International Journal of Marine Science, 2017, Vol.7, No.7, 59-66
59
Research Article Open Access
Meiofaunal Distribution across the Oxygen Minimum Zone of Continental
Margin, North East Arabian Sea
Z.A. Ansari
1
, Shahin Badesab
1
, R. Singh
1
, Hiroshi Kitazato
2
1 National Institute of Oceanography, Dona Paula Goa 403004, India
2 Japan Agency for Marine-Earth Science and Technology, Natsushima 2-15, Yokosuka, Kanagawa 237-0061, Japan
Corresponding email
International Journal of Marine Science, 2017, Vol.7, No. 7 doi
Received: 3 Jan., 2017
Accepted: 16 Feb., 2017
Published: 6 Mar., 2017
Copyright © 2017
Ansari et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Ansari Z.A., Badesab S., Singh R., and Kitazato H., 2017, Meiofaunal distribution across the oxygen minimum zone of continental margin, north east Arabian
Sea, International Journal of Marine Science, 7(7): 59-66 (doi
Abstract
A quantitative study of metazoan meiofauna across the oxygen minimum zone (OMZ) of continental margin in the N-E
Arabian Sea in the depth range 500-1965 m was carried out in September-November 2008. Bottom water oxygen and sediment
organic carbon showed large variation between stations. The bottom water temperature and salinity was very similar in the area. The
fauna was dominated by nematoda followed by harpacticoid copepoda and polychaeta. Maximum meiofaunal density of 164/10 cm
2
was recorded at St. 1 (500 m) and the lowest density of 25/10 cm²was observed at St. 2 (650 m) which coincided with lowest oxygen
concentration. Total abundance of meiofauna was significantly lower than those reported from other areas. The average density was
high (65/10 cm
2
) in OMZ than in non OMZ (52/10 cm
2
) area. Nematodes were the dominant taxon at every station. The dominance
was particularly significant at those stations having very low oxygen. The meiofaunal density was positively correlated with sediment
organic carbon while oxygen exhibited a negative correlation. Epibenthic Crustacean groups were more in areas of non OMZ having
high oxygen. Vertical distribution revealed consistent reduction in total density and major taxa with increasing depth in sed iment.
Maximum density was recorded in top 0-2 cm layer. Among environmental parameters the availability of food in the form of
sediment carbon appeared to be key factor in controlling meiofauna in study areas.
Keywords
Oxygen minimum zone; Meiofauna; Distribution; Arabian Sea
Introduction
Our understanding of the biological oceanography of the deep Arabian Sea has come largely through systematic
collection of data during different oceanographic cruises (Qasim 1982; Angel, 1984). High surface productivity
results in deposition of high organic carbon and nitrogen at the water-sediment interface (Gage et al., 2000).
Limited sources of water replacement and high microbial activity in north eastern Arabian Sea have produced an
intense and unusually deep oxygen minimum layer. It has supported one of the largest well defined OMZ where
about 285000 km
2
of continental margin in the depth zone100-1500 m seafloor is impacted (Helly and Levin,
2004; Stramma et al., 2008). The high organic carbon and nitrogen in the surficial sediment has helped in the
development of reducing condition at intermediate depths (Cowie, 2005).
To date there are limited studies on marcofauna and meiofauna community distribution on the continental margin
including the OMZ of the Arabian Sea (Cook et al., 2000; Ingole et al., 2010; Jaleel, 2012). In a recent
communication Gage et al. (2000) emphasized the need for better understanding of benthic biology of the deep
Arabian Sea affected by permanent OMZ. The meiofauna have a well defined three dimensional distribution based
on adaptations of their species to occupy the spaces within the sediment up to several centimeters in depth
(Soetaert et al.,
1994). The nematodes among meiofauna particularly tend to be more tolerant than macrofauna to
anoxia (Levin et al., 1991).
In comparison to temperate habitats, the ecology of meiofauna in tropical areas still needs to be widely explored,
particularly in extreme regions. Oxygen minimum zones (OMZ) are stable water bodies of extreme environments
where dissolved oxygen levels fall below 0.5 ml/l (Levin, 2003). We planned this study to update our
understanding of the finer distribution of taxonomic composition, numerical abundance and vertical distribution
