NISCAIR Online Periodicals Repository Community: IJMS Vol.34 [2005]

Evolution of Iskapalli lagoon in Penner delta region, east coast of India—A sedimentological and palynological approach

Mon, 29 Aug 2005 22:58:59 GMT

Title: Evolution of Iskapalli lagoon in Penner delta region, east coast of India—A sedimentological and palynological approach

Authors: Seetharamaia, J; Farooqui, Anjum; Suryabhagavan, K V; Rao, K Nageswara

Abstract: The Holocene evolution of the Iskapalli lagoon has been reconstructed through landform mapping, vibracore lithology and foraminiferal analysis, supplemented by radiocarbon dating. The characteristics: texture, boundary surfaces and the palynological assemblages of the lagoon sediments obtained from two cores indicate three distinct sediment units. The lower part of the core (Unit I) consisting of highly (>85%) oxidized coarse sand mixed with shells, moderate bioturbation, high concentration of Spiniferites, Casuarina, fungal spores and algal cysts together with terrestrial herbaceous taxa and sub-parallel laminations suggests deposition in a sandy river mouth bar environment under strong wave influence. The middle part of the core (Unit II) comprising high silty to sandy mud, and parallel laminations together with Protoperidinium sp., Rhizophora and Avicennia indicated low energy lagoonal environment analogous to the modern lagoonal conditions. The upper part of the cores (Unit III) consisting of well sorted fine sands with abundant terrestrial taxa are considered to be wind blown sands. The oxidized condition of the distributary mouth bar sediments of Unit I and the occurrence of fine sediments of Unit II suggest the lagoon had witnessed at least one cycle of sea level fall and rise during the Late Holocene between 2000 yr BP and 1500 yr BP.

Page(s): 267-273

Full-depths zooplankton composition at two deep sites in the western and central Arabian Sea

Sun, 29 May 2005 22:58:59 GMT

Title: Full-depths zooplankton composition at two deep sites in the western and central Arabian Sea

Authors: Fabian, Heiner; Koppelmann, Rolf; Weikert, Horst

Abstract: The temporal distribution and faunistic composition of zooplankton was studied by means of fine stratified oblique tows with a 1 m² MOCNESS at one station in the western and central Arabian Sea, each. The 333 µm net samples covered the whole water column down to ca. 4000 m, commencing 50 m above bottom, during three monsoon periods: the fall intermonsoon in October 1995, the spring intermonsoon in April 1997 and the NE monsoon in February 1998. Copepods were most abundant at both stations, ostracods ranked next, followed by malacostraceans, and chaetognaths. Total numerical standing stocks varied at the western site between 35 500 and 93 100 no./m² and at the central site between 27 300 and 65 800 no./m². In the epipelagic zone (0-150 m), only calanoid copepods, chaetognaths and gelatinous zooplankton showed an in-phase coupling with the seasonal pattern of primary production, with lowest concentrations during the spring intermonsoon; for all other groups the coupling is not clear. In the mesopelagic zone (150-1050 m), characterized by a pronounced oxygen minimum zone (OMZ), distinct changes in the faunistic composition were found: In the core of the OMZ (O₂ below 0.15 mg/l), the relative abundance of calanoid copepods rose up to 95%, whereas non-calanoid copepods and chaetognaths nearly disappeared. The vertical distributions of selected copepod taxa are discussed in relation to the oxygen profiles. Below the core of the OMZ several groups showed a subsurface peak in abundance. In the bathypelagic zone, below 1050 m, 4-11% of the water column zooplankton standing stock was found.

Page(s): 174-187

Mangrove ecosystems of the Indian Ocean region

Sat, 26 Feb 2005 22:58:59 GMT

Title: Mangrove ecosystems of the Indian Ocean region

Authors: Kathiresan, K.; Rajendran, N.

Abstract: Covering about 47 % of world’s mangrove area, containing 85 % of world’s mangrove species, and occurring in a variety of habitats, the mangrove ecosystem plays a vital role in coastal biodiversity of 30 countries bordering the Indian Ocean. This ecosystem supports a rich species diversity of flora and fauna, but it is facing heavy human pressures and natural stresses, leading to a loss in biodiversity. This calls for urgent measures of conservation and management.

Page(s): 104-113

Coastal processes along the Indian coast - Case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data

Mon, 28 Nov 2005 22:58:59 GMT

Title: Coastal processes along the Indian coast - Case studies based on synergistic use of IRS-P4 OCM and IRS-1C/1D data

Authors: Rajawat, A.S.; Gupta, Mukesh; Pradhan, Yaswant; Thomaskutty, A.V.; Nayak, Shailesh

Abstract: The sequential Suspended Sediment Concentration (SSC) maps were generated using IRS-P4 OCM (Ocean Color Monitor) data for selected tide dominated, wave dominated and deltaic coasts around the Indian subcontinent. Patterns of SSC were studied to understand the sediment dynamics, circulation patterns, fronts and consequent impact on coastal processes. Hitherto, unknown sediment plumes extending for large distance into deep offshore areas could be identified from the major deltaic regions. The high temporal capability of OCM data was extremely useful to understand sediment dynamics in tide-dominated regions of the Gulf of Khambhat, the Gulf of Kachchh and the Hoogli estuary. SSC maps in conjunction with corresponding tide and bathymetry data could be sequenced as per flooding and ebb cycles. Development, formation, shifting nature of shoals and sediment curls during a tide cycle could be studied. It is observed that during the North-East (NE) monsoon suspended sediment influx of the Ganga-Brahmaputra system influences the coastal processes along the continental margins of the Orissa and the Northern Andhra Pradesh along east coast of India. The occurrence of cyclone aids in entrapment of fluvial discharge into the coastal waters, leading to a reduced offshore influx into deeper regions of the Bay of Bengal and high sedimentation near to the coast. Seasonal changes along wave-dominated west coast showed net sediment transport from north to south in the pre-monsoon season and south to north in post-monsoon season. Significant onshore- offshore transport along west coast was also observed. The impact of the regional sediment dynamics on the site-specific local coastal environment was studied by integrating observations derived from OCM and IRS-1C/1D data. The paper concludes the utility of Ocean Color Monitor and IRS-1C/1D data in studying various coastal processes and regional sediment dynamics.

Page(s): 459-472