Deep Sea Research Part I: Oceanographic Research Papers
NoteBacterial and zooplankton distribution in deep waters of the Arabian Sea
Introduction
Carbon dioxide is transformed into organic carbon via photosynthetic activity by phytoplankton in the euphotic zone of the oceans. Phytoplankton is consumed by herbivorous organisms that are fed upon by omnivorous and carnivorous animals. Ungrazed cells, viral lysis, transparent exopolymer particles (TEP), carcasses and fecal material produce particulate organic carbon (POC). This material is eaten by detritivorous zooplankton, is remineralized by bacterial activity, or sinks to greater depths. POC is partly transformed into dissolved organic carbon (DOC) by metabolic activity and fuels the microbial loop (see Williams, 1990; Ducklow, 2000).
Information on the vertical distribution of free-living bacteria and their contribution to carbon flux to bathypelagic depths is sparse (see Nagata et al., 2000; Hansell and Ducklow, 2003), as are papers that deal with comparisons of bacterial distributions and other planktonic groups to describe interactions of the biota in the ocean's interior. Patterson et al. (1993) and Tanaka and Rassoulzadegan (2002) investigated the distribution of bacteria and protozoa down to bathypelagic depths of the NE Atlantic and the NW Mediterranean, respectively, and Raghukumar et al. (2001) did so in the Arabian Sea. Yamaguchi et al. (2002) investigated concomitantly the deep distribution of bacterio-, phyto-, protozoo- and metazooplankton. Their study was done at sites of different productivity in the Pacific Ocean. Knowledge about the abundance and vertical distribution of functional groups within the plankton community will give insights into their contribution to carbon utilization in the sea.
Our paper will describe the vertical distribution of free-living bacteria and zooplankton at two deep sites in the Arabian Sea. We will show that bacterial biomass is higher than mesozooplankton biomass in the deep-sea and that the vertical distribution of bacteria and mesozooplankton is influenced by a very pronounced zone of permanent oxygen deficiency between the lower boundary of the euphotic zone and more than 1000 m depth that extends over large areas of the Arabian Sea (Sewell and Fage, 1948; Olson et al., 1993).
Section snippets
Material and methods
Water bottle and net samples were taken at two sites in the Arabian Sea (Fig. 1) to determine the abundance and distribution of bacteria and mesozooplankton during Sonne cruise 129 (Pfannkuche and Utecht, 1999): at the Western and Central Arabian Sea Sediment Trap stations WAST (16°15′N, 60°20′E, water depth 4050 m) and CAST (14°30′N, 64°30′E, water depth 3950 m). Samples were taken at the end of the NE monsoon, when enhanced production in the northern part of the basin occurs (Sarangi et al.,
Abiotic parameters
Temperature, salinity and oxygen content (Fig. 2) were highest in the upper 50 m of the water column at WAST (T=25.9 °C, S=36.3–36.4, O2=170 μmol l−1) and CAST (T=26.8–26.9 °C, S=36.4–36.5, O2=153–163 μmol O2 l−1). Between 50 and 200 m all parameters decreased sharply. Below 170 m at WAST and 130 m at CAST, a marked oxygen minimum zone (OMZ) extended to 930 m at WAST and 850 m at CAST, with concentrations of less than 6 μmol O2 l−1. At greater depths, the increase of oxygen to 153 μmol O2 l−1 at 4000 m at WAST was
Discussion
Information about concomitantly taken samples of bacteria and zooplankton is sparse for the deep-sea (see also Yamaguchi et al., 2002) and, hence, the knowledge about the importance of these biotic groups in the deep-sea ecosystem is limited. This research note contributes to the knowledge about the distribution and ecological role of these groups in the deep ocean's interior. We will outline possible interactions of zooplankton and bacteria with particulate and dissolved organic material
Acknowledgements
This study is part of the German JGOFS Indian Ocean study funded by Grants of the German Ministry of Education and Research (FKZ's 03F0137A, 03F0183A, 03F0241A, TP 14) to H. Weikert. Our thanks goes as well to the ship staff and our colleagues on board of the R.V. Sonne cruise So129 for their skilful help and assistance. Thanks are due to three anonymous reviewers for helpful comments on the manuscript. Chlorophyll data were generously provided by the SeaWiFs project, NASA/Goddard Space and
References (34)
- et al.
Microbial activity and particulate matter in the benthic nepheloid layer (BNL) of the deep Arabian Sea
Deep-Sea Research II
(2000) - et al.
The contribution of microorganisms to particulate carbon and nitrogen in surface waters of the Sargasso Sea near Bermuda
Deep-Sea Research I
(1995) - et al.
Bottom-up and top-down control of bacterioplankton from eutrophic to oligotrophic sites in the tropical northeastern Ocean
Deep-Sea Research I
(1996) - et al.
Microbial food web structure in the Arabian Sea: a US JGOFS study
Deep-Sea Research II
(2000) - et al.
Spatial and temporal variations of total organic carbon in the Arabian Sea
Deep-Sea Research II
(1998) - et al.
Distribution, partitioning and fluxes of dissolved and particulate organic C, N and P in the eastern North Pacific and Southern Oceans
Deep-Sea Research I
(2000) - et al.
Maintenance of the low-oxygen layer in the central Arabian Sea
Deep-Sea Research II
(1993) - et al.
Bacterial biomass and activity in the deep waters of the eastern Atlantic—evidence of a barophilic community
Deep-Sea Research I
(1997) - et al.
Full-depth profile (0-2000 m) of bacteria, heterotrophic nannoflagellates and ciliates in the NW Mediterranean Sea: vertical partitioning of microbial trophic structures
Deep-Sea Research II
(2002) - et al.
Chemoautotrophic activity and nitrification in the oxygen minimum zone off Peru
Deep-Sea Research I
(1989)
Structure and size distribution of plankton communities down to the greater depths in the western North Pacific Ocean
Deep-Sea Research II
Direct sampling and in situ observation of a persistent copepod aggregation in the mesopelagic zone of the Santa Barbara Basin
Marine Biology
Low variability in planktonic and micronektonic populations at 1,000 m depth in the vicinity of 42°N, 17°W; evidence against diel migratory behavior in the majority of species
Biological Oceanography
Life at stable oxygen levels: adaptations of animals to oceanic oxygen minimum layers
Journal of Experimental Biology
Bacterial production and biomass in the oceans
Zooplankton composition at two deep stations in the western and central Arabian Sea
Indian Journal of Marine Sciences
Direct determination of carbon and nitrogen contents of natural bacterial assemblages in marine environments
Applied and Environmental Microbiology
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