Seabed environmental survey of Angola Blocks 18WAD and 31: analysis of seabed samples
Seabed environmental survey of Angola Blocks 18WAD and 31: analysis of seabed samples
This report details the analysis and interpretation of seabed sample data carried out on behalf of BP
Angola for an environmental survey of Angola Blocks 18 and 31 (bathyal SE Atlantic). Seabed
sampling was undertaken with the NOC Megacorer to produce material for the assessment of
hydrocarbons, heavy metals, particle size, total organic carbon and nitrogen and macrobenthos. Seabed
sampling spanned water depths of 1300-2050m over the Angolan Margin and included sites on the open
continental slope and on and around seabed pockmarks and salt diapirs. Analysis of the resultant data
indicates that many physical / chemical parameters vary systematically with water depth and with
seabed type (background, diapir and pockmark habitats). Contrary to expectation, sediments coarsen
and organic matter (total organic carbon and total nitrogen) increases with depth, this, however, may be
a local rather then regional trend. A number of the sampled diapir and pockmark sites are notable for
possible indicators of fluid flow, elevated total hydrocarbon levels, unusual hydrocarbon compositions
and variant macrobenthos species composition, all potentially indicative of fluid escape from the seabed
(? seep sites). The macrobenthos are highly diverse and likely include a majority of species new to
science. There is a strong trend of increasing biodiversity, particularly species richness, with depth and
some indication that biodiversity is enhanced at diapir sites and somewhat reduced at pockmark sites.
Controls on the species composition of the macrobenthos are undoubtedly complex and include both a
suite of depth varying factors together with local habitat variation, which likely includes the influence of fluid flow.
Should you wish to consult or cite this report please contact the author directly (Brian Bett, bjb@noc.soton.ac.uk, +44 (0)23 80596355).
Angola, Angolan Margin, bathyal, benthos, biodiversity, BP, chemosynthetic communities, continental slope, fluid flow, heavy metals, hydrocarbons, macrobethos, Megacorer, pockmarks, salt
diapirs, SE Atlantic, seabed, sediment particle size, sediments, species diversity, total nitrogen, Total Organic Carbon
National Oceanography Centre
Bett, B.J.
61342990-13be-45ae-9f5c-9540114335d9
Hughes, J.A.
285bf26c-3175-4373-8cfa-449f38b4db30
2 October 2007
Bett, B.J.
61342990-13be-45ae-9f5c-9540114335d9
Hughes, J.A.
285bf26c-3175-4373-8cfa-449f38b4db30
Bett, B.J. and Hughes, J.A.
(2007)
Seabed environmental survey of Angola Blocks 18WAD and 31: analysis of seabed samples
(National Oceanography Centre Southampton Research and Consultancy Report, 30)
Southampton, UK.
National Oceanography Centre
58pp.
Record type:
Monograph
(Project Report)
Abstract
This report details the analysis and interpretation of seabed sample data carried out on behalf of BP
Angola for an environmental survey of Angola Blocks 18 and 31 (bathyal SE Atlantic). Seabed
sampling was undertaken with the NOC Megacorer to produce material for the assessment of
hydrocarbons, heavy metals, particle size, total organic carbon and nitrogen and macrobenthos. Seabed
sampling spanned water depths of 1300-2050m over the Angolan Margin and included sites on the open
continental slope and on and around seabed pockmarks and salt diapirs. Analysis of the resultant data
indicates that many physical / chemical parameters vary systematically with water depth and with
seabed type (background, diapir and pockmark habitats). Contrary to expectation, sediments coarsen
and organic matter (total organic carbon and total nitrogen) increases with depth, this, however, may be
a local rather then regional trend. A number of the sampled diapir and pockmark sites are notable for
possible indicators of fluid flow, elevated total hydrocarbon levels, unusual hydrocarbon compositions
and variant macrobenthos species composition, all potentially indicative of fluid escape from the seabed
(? seep sites). The macrobenthos are highly diverse and likely include a majority of species new to
science. There is a strong trend of increasing biodiversity, particularly species richness, with depth and
some indication that biodiversity is enhanced at diapir sites and somewhat reduced at pockmark sites.
Controls on the species composition of the macrobenthos are undoubtedly complex and include both a
suite of depth varying factors together with local habitat variation, which likely includes the influence of fluid flow.
Should you wish to consult or cite this report please contact the author directly (Brian Bett, bjb@noc.soton.ac.uk, +44 (0)23 80596355).
This record has no associated files available for download.
More information
Published date: 2 October 2007
Additional Information:
Abstract deposited at the request of B.J.Bett. Any request to view the whole document should be directed to him - contact details included in abstract.
Keywords:
Angola, Angolan Margin, bathyal, benthos, biodiversity, BP, chemosynthetic communities, continental slope, fluid flow, heavy metals, hydrocarbons, macrobethos, Megacorer, pockmarks, salt
diapirs, SE Atlantic, seabed, sediment particle size, sediments, species diversity, total nitrogen, Total Organic Carbon
Identifiers
Local EPrints ID: 48603
URI: http://eprints.soton.ac.uk/id/eprint/48603
PURE UUID: 7dae241d-5691-41f1-9cf2-ac8fd7c7c631
Catalogue record
Date deposited: 02 Oct 2007
Last modified: 04 Apr 2024 17:09
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Contributors
Author:
B.J. Bett
Author:
J.A. Hughes
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