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Large organic-walled Protista (Gromia) in the Arabian Sea: Density, diversity, distribution and ecology

Large organic-walled Protista (Gromia) in the Arabian Sea: Density, diversity, distribution and ecology
Large organic-walled Protista (Gromia) in the Arabian Sea: Density, diversity, distribution and ecology
The genus Gromia includes large marine protists (‘gromiids’) with filose pseudopodia and sack-like organic tests. The first deep-water species were discovered in the 1990s on the Oman Margin of the Arabian Sea and subsequently found on the Pakistan Margin. We present a survey of gromiids in samples collected off Oman in 2002 and off Pakistan in 2003. In addition to the two species (Gromia sphaerica and Gromia pyriformis) already described from this area, at least eight undescribed gromiid species were present. Sausage shaped, grape shaped and spherical morphotypes were represented among this material. On the Oman Margin, gromiids occurred in densities up to several thousand individuals m?2 at 1400 and 1700 m but were much less common at 1100 and 2000 m. Apart from G. pyriformis, which was fairly common (several hundred individuals m?2) at 1000 m, gromiids were uncommon in core samples taken off Pakistan, with 11 indiv. m?2 at 1200 m and 19 indiv. m?2 at 1850 m. On both margins, these protists occurred at depths >1000 m where bottom-water oxygen concentrations exceeded 0.2 ml l?1 (=8.92 ?M l?1) land sediments were fully bioturbated and oxidised. However, they were not observed at similar oxygen levels above the OMZ. Most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria. We conclude that these large protists may play an important ecological role in the bathyal Arabian Sea, particularly in carbon cycling but also in structuring the surficial sediments. In addition, their tests, particularly those of G. sphaerica, provide substrates for attached Foraminifera.
Protozoa, Gromiids, Deep sea, Bathyal, Arabian Sea, Oxygen minimum zone
0967-0645
422-433
Gooday, A.J.
d9331d67-d518-4cfb-baed-9df3333b05b9
Aranda da Silva, A.
72acff95-3c27-4084-bb29-68183e74d5a1
Gooday, A.J.
d9331d67-d518-4cfb-baed-9df3333b05b9
Aranda da Silva, A.
72acff95-3c27-4084-bb29-68183e74d5a1

Gooday, A.J. and Aranda da Silva, A. (2009) Large organic-walled Protista (Gromia) in the Arabian Sea: Density, diversity, distribution and ecology. Deep Sea Research Part II: Topical Studies in Oceanography, 56 (6-7), 422-433. (doi:10.1016/j.dsr2.2008.12.027).

Record type: Article

Abstract

The genus Gromia includes large marine protists (‘gromiids’) with filose pseudopodia and sack-like organic tests. The first deep-water species were discovered in the 1990s on the Oman Margin of the Arabian Sea and subsequently found on the Pakistan Margin. We present a survey of gromiids in samples collected off Oman in 2002 and off Pakistan in 2003. In addition to the two species (Gromia sphaerica and Gromia pyriformis) already described from this area, at least eight undescribed gromiid species were present. Sausage shaped, grape shaped and spherical morphotypes were represented among this material. On the Oman Margin, gromiids occurred in densities up to several thousand individuals m?2 at 1400 and 1700 m but were much less common at 1100 and 2000 m. Apart from G. pyriformis, which was fairly common (several hundred individuals m?2) at 1000 m, gromiids were uncommon in core samples taken off Pakistan, with 11 indiv. m?2 at 1200 m and 19 indiv. m?2 at 1850 m. On both margins, these protists occurred at depths >1000 m where bottom-water oxygen concentrations exceeded 0.2 ml l?1 (=8.92 ?M l?1) land sediments were fully bioturbated and oxidised. However, they were not observed at similar oxygen levels above the OMZ. Most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria. We conclude that these large protists may play an important ecological role in the bathyal Arabian Sea, particularly in carbon cycling but also in structuring the surficial sediments. In addition, their tests, particularly those of G. sphaerica, provide substrates for attached Foraminifera.

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Published date: March 2009
Keywords: Protozoa, Gromiids, Deep sea, Bathyal, Arabian Sea, Oxygen minimum zone

Identifiers

Local EPrints ID: 66592
URI: http://eprints.soton.ac.uk/id/eprint/66592
ISSN: 0967-0645
PURE UUID: 9a5a1048-d053-47a7-b714-aa854a9f6d44

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Date deposited: 30 Jun 2009
Last modified: 13 Mar 2024 18:26

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Contributors

Author: A.J. Gooday
Author: A. Aranda da Silva

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