Current Science

Arvind Singh ¹, R. Ramesh ², Anna Godhe ¹

Affiliations
1 Department of Biological and Environmental Sciences, University of Gothenburg, 405 30 Goteborg, SE
2 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, IN

Abstract

Phytoplankton are key components in primary production and their growth is determined mainly by the availability of nitrogen-nutrients in the ocean. The paradigm that phytoplankton prefer ammonium over nitrate when both substrates are present has been tested using ¹⁵N-labelled tracers on cultured diatoms and dinoflagellates isolated from two widespread geographical areas - the Baltic Sea and the Arabian Sea. We found contrary to the paradigm that both taxa preferred nitrate over ammonium and a significant within-species variation in N assimilation. Carbon uptake rates in the same experiments were estimated using ¹³C-labelled tracer.

Keywords

Carbon, Dinoflagellate, Diatom Species, Nitrogen, Stable Isotopes.

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Satya Prakash ¹, R. Ramesh ¹, M. S. Sheshshayee ², Rahul Mohan ³, M. Sudhakar ³

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Department of Crop Physiology, University of Agricultural Sciences, Bengaluru 560 065, IN
3 National Centre for Antarctic and Ocean Research, Vasco-da-Gama, Goa 403 804, IN

Abstract

We report data on nitrate, ammonium and urea uptake rates from the Equatorial and Southern Indian Oceans. Productivity (0.81-2.23 mmol Nm^-2 d^-1) over the Equatorial Indian Ocean was low, but the f-ratio (0.13-0.45) was relatively high. In the Southern Indian Ocean total N-uptake rate varied from 1.7 to 12.3 mmol Nm^-2 d^-1; it was higher in the Antarctic coast (69°S) and lower over most of the Southern Ocean, the lowest being at 58°S. The f-ratio also showed significant spatial variation, but was higher compared to values at the Equatorial Indian Ocean. The mean f-ratio in the Southern Indian Ocean was 0.50. The nitrate-specific uptake rates and f-ratios appear to have increased significantly in the recent past relative to earlier estimates. While productivity in the Southern Ocean is comparable to that in the Equatorial Indian Ocean, higher f-ratios in the former underscore its importance in the uptake of CO₂.

Keywords

Carbon Sequestration, f-Ratio, Nitrogenuptake, Primary Productivity, Southern Ocean.

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Trina Bose ¹, Supriyo Chakraborty ¹, Hemant Borgaonkar ¹, Saikat Sengupta ¹, R. Ramesh ²

Affiliations
1 Indian Institute of Tropical Meteorology, Pune 411 008, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN

Abstract

We study the applicability of the Farquhar model for carbon isotopic discrimination (change in carbon iso-topic composition from air CO₂ to tree-ring cellulose) in C₃ plants to trees growing in the field. Two new carbon isotope datasets from Himalayan conifers with published data from another eight sites across the world show disparate trends in the plot of carbon iso-tope discrimination versus atmospheric carbon dioxide concentration, in contrast to the model prediction of absence of any trend. This is because the model assumes that the tree adjusts its stomatal conductance for water-use efficiency to maintain a constant ratio of carbon dioxide concentrations inside and outside the leaf and treats the diffusive and biochemical fraction-ation factors as constants. By introducing a simple lin-ear dependence of these fractionation factors with ambient temperature and humidity, we have enhanced the applicability of the model to naturally growing trees. Further, despite the disparate trends exhibited by the 10 trees, we show using the inverse modelling that it is possible to derive a unique record of past atmospheric CO₂ concentrations using tree cellulose δ¹³C data. The reconstructions also replicate the summer pCO₂ gradient from tropics to mid-latitudes. We also discuss the merits and demerits of the model, and compare the model-derived pCO₂ with that of the ice core-based records from Law Dome.

Keywords

Atmospheric Carbon Dioxide, Carbon Iso-Tope, Cellulose, Climate Change, Tree Ring.

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R. Ramesh ¹, R. S. Robin ¹, R. Purvaja ¹

Affiliations
1 National Centre for Sustainable Coastal Management, Ministry of Environment, Forests and Climate Change, Anna University Campus, Chennai 600 025, IN

Abstract

The biogeochemical cycles of phosphorus in rivers are intimately linked to the processes that occur in terrestrial ecosystems. Riverine networks hold a crucial role in the transfer of nutrients from the land and atmosphere to the coastal oceans and often act as pool for numerous inorganic and organic compounds. Biogeochemical transformation of elements in river network is extensively influenced by catchment alteration and anthropogenic inputs. By means of the rising consciousness of human impact on the excellence of rivers, emphasis is given on rivers, as an ecosystem by itself and also on the river-coast continuum. In this study, the major forcing functions that affect the riverine composition of phosphorus have been examined, in Indian context. An attempt has been made to study and inventorize phosphorus flux from major Indian rivers. Relatively high concentrations of dissolved PO^3-₄ (dissolved inorganic phosphorus - DIP) are observed in few of the Indian rivers, which may be due to modifications in river catchment. The flow of DIP and particulate inorganic phosphorus to the coastal ocean from Indian rivers is estimated to be about 190 x 10³ tonnes year^-1 and 1367 x 10³ tonnes year^-1 respectively. Suspended load is significant in Indian rivers and its cumulative flux is in the order of 1450 x 10⁶ tonnes year^-1. The DIP concentration in the Indian rivers is more than twice the concentration observed for the other rivers in the world. Such increased nutrient input into the riverine system reflects the imbalances and alterations in terrestrial sources. Thus, the quantity and quality of nutrient input to the rivers need to be monitored to cope with the existing and future climatic and environmental changes.

Keywords

Biogeochemical Processes, Indian Rivers, Nutrient Fluxes, Phosphorus, Water Quality.

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Shesdev Patro ¹, P. Krishnan ¹, M. Gopi ¹, S. Raja ¹, C. R. Sreeraj ¹, Purvaja Ramachandran ¹, R. Ramesh ¹

Affiliations
1 National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Koodal Building, Anna University Campus, Chennai 600 025, IN

Abstract

No Abstract.

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M. Baskaran ¹, R. Ramesh ²

Affiliations
1 Department of Geology, Wayne State University, Detroit, MI-48202, US
2 Department of Earth and Planetary Sciences, National Institute of Science Education and Research, Bhubaneswar 752 050, IN

Abstract

The demise of B. L. K. Somayajulu, an illustrious nuclear geochemist, brings great sadness to the community of geologists, geochemists and oceanographers in India and elsewhere.

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S. Ramesh ¹, G. A. Ramadass ¹, V. Doss Prakash ¹, C. S. Sandhya ¹, R. Ramesh ¹, D. Sathianarayanan ¹, N. V. Vinithkumar ²

Affiliations
1 National Institute of Ocean Technology (NIOT), Ministry of Earth Sciences, Government of India, Chennai 600 100, IN
2 Andaman and Nicobar Centre for Ocean Science and Technology, NIOT, Port Blair 744 103, IN

Abstract

Coral reef biodiversity in South Andaman Islands, India was studied using indigenously developed remotely operated underwater vehicle, PROVe. The vehicle was manoeuvred in coral reef habitats using underwater navigational aids to record faunal assemblages along with underwater spatio-temporal spectral irradiance characteristics coupled with surface radiance, water temperature, salinity and underwater visuals by high-definition camera devices. PROVe-based observations and the outcome from scientific payloads indicated that it will be a new additional tool for the Indian scientific community to map coral reef habitats, correlate and validate the satellite-derived parameters to understand coral reef health.

Keywords

Coral Reef, Driving Parameters, Remotely Operated Vehicle, Spectral Irradiance.

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C. R. Sreeraj ¹, K. R. Abhilash ¹, V. Deepak Samuel ¹, P. Krishnan ¹, R. Purvaja ¹, R. Ramesh ¹

Affiliations
1 National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Anna University Campus, Chennai 600 025, IN

Abstract

Rhodoliths are nodular form of marine free-living, non-geniculate, crustose coralline red algae, resembling the corals. The communities, in which they dominate are referred to as ‘rhodolith beds’, ‘rhodolites’ or ‘maerl’. Rhodoliths assume different sizes, shapes and forms (small thalli-like, twig-like, large round shaped, branching/unbranching, etc.) based on different factors such as water motion, bioturbation, grazing, fouling, bleaching, etc..

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P. Krishnan ¹, R. Purvaja ¹, C. R. Sreeraj ¹, R. Raghuraman ¹, R. S. Robin ¹, K. R. Abhilash ¹, R. S. Mahendra ², A. Anand ³, M. Gopi ¹, P. C. Mohanty ², K. Venkataraman ¹, R. Ramesh ¹

Affiliations
1 National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Anna University Campus, Chennai 600 025, IN
2 Indian National Centre for Ocean Information Services, Hyderabad 500 090, IN
3 Regional Remote Sensing Centre, Indian Space Research Organisation, Nagpur 440 010, IN

Abstract

The status of reefs in Palk Bay and the Gulf of Mannar was studied during April–May 2016 following a bleach alert, as the sea surface temperature recorded a sudden increase from 30.5°C to 34.0°C in Gulf of Mannar. About 71.48% ± 8.9% of the corals in Palk Bay and 46.04% ± 3.78% in Thoothukkudi group of Islands in Gulf of Mannar were found bleached, showing a clearly decreasing trend from north to south, which could be attributed to the corresponding pattern in intensity of SST recorded in the study sites. Observations of bleaching patterns among different life-forms showed 68% of the bleached corals were massive forms. It was observed that 22 out of the 26 massive forms were bleached, while the Acropora corymbose (ACC), digitate (ACD) and encrusting coral (CE) forms were not bleached in any of the study sites in Palk Bay and Gulf of Mannar. The study suggests that the ACC, ACD and CE forms have adapted to thermal stress, subsequent to the earlier mass bleaching events. The study highlights the need for understanding the molecular mechanism of the association between corals and the symbiotic algae, for further understanding on coral bleaching in Indian waters.

Keywords

Adaptive Coral Bleaching, Gulf of Mannar, Palk Bay.

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G. A. Ramadass ¹, S. Ramesh ¹, N. Vedachalam ¹, A. N. Subramanian ¹, D. Sathianarayanan ¹, R. Ramesh ¹, G. Harikrishnan ¹, T. Chowdhury ¹, V. B. N. Jyothi ¹, S. B. Pranesh ¹, V. Doss Prakash ¹, M. A. Atmanand ¹

Affiliations
1 National Institute of Ocean Technology, Ministry of Earth Sciences, Chennai 600 100, IN

Abstract

In India, scientific investigations of ocean basins have been in progress for more than five decades using indirect and direct measurement devices. These studies were aimed at resource identification, ecological, palaeo-oceanographic and palaeo-climatic research. To cater to the need of the ocean community, Remotely Operated Vehicles (ROV) rated for 6000 m (ROSUB 6000) and 500 m (PROVe-500) operational depths have been developed at the National Institute of Ocean Technology, MoES, Chennai. This article reports the design considerations for unmanned remotely operated underwater vehicles and the outcome of scientific expeditions conducted for deep sea mineral exploration, ocean biodiversity and polar science.

Keywords

Biodiversity, Ocean Resources, Remotely Operated Vehicle.

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G. A. Ramadass ¹, N. Vedachalam ¹, S. Ramesh ¹, D. Sathianarayanan ¹, A. N. Subramanian ¹, R. Ramesh ¹, T. Chowdhury ¹, S. B. Pranesh ¹, M. A. Atmanand ¹

Affiliations
1 National Institute of Ocean Technology, Ministry of Earth Sciences, Chennai 600 100, IN

Abstract

Human occupied vehicles (HOV) offer enhanced manoeuvering over the remotely operated vehicles and autonomous underwater vehicles. The presence of human increases the dexterity of the HOV operations, but at the same time, the man-rated vehicle design and operation requires significant attention to vehicle reliability, and in turn human safety. This article details the challenges involved in the design and development of deep water HOV, with specific reference to the 6000 m depth-rated HOV designed by the MoES– National Institute of Ocean Technology for enhancing India’s engineering capability in the deep ocean scientific research.

Keywords

Ballast, Batteries, Deep Ocean, Human Occupied Vehicle, Navigation.

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B. Vignesh Kumar ¹, J. V. Anisha Shafni ¹, V. Deepak Samuel ¹, K. R. Abhilash ¹, R. Purvaja ¹, R. Ramesh ¹

Affiliations
1 Conservation of Coastal and Marine Resources Division, National Centre for Sustainable Coastal Management, Ministry of Environment, Forest and Climate Change, Government of India, Anna University Campus, Chennai 600 025, IN

Abstract

The horned helmet Cassis cornuta (Linnaeus 1758) is the largest of all helmet shells belonging to the family Cassidae. In India, C. cornuta is protected under the Wildlife Protection Act, 1972 (Schedule- I, Part IV-B) due to its conservation importance. Also, it is one of the most sought after tropical marine molluscs in illegal trading. In the present study, we have performed DNA barcoding for this species using the mitochondrial marker gene, cytochrome c oxidase subunit 1 (COI), and deposited the data at GenBank (accession no. MK878541). The evolutionary history was inferred adopting the maximum likelihood method and Kimura 2-parameter model by encompassing representative organisms belonging to the genus Cassis. As C. cornuta is in great demand among shell collectors and is illegally traded across countries, the DNA barcode data available in the public database would provide an additional checkpoint in reducing the chance of unlawful trade of this shell. Further, it strengthens conservation management practices, particularly at the port of entries where portable DNA barcoding facilities are in practice.

Keywords

Cassis cornuta, COI Gene, DNA Barcoding, Protected Species.

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