Little is known about how patterns of deep-sea community structure, but diversity in particular, vary with depth. There are two competing theories in the literature. The first suggests that diversity shows no decline with depth, while the second proposes a more complex pattern in which diversity increases with depth reaching a peak between 2000-3000m. It was decided to test which of these theories most appropriately described polychaete diversity patterns in the Rockall Trough. Spade box core samples were analysed from two transects; one which ran from 400 to 1061m and the second which ran from 1000-2900m, and also from five replicate samples on the floor of the Trough. The processes underlying diversity patterns were also investigated and compared to other studies using a conceptual model. The results of this investigation found that polychaete species richness increased with depth, reaching maximum values between 1000-1400m. Analysis of equitability indicated that the upper slope stations were highly dominated, but gradually became more equitable with increasing depth, although there was considerable variation. There was no evidence to support the role of competition or intra-taxocene predation as structuring processes. However, there was support for the role of disturbance in the form of near-bed currents in structuring upper slope assemblages. In particular, it appeared to be the frequency of high speed currents which was important. Analysis of species distributions indicated that species turnover was highest in areas where the frequency of high speed currents was greatest. By contrast, trophic groups did not show any major trends. Rockall Trough abundances were lower than other studies from the world ocean but no explanation can be offered to explain this. By contrast, species richness and number of species was as high as comparable regions. It was suggested that this maybe related to the disturbance regime in the Trough.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638425 |
| Date | January 1993 |
| Creators | Paterson, G. L. J. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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