http://nopr.niscair.res.in/handle/123456789/4 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/85 Title: A review of the studies on pteropods from the northern Indian Ocean region with a report on the pteropods of Irrawaddy continental shelf off Myanmar (Burma) <br/> <br/>Authors: Panchang, Rajani; Nigam, Rajiv; Riedel, Frank; Janssen, Arie W.; Hla, U Ko Yi <br/> <br/>Abstract: Ever since the Challenger Expedition the Indian Ocean pteropods have been recognized as important constituents of biogenic flux. Initially they were of interest only to biologists or the fishery departments and their distribution was studied only in plankton tow samples. Over the past three decades micropalaeontologists have paid attention to investigate pteropods from water and sediment samples to understand their distribution and ecological significance. Since then substantial work has been reported in the Gulf of Aqaba, Red Sea, northern Arabian Sea, along west coast of India and around the Andaman Nicobar Archipelago. Work has neither been attempted in the Bay of Bengal nor in the northern Andaman Sea. These aragonitic microfossils have proved to be reliable indicators of bathymetry, productivity, upwelling, current circulation, intensity of Aragonite Compensation Depths, Oxygen Minimum Zone and monsoons, thus very useful in palaeoclimatic reconstructions. Works on its counterparts such as foraminifers and ostracods have been reviewed earlier and this is the first time a review of the pteropod studies in the northern Indian Ocean is being attempted, in view of the vast data generated in this region. The pteropod assemblages from two cores collected on the Irrawaddy continental shelf, in the northern Andaman Sea is also reported for the first time. The downcore distribution of pteropods suggests that no significant sea level change has occurred over the past ~1280 Cal yrs. <br/> <br/>Page(s): 384-398 http://nopr.niscair.res.in/handle/123456789/84 Title: Organic matter distribution pattern in Arabian Sea: Palynofacies analysis from the surface sediments off Karwar coast (west coast of India) <br/> <br/>Authors: Prasad, Vandana; Garg, Rahul; Singh, Vartika; Thakur, Biswajit <br/> <br/>Abstract: Central Arabian Sea region, situated off the Karwar coast, is characterized by intense mid depth (~120-1200 m) oxygen minima zone and shows preservation and accumulation of relatively high organic matter content. Palynofacies analysis was carried out with a view to understand the organic matter production, preservation and degradation in the surface sediments of Arabian Sea from 15 m-2750 m depth off Karwar [14.47-14.40 N -70.77-74.25 E transect]. Palynofacies analysis, which involves qualitative and quantitative estimation of terrestrial and marine organic matter is a useful tool to decipher and assess paleoenvironmental changes in various water depth zones from shelf-slope region off the Karwar coast. There is a marked change in the palynofacies characteristics of the organic matter recovered from various depth zones. High SW monsoonal activity over Karwar coast results in increased runoff and nutrient loading in the coastal waters. This enhances primary productivity in the inner shelf region. Organic walled dinoflagellate cysts as important constituent of primary productivity, predominate under such conditions, being converted into Amorphous organic matter (AOM) as a result of degradation under low oxygen environment. Hence, in the present study high AOM is used as proxy for the low oxygen content at sediment-water interface. It also provides evidence of high primary productivity in the photic zone. Study further reveals that terrestrially derived charcoal and woody plant tissue resistant to degradation, are transported to continental slope regions at greater depths. Occurrence of a large proportion of well preserved labile organic matter (exoskeleton fragments of planktonic crustaceans) and AOM in the mid-outer slope surface sediments indicate enhanced primary productivity and high rate of burial efficiency making these areas, characteristic of low oxygen. The study shows that the Karwar coast margin is highly productive as a result of runoff related nutrient loading and is the primary cause for oxygen minima conditions. <br/> <br/>Page(s): 399-406 http://nopr.niscair.res.in/handle/123456789/69 Title: Episodic preservation of pteropods in the eastern Arabian Sea: Monsoonal change, oxygen minimum zone intensity and aragonite compensation depth <br/> <br/>Authors: Singh, A. D. <br/> <br/>Abstract: The preservational record of pteropod shells (aragonite) for the last 30 kyr has been studied in a core (SK17) recovered from the eastern Arabian Sea margin at off Goa coast (depth 840m, lat. 15°15’N, long. 72°44’E). The chronostratigraphy of the core established on the basis of high resolution stable isotope record of a planktic foraminifera (Globigerinoides ruber) and several AMS radiocarbon ages demonstrates millennial scale variation in δ ¹⁸O defining Younger Dryas and Heinrich like Events. Records of absolute abundance of pteropods (1g/dry wt >125 Mu m), abundance ratio of pteropod and planktic foraminifera, aragonite (wt %), organic carbon (OC) (wt %) and CaCO₃ (wt %) show major changes during these isotopic events. Aragonite maxima and higher number of well-preserved pteropod shells, are noticed during cold stadial periods. The study indicates a negative correlation between aragonite and OC % (productivity index). On the other hand, total CaCO₃ content (calcite and aragonite) is positively correlated with the aragonite. The variation patterns of pteropod shells and aragonite content in the sediment core are suggested to be controlled by the preservational conditions associated with the fluctuation in Aragonite Compensation Depth (ACD) and Oxygen Minimum Zone (OMZ) intensity. It is suggested that the high biological productivity during intensified summer monsoons in late Holocene and inter-stadial periods might have resulted in severe oxygen depletion (strong OMZ) leading to shallowing of the ACD. A weak summer monsoon and low productivity condition prevailing during cold stadial periods would have resulted in a weak OMZ and deepening of the ACD. <br/> <br/>Page(s): 378-383 http://nopr.niscair.res.in/handle/123456789/68 Title: Distribution of Ostracoda in marine and marginal marine habitats off Tamil Nadu and adjoining areas, southern east coast of India and Andaman Islands: Environmental implications <br/> <br/>Authors: Hussain, S.M.; Ganesan, P.; Ravi, G.; Mohan, S.P.; Sridhar, S.G.D. <br/> <br/>Abstract: Ostracods successfully inhabit almost all types of aquatic environment, from deep oceans to brackish water lagoons, estuaries and even freshwater streams, lakes, etc. The major controlling factors governing ostracod population and distribution in estuarine environments and continental shelf zones are water temperature, salinity and substrate. In this paper, the distribution and ecology of marine ostracoda in relation to the environmental parameters such as temperature, salinity, dissolved oxygen of the bottom waters, organic matter, and CaCO3, along with the sand-silt-clay ratio of sediments from the inner shelf sediment region off Karikkattukuppam (near Chennai), off Rameswaram, off Tuticorn and Andaman Islands is discussed. Additionally, similar studies on the brackish water ostracods from the Adyar estuary, Pitchavaram mangroves and Tamiraparani estuary have also been presented. The work pertaining to the statistical parameters of ostracoda such as carapace/valve ratio, ornamentation and grain size to infer the environment of the study area, from the Indian region is also discussed. <br/> <br/>Page(s): 369-377