Is δ15N of sedimentary organic matter a good proxy for paleodenitrification in coastal waters of the eastern Arabian Sea?

2009 ◽  
pp. 321-332 ◽  
Author(s):  
Rajesh Agnihotri ◽  
S. Wajih A. Naqvi ◽  
Siby Kurian ◽  
Mark A. Altabet ◽  
J. F. Bratton
Keyword(s):  
Organic Matter ◽  
Coastal Waters ◽  
Arabian Sea ◽  
Sedimentary Organic Matter ◽  
Eastern Arabian Sea ◽  
Good Proxy

Assessing temporal variation of coloured dissolved organic matter in the coastal waters of South Eastern Arabian Sea

2020 ◽  
Vol 39 (1) ◽  
pp. 102-109
Author(s):  
P. Minu ◽  
V. P. Souda ◽  
S. K. Baliarsingh ◽  
R. M. Dwivedi ◽  
Y. Ali ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Temporal Variation ◽  
Coastal Waters ◽  
Arabian Sea ◽  
South Eastern ◽  
Eastern Arabian Sea

Variations in δ13C values of sedimentary organic matter since late Miocene time in the Indus Fan (IODP Site 1457) of the eastern Arabian Sea

2019 ◽  
Vol 157 (6) ◽  
pp. 1012-1021 ◽  
Author(s):  
Boo-Keun Khim ◽  
Jongmin Lee ◽  
Sanbeom Ha ◽  
Jingu Park ◽  
Dhananjai K. Pandey ◽  
...  
Keyword(s):  
Organic Matter ◽  
Late Miocene ◽  
Arabian Sea ◽  
Sedimentary Organic Matter ◽  
Marine Phytoplankton ◽  
Land Plants ◽  
Terrestrial Organic Matter ◽  
Underlying Assumption ◽  
Catchment Areas ◽  
Eastern Arabian Sea

AbstractA 1108.6 m long core was recovered at Site U1457 located on the Indus Fan in the Laxmi Basin of the eastern Arabian Sea during IODP Expedition 355. Shipboard examinations defined five lithologic units (I to V) of the lower Paleocene to Holocene sedimentary sequence. In this study, δ13C values of sedimentary organic matter (SOM) confirm the differentiation of the lithologic units and further divide units III and IV into two subunits (1 and 2). Based on the underlying assumption that the SOM is decided primarily by a mixture of marine and terrestrial origins, δ13CSOM values at Site U1457 provide information on the terrestrial catchment conditions since late Miocene time. Low δ13CSOM values from late Miocene to late Pleistocene times are similar (c. −22.0 ‰) for the most part, reflecting a consistent contribution of terrestrial organic matter from the catchment areas characterized by dominant C3 land plants. Significantly lower δ13CSOM values (c. −24.0 ‰) in Unit III-2 (∼8 to ∼7 Ma) might be due to a greater input of C3 terrestrial organic matter. The increase in δ13CSOM values at ∼7 Ma and the appearance of high δ13CSOM values (c. −18.0 ‰) within Unit III-1 (∼7 to ∼2 Ma) indicate that C4 biomass overwhelmed the terrestrial catchment environment as a result of enhanced terrestrial aridity in the Himalayan foreland. The three-end-member simple mixing model, estimating the relative contributions of SOM from terrestrial C3 and C4 plants and marine phytoplankton, supports our interpretation of the distribution of C3 and C4 land plants in the terrestrial catchment environment.

Influence of environmental variables on the distribution and community structure of mesozooplankton in the coastal waters of the eastern Arabian Sea

2020 ◽  
Vol 39 ◽  
pp. 101480
Author(s):  
P. Ezhilarasan ◽  
Vishnu Vardhan Kanuri ◽  
P. Sathish Kumar ◽  
M. Kumaraswami ◽  
G. Durga Rao ◽  
...  
Keyword(s):  
Community Structure ◽  
Coastal Waters ◽  
Environmental Variables ◽  
Arabian Sea ◽  
Eastern Arabian Sea

scholarly journals Aerosol optical thickness and spatial variability along coastal and offshore waters of the eastern Arabian Sea

2011 ◽  
Vol 68 (4) ◽  
pp. 745-750 ◽  
Author(s):  
Harilal B. Menon ◽  
Nutan Sangekar ◽  
Aneesh Lotliker ◽  
Krishnaswamy Krishna Moorthy ◽  
Ponnumani Vethamony
Keyword(s):  
Spatial Variability ◽  
Optical Thickness ◽  
Coastal Waters ◽  
Arabian Sea ◽  
Aerosol Optical Thickness ◽  
Aerosol Size Distribution ◽  
Wave Radiation ◽  
Transfer Model ◽  
Eastern Arabian Sea

Abstract Menon, H. B., Sangekar, N., Lotliker, A., Krishna Moorthy, K., and Vethamony, P. 2011. Aerosol optical thickness and spatial variability along coastal and offshore waters of the eastern Arabian Sea. – ICES Journal of Marine Science, 68: 745–750. Data from the ocean-colour monitor (OCM) on board the Indian Remote Sensing Satellite P4 were used to analyse the spatial and temporal distribution of aerosol optical thickness (AOT) over the coastal and offshore waters of the eastern Arabian Sea. Zero water-leaving radiance from the near infrared (NIR) region was assumed for oceanic (open ocean) waters, because of the absorption of long-wave radiation by water molecules. As this assumption fails in coastal waters, it was necessary to correct for water-leaving radiance and sun glint to the NIR bands. The aerosol size-distribution parameter (α) was derived from a relationship between two NIR bands. The Ångström turbidity parameter (β) was obtained using an algorithm relating in situ hand-held, sun-photometer measurements and aerosol radiance (La) at 490 nm. The relationship between β and La (490) was derived with a sensitivity analysis, using a calibrated radiative transfer model. AOTs were retrieved for each pixel of 500 nm. The algorithm's performance was tested by comparing OCM-derived AOT values with in situ AOT and MODIS-derived values. Aerosol maps thus generated from January to December 2005 demonstrate the potential of this new retrieval method for producing AOT climatology from OCM data over coastal waters.

Monsoon variability during Mid Pliocene Warm Period: Evidence from oceanic denitrification at eastern Arabian Sea

2021 ◽  
Author(s):  
Padmasini Behera ◽  
Manish Tiwari
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Water Column ◽  
Arabian Sea ◽  
Water Productivity ◽  
Warm Period ◽  
Late Pliocene ◽  
High Productivity ◽  
Future Global Warming ◽  
Eastern Arabian Sea

<p>The variability of the South Asian Monsoon (SoAM) in warmer climatic conditions is not established yet. The Mid-Pliocene Warm Period (MPWP, 3.264 to 3.025 ma) is the most recent such event when the boundary conditions were similar to present with similar CO<sub>2</sub> concentration (more than 400 ppmv) and temperature (2-3°C higher than present). It presents the best analogue for understanding the impacts of future global warming on SoAM. The high-resolution study of denitrification from the eastern Arabian Sea can provide an insight into the SoAM variability during MPWP. Denitrification is the process by which nitrate is reduced to nitrogen gas (N<sub>2</sub> or N<sub>2</sub>O) during organic matter decay in oxygen minima zones in the water column. The denitrification process enriches the nitrate pool with <sup>15</sup>N, which is incorporated in the particulate organic matter. Denitrification is governed by the surface water productivity related to SoAM strength and the water column ventilation. We analyzed the nitrogen isotopic ratio of sedimentary organic matter (SOM, δ<sup>15</sup>N<sub>SOM</sub>) to examine the denitrification in the eastern Arabian Sea. Total nitrogen (TN %) and total organic carbon (TOC%) are used to estimate the surface water productivity from the sediment collected during expedition IODP 355, Hole U1456A. We find that the δ<sup>15</sup>N<sub>SOM</sub> values vary between 7-9 ‰ during 3.22-3.15 Ma and 2.9-2.75 Ma indicating high denitrification. High δ<sup>15</sup>N<sub>SOM</sub> values coincide with high productivity as shown by both TN and TOC. It shows two major periods in the late Pliocene (3.22-3.15 Ma and 2.92-2.75 Ma) associated with stronger denitrification and high productivity. These results indicate the intensification of SoAM during warmer periods of Late Pliocene and at the start of intensification of Northern hemisphere glaciation. The enhanced denitrification during this period could possibly be due to a reduction in deep water ventilation and monsoon driven upsurge in productivity.</p>

scholarly journals In Situ Profiling of Eastern Arabian Sea Coastal Waters Using a New Autonomous Vertical Profiler

2013 ◽  
Vol 38 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Elgar Desa ◽  
R. Madhan ◽  
Nitin Dabholkar ◽  
Shivanand Prabhudesai ◽  
Gajanan Navelkar ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Arabian Sea ◽  
Eastern Arabian Sea

Consistency of wave power at a location in the coastal waters of central eastern Arabian Sea

2019 ◽  
Vol 69 (5) ◽  
pp. 543-560 ◽  
Author(s):  
M. M. Amrutha ◽  
V. Sanil Kumar ◽  
Harsha Bhaskaran ◽  
Muhammed Naseef
Keyword(s):  
Coastal Waters ◽  
Arabian Sea ◽  
Wave Power ◽  
Eastern Arabian Sea ◽  
Central Eastern

scholarly journals The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes

2015 ◽  
Vol 12 (6) ◽  
pp. 1781-1797 ◽  
Author(s):  
R. M. Jeffreys ◽  
E. H. Fisher ◽  
A. J. Gooday ◽  
K. E. Larkin ◽  
D. S. M. Billett ◽  
...  
Keyword(s):  
Organic Matter ◽  
Water Depth ◽  
Metabolic Pathways ◽  
Arabian Sea ◽  
Food Source ◽  
Sedimentary Organic Matter ◽  
Food Sources ◽  
Δ13c Values ◽  
Wide Range ◽  
Chemosynthetic Bacteria

Abstract. The Arabian Sea is a region of elevated productivity with the highest globally recorded fluxes of particulate organic matter (POM) to the deep ocean, providing an abundant food source for fauna at the seafloor. However, benthic communities are also strongly influenced by an intense oxygen minimum zone (OMZ), which impinges on the continental slope from 100 to 1000 m water depth. We compared the trophic ecology of foraminifera on the Oman and Pakistan margins of the Arabian Sea (140–3185 m water depth). These two margins are contrasting both in terms of the abundance of sedimentary organic matter and the intensity of the OMZ. Organic carbon concentrations of surficial sediments were higher on the Oman margin (3.32 ± 1.4%) compared to the Pakistan margin (2.45 ± 1.1%) and sedimentary organic matter (SOM) quality estimated from the Hydrogen Index was also higher on the Oman margin (300–400 mg HC mg TOC−1) compared to the Pakistan margin (< 250 mg HC mg TOC−1). The δ13C and δ15N values of sediments were similar on both margins (−20 and 8‰, respectively). Stable isotope analysis (SIA) showed that foraminiferal cells had a wide range of δ13C values (−25.5 to −11.5‰), implying that they utilise multiple food sources; indeed δ13C values varied between depths, foraminiferal types and between the two margins. Foraminifera had broad ranges in δ15N values (−7.8 to 27.3‰). The enriched values suggest that some species may store nitrate to utilise in respiration; this was most notable on the Pakistan margin. Depleted foraminiferal δ15N values, particularly at the Oman margin, may reflect feeding on chemosynthetic bacteria. We suggest that differences in productivity regimes may be responsible for the differences observed in foraminiferal isotopic composition. In addition, at the time of sampling, whole jellyfish carcasses (Crambionella orsini) and a carpet of jelly detritus were observed across the Oman margin transect. Associated chemosynthetic bacteria may have provided an organic-rich food source for foraminifera at these sites. Our data suggest that foraminifera in OMZ settings can utilise a variety of food sources and metabolic pathways to meet their energetic demands.

scholarly journals Feeding habits of milk shark, Rhizoprionodon acutus (Ruppell, 1837) in the Gujarat coastal waters of north-eastern Arabian Sea

2018 ◽  
Vol 17 ◽  
pp. 78-86 ◽  
Author(s):  
Swatipriyanka Sen ◽  
S.K. Chakraborty ◽  
E. Vivekanandan ◽  
P.U. Zacharia ◽  
A.K. Jaiswar ◽  
...  
Keyword(s):  
Coastal Waters ◽  
Arabian Sea ◽  
Feeding Habits ◽  
North Eastern ◽  
Eastern Arabian Sea
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