Figure 7 - uploaded by Dr. Sonia Munir
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Photographs of Collosphera and Siphonosphera species of Collodaria (a-o) in the Eastern Indian Ocean. (a,b) Siphonosphaera magnisphaera; (c,f) Siphonosphaera polysiphonia; (g,h) Siphonosphaera socialis; (j) and (k) Solenosphaera zanguebarica; (l) Collosphaera macropora; (m) Collosphaera tuberosa; (n,o) Collosphaera huxleyi. Scale bars: (b,h) 50 µm, (e) 10 µm, (f,i-o) 20 µm.
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The plankton radiolarian community was investigated in the spring season during the
two-month cruise ‘Shiyan1‘ (10 April–13 May 2014) in the Eastern Indian Ocean. This is the first comprehensive plankton tow study to be carried out from 44 sampling stations across the entire area (80.00°–96.10° E, 10.08° N–6.00° S) of the Eastern Indian Ocean. The...
Citations
... Planktonic samples in the euphotic zone of the Eastern Indian ocean constituted a diverse population of diatoms [39], tintinnids [40], and radiolarians [41] from the study area 10 • N-6 • S. Compared to previous studies by Martinez [8], we have undertaken the first detailed ecological studies of foraminifera to community structure analysis, diversity, and carbon biomass estimation in the euphotic zone of the Eastern Indian Ocean. In the present study, the sampling net (20 µm mesh) was used to collect concentrated plankton samples which contain not only microzooplankton but also phytoplankton and organic matter [33]. ...
Distribution and carbon biomass of planktonic foraminifera were investigated from the euphotic zone of the Eastern Indian Ocean during a two-month cruise, ‘Shiyan I’ (10 April–13 May 2014). Foraminifera species were collected through plankton net sampling at 44 locations (80.00°–96.10° E, 10.08° N–6.00° S). The temperature (°C) ranged between 12.82 and 31.8 °C, the salinity ranged between 32.5 and 35.5, and chlorophyll-a concentrations ranged between 0.005 µg/L and 0.89 µg/L. A total of 20 taxa were identified based on the spherical chamber shell, spines, and a final whorl which were examined under light microscopy and scanning electron microscopy. Dominant species that were characterized by the high dominant index Y > 0.14–0.46 were Globigerina bulloides, Globigerinoides ruber white, Globigerinella siphonifera, Turborotalita quinqueloba, and Globigerinella calida, contributing to the community up to 86%. The shell size of collected taxa was from 51 to 508 μm and the total carbon biomass was estimated to be between 0.062 µg C m–3 and 26.52 µg C m–3. The high carbon biomass was recorded at two stations in the equator zone. Due to its large size, Globorotalia menardii had total carbon biomass of 3.9 µg C m–3, followed by G. calida 0.68 µg C m−3, Trilobatus sacculifer 0.38 µg C m–3, Orbulina universa 0.56 µg C m–3, and G. ruber white 0.22 µg C m–3, respectively. The Pearson correlation analysis showed that the temperature and chlorophyll-a were two explanatory environmental variables that were found to be highly significant (p < 0.05) and that triggered the distribution and abundance of dominant foraminifera species in the study region. Overall, high abundances and carbon biomass were derived from the euphotic zone and equatorial region of the Eastern Indian Ocean.
... They found that highest abundances were south of the equator and were mainly driven by silicate levels. Another study in a cold core eddy close to 110 • E and at 31 • S, found small phytoplankton dominated as in a typical oligotrophic system, but these were grazed predominantly by ciliates, and radiolarians and foraminifera were sparse (Munir et al., 2020;Paterson et al., 2007). ...
The large, tropical oligotrophic gyres of the world's oceans are understood to be relatively unproductive, with low phytoplankton and zooplankton biomass, and inefficient food webs, although data are scarce. Here we investigate changes in the zooplankton assemblage along a 15 °C temperature gradient from 20 stations on the 110°E transect as part of the second International Indian Ocean Expedition. To ensure that we reflect most of the zooplankton biodiversity, we used a 100 μm mesh net to capture the small copepod and microzooplankton components that are important and often overlooked in tropical systems. Further, to obtain a synoptic view, we towed the Continuous Plankton Recorder between stations across 30° of latitude. We found that copepod assemblages clustered into four groups, with the most distinct being at the highest latitudes south of the sub-tropical Front. As the ocean temperature increased from south to north along the transect, zooplankton abundance and diversity also increased. The dominant copepod species changed accordingly and were predominantly those with the ability and/or preference to selectively feed on microzooplankton. Although copepods were the most abundant taxon, the proportion of microzooplankton, particularly, mixotrophic Rhizaria, was consistently high. Thus, our study found a highly mixotrophic system supporting secondary production in the oligotrophic Indian Ocean.
... Often they are found in large numbers, and in some cases their total number is simply colossal: up to 16000-20000 colonies per m 3 [19]. Cosmopolitan Collodarii Siphonosphaera polysiphonia and Sphaerozoum punctatum, which are the dominant species in the equatorial waters of the Eastern Indian Ocean in the depth range of 0 to 200 m, had an abundance of 661 ind./m 3 and 5500 ind./m 3 , respectively [57,58]; and in the photic surface layer in the low-latitude zone of the Central Pacific, the density of their populations ranged from 30 to 20000 colonies per m 3 [36]. ...
The theoretical and practical significance of the pioneering discovery of colonial radiolarians Siphonosphaera yamalica Vishnevskaya et Amon from the family Collosphaeridae in the Early Volgian radi-olarian assemblage from the Bazhenov horizon of the South Tambey borehole of Yamal Peninsula (Upper Jurassic, Tithonian, Arctic zone of Western Siberia) is considered. The time of the occurrence of the genus Siphonosphaera is correlated to the Tithonian (Late Jurassic), and the sequences of the stages in the appearance of new representatives of the genus are given. The bionomic characteristics Siphonosphaera allow us to conclude that the water area of the Yamal region was a pelagial of the open ocean, with normal salinity and warm surface waters.
Siliceous planktonic species of the phyla Retaria and Cercozoa were investigated from the surface to a 200 m depth around the eastern Indian Ocean (80.00°–96.10° E, 10.08° N–6.00° S) during a 2-month cruise (10 April–13 May 2014). These species are commonly referred to as Radiolarians and are found in all of the world’s oceans; however, this is a detailed investigation of the species’ diversity in the eastern Indian Ocean. Samples were collected from the eastern Indian Ocean using a plankton towing net during a vertical haul from 44 sampling stations, which resulted in 168 taxa, including 60 species that were newly recorded in the study area. The main purpose of this work was to identify members of the phyla Retaria and Cercozoa and their distribution in the eastern Indian Ocean. The species’ morphology, identification, notes, and new geographical records are briefly described.
