Distribution of Recent benthic Ostracoda off Karikkattukuppam (near Chennai), southeast coast of India (original) (raw)
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An investigation to record spatial and seasonal distribution of recent benthic ostracoda was carried out along two transects (East and Northeast) off Rameswaram island of Tamilnadu coast, India. Thirty sediment and bottom water samples were collected during January 2011 and April 2011 and analysed for various physico-chemical and sediment characteristics using standard procedures. The top 4 cm sediment was preserved in 10% formaldehyde and later in the laboratory the live and total population of Ostracoda was determined using the rose Bengal stain technique. Faunal frequencies for benthic ostracods were computed and correlated with physico-chemical and sediment characteristics. The correlation reveals that ostracod frequency has a positive correlation with sandy substrate and negative correlation with clay substrate and OM%. Faunal frequencies increased by 3 times during summer (April 2011) although values of physico-chemical and sediment characteristics do not show considerable variation from January 2011. The east transect is proximal to the coral reef and characterized by sandy substrate in both seasons, supports high populations and therefore is more congenial for ostracod proliferation. Finally, environmental variables have been correlated with those measured three decades ago to understand the causes for variations.
Fourteen surface and two core sediment samples were collected from the backwaters of Cochin, Kerala, southwest coast of India, in order to study the systematics and distribution of Recent Ostracoda. The ostracod taxa were separated from the sediments applying standard micropaleontological techniques. A total of 20 Ostracod species belonging to 17 genera and 8 families were identified. Sediment parameters such as CaCO3, organic matter and sand-silt-clay ratio were estimated for the surface as well as core samples in order to determine the relationship between substrate and Ostracoda populations, and to evaluate the favoured substrate of dominant species populations. The down core distribution of sediment parameters and ostracod assemblages is presented. Based on this data we determine that ostracods favour silty-sandy substrate environments. The rate of sedimentation was determined based on the ratio between the carapace and open valves of Ostracoda. The benthic ostracod fauna recorded is characteristic of a tropical, brackish to epi-neritic environment and few warm, shallow marine species occur in the backwaters of Cochin, may be due to the tidal influence.
2007
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, ornamenta...
RECENT OSTRACOD BIODIVERSITY FROM SHELF TO SLOPE SEDIMENTS OF GULF OF MANNAR, INDIA
The present study has been focused to create the baseline data for the distribution and biodiversity of Ostracoda from the continental shelf to slope sediments of Gulf of Mannar. For the purpose, 5 short core samples were collected through multi-corer, ranged in water depth from 58 m to 1887 m (shallow to deep-marine water) during Cruise SSD-004 (ORV Sindhu Sadhana). In which, a total of 4355 ostracod specimens were recovered, belonging to 82 species and 51 genera. Of these, 14 species were recorded for the first time from the Indian waters. Bathymetric distribution of Ostracoda in all the five multi-core samples are studied, in which Propontocypris bengalensis, a species that is dominantly present in shallow water region (MC-8). Species of Krithe recorded only in deeper water regions (MC-2 and MC-60). Xestoleberis sp. and Paracypris sp. are the only species which were present from the continental shelf to slope sediments of Gulf of Mannar. The faunal carapaces are fresh, shiny, and not pyritised. The ornamentation on the carapaces changes gradually in accordance with the sediments that grades from coarse to fine towards the deeper water and the population of ostracod also varies from shallow to deeper water sediments. Core-wise distributions of ostracods species, ecological implications and species diversity have also been discussed.
Ostracod biodiversity from shelf to slope oceanic conditions, off central Bay of Bengal, India
Thirty seven surface sediment samples collected through a multi-corer in seven transects of ORV Sagar Kanya, SK 308 Leg-1 from off central Bay of Bengal (shelf to slope environment) were analysed for living and dead Ostracoda. The samples, which ranged in water depth from ~29 m to 2540 m, yielded a total of 46 species belonging to 32 genera. The ostracod fauna of the Bay of Bengal exhibit a depth-related distribution that is controlled by substrate and hydrographic conditions. Sandy substrates of shallow water depth (~28 m) are characterized by Propontocypris sp. and Cytherelloidea malaccaensis. These species are replaced by Neonesidea cracenticlavula and Bairdoppilata paraalcyonicola in high population, which shows positive linear correlation with salinity, temperature and Total Calcium Carbonate (TCC) in the outer shelf ~55–73 m. Paijenborchella sp. dominates at ~763 m in the bathypelagic zone, giving way to Parakrithella sp. at greater depths of ~2540 m on soft-bottom substrates. The fauna represents an interesting mixture of displaced species and others known from bathyal and abyssal depths in the Bay of Bengal, including some pandemic deep sea species. The ostracod faunal diversity is higher in shallower water than in the deeper water, which may be due to the optimum temperature, pH, salinity and sub-strate. The fauna are comprised of three associations (Shelf/Upper Slope; Slope; Lower Slope/Abyss). A marked faunal turnover occurs at the outer-shelf. Factor Analysis was performed to determine the correlation of water and sediment parameters with the ostracod species. This study provides a detailed account of bathymetry and ostracod biodiversity recorded in the study area.
Seasonal observation on physico-chemical parameters were correlated with population of ostracoda in southern region off Rameswaram, Gulf of Mannar, Ramanathapuram district, Tamil Nadu, southeast coast of India, by collecting bottom sediment and water samples in the inner shelf region. 11 samples were collected every season, for four different seasons, namely, northeast monsoon (October 2010), winter (January 2011), summer (April 2011) and southwest monsoon (July 2011) seasons. Spatial and seasonal variation in physico-chemical and hydrographic parameters and sampling stations having higher population of ostracoda were critically analysed with the observed parameters. Highest population of ostracoda was recorded during summer followed by southwest monsoon, northeast monsoon and winter season. Cluster analysis reveal that station 9 falls in all seasons under favourable location, during different seasons and is having the most congenial environment for ostracoda to thrive. Depth, pH, dissolved oxygen, salinity, EC, TDS, nitrite and silica show positive correlation, and turbidity, nitrate and phosphate show negative correlation with total population of ostracoda.
A total of twenty-two surface sediment samples collected through SSK-35 from the coastal region along the northwestern part of the Bay of Bengal were provided to carry out a preliminary study on the distribution of ostracoda. The ostracoda taxa were separated from the sediments applying standard micropaleontolgical techniques, their distribution in individual sample examined and environmental interpretation made. Twenty one species belonging to 18 genera have been identi ed. Out of these Echinocythereis species, Cytherelloidea leroyi and Keijia demissa are well represented in the samples. From the occurrence and distribution of the ostracod assemblage, it is inferred that the sediments are deposited in a tropical, shallow, inner shelf environment. In the present work, the ratio between the carapaces and open valves has been taken into consideration for determining the comparative rate of sedimentation in the study area. Out of the twenty two samples, as many as 607 ostracod shells were recovered. Among these, 90% specimens were open valves and the remaining 10% were complete carapace. The distribution of carapaces and open valves in the samples of the Bay of Bengal shows that comparatively a slow rate of sedimentation may have prevailed in the locations of study areas of the Bay, probably under normal oxygenated environmental conditions. The ostracod specimens are white to light yellow in colour with a couple of predated species and no pyrite deposit in the ostracoda shells.
A total of twenty-two surface sediment samples collected through SSK-35 from the coastal region along the northwestern part of the Bay of Bengal were provided to carry out a preliminary study on the distribution of ostracoda. The ostracoda taxa were separated from the sediments applying standard micropaleontolgical techniques, their distribution in individual sample examined and environmental interpretation made. Twenty one species belonging to 18 genera have been identi ed. Out of these Echinocythereis species, Cytherelloidea leroyi and Keijia demissa are well represented in the samples. From the occurrence and distribution of the ostracod assemblage, it is inferred that the sediments are deposited in a tropical, shallow, inner shelf environment. In the present work, the ratio between the carapaces and open valves has been taken into consideration for determining the comparative rate of sedimentation in the study area. Out of the twenty two samples, as many as 607 ostracod shells were recovered. Among these, 90% specimens were open valves and the remaining 10% were complete carapace. The distribution of carapaces and open valves in the samples of the Bay of Bengal shows that comparatively a slow rate of sedimentation may have prevailed in the locations of study areas of the Bay, probably under normal oxygenated environmental conditions. The ostracod specimens are white to light yellow in colour with a couple of predated species and no pyrite deposit in the ostracoda shells.
A preliminary study on the marine Ostracoda is carried out from a shallow short core of length 20 cm collected from the region of Bay of Bengal, off the coast of Ongole using a multicorer during the ORV Sagar Kanya cruise (SK-308 Leg 1), at a water depth of 47 metres. The core is further sampled at an interval of 1cm and thus, a total of 20 samples were obtained and are subjected to standard micropaleontological and sedimentological analyses. The classification by Hartmann and Puri (1974) is followed through which 41 ostracod taxa belonging to 33 genera of the order Podocopida have been identified, from which 2 species belong to suborder Platycopa and the remaining to suborder Podocopa. Ostracod assemblage recorded is characteristic of shallow insitu marine, inner shelf and tropical in nature. Sedimentological parameters such as CaCO 3, Organic matter and sand-silt-clay ratios were estimated and their down core distribution is discussed. Granulometric studies reveal that fine grained silt and clay are more than sand in the core sample reflecting on low energy condition of sediment deposition. Ostracods from the area are larger in size, ornamented and well preserved. Approximate averages of only 42 specimens are found per 10 grams. The ratio between the carapaces and open valves has been taken into consideration for determining the relative rate of sedimentation and it has been identified as slower rate of sedimentation prevailing in the area.