinct sediment granulometric characteristics between the two settings (hills, plain) resulted in foraminifera on the hills having more coarsely agglutinating tests. This information could be useful in palaeoecological interpretations of the fossil record. (3) Live benthic foraminiferal assemblages were significantly influenced by ... |
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