Coccolithophores from the central Arabian Sea: Sediment trap results
Lina P Mergulhao 1, ∗,Rahul Mohan 2 ,V S N Murty 1 ,M VS Guptha 1,3 and D K Sinha 4
1 National Institute of Oceanography,Dona Paula,Goa 403 004,India.
2 National Centre for Antarctic and Ocean Research,Headland Sada,Vasco-da-Gama,Goa 403 804,India.
3 Present address:62,Sagar Society,Dona Paula,Goa 403 004,India.
4 Department of Geology,Banaras Hindu University,Varanasi 221 005,India.
∗e-mail:mlina@redi ffmail.com

Abstract: Sediment trap samples collected from a depth of 1018 m in the Central Arabian Sea Trap (CAST) at 14 ◦28 .N,64 ◦35 .E were analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994.Out of the twenty species of coccolithophores encountered,Gephyrocapsa oceanica,Emiliania huxleyi,Umbilicosphaera sibogae and Umbellosphaera irregularis were the most abundant.The total coccolithophore fluxes ranged from 28 . ×10 6 m −2 d −1
to 50 . ×10 6 m −2 d −1 showing seasonality with higher fluxes during the northeast (NE)monsoon and lower fluxes dur-
ing the spring intermonsoon.The higher fluxes were attributed to the enhancement of primary production in the central Arabian Sea due to southward extent of nutrients from the northeast Arabian Sea by the prevailing surface currents.Similarly,the occurrences of relatively lower coc-colithophore fluxes during the spring intermonsoon and southwest (SW)monsoon were attributed to the low nutrients in the warm,shallow surface mixed layer and downwelling to the south of Findlater Jet respectively in the central Arabian Sea.Some of the coccolithophore species such as E.huxleyi,G.oceanica,Calcidiscus leptoporus and Umbellosphaera tenuis showed signs of dissolution.


Structure of Charnockitic basement in a part of the Krishna–Godavari basin, Andhra Pradesh
I V Radhakrishna Murthy摯瑬敳獩 and S Bangaru Babu
Department of Geophysics, Andhra University, Visakhapatnam 530 003, India.
∗e-mail: ivr −murthy@yahoo.com

Abstract: A regional magnetic survey was carried out over an area of 8000 km 2 in Godavari districts of Andhra Pradesh,India,which is covered by the rocks of Eastern Ghat Mobile Belt (EGMB) viz., the Khondalitic series and Charnockites in the northern half and Permian to Mesozoic and Cenozoic sediments in the southern half,and forms a part of the Krishna –Godavari (K –G)basin. The survey brought out a strong NE –SW trending anomaly in the area covered by the rocks of Eastern Ghat Mobile Belt (EGMB),and a mild ENE –WSW trending anomaly in the area covered by the sediments of the Krishna –Godavari (K –G)basin.The NE –SW trending anomaly in the northern half could be attributed to the exposed/near surface Charnockite basement that has come closer to the surface as a result of Eastern Ghat Mobile Belt  (EGMB)tectonics.Explanation of  the mild ENE –WSW trending anomaly over the sediments of the Krishna –Godavari (K –G)basin required a faulted magnetic basement at depth downthrown towards the south.It is therefore concluded that the Charnockitic basement together with the Khondalite group of rocks which are folded and faulted during the di fferent phases of tectonics of Eastern Ghat Mobile Belt (EGMB) extend into the Krishna –Godavari (K –G)basin and further,were involved in faulting during the phases of formation and sedimentation in the Krishna –Godavari (K –G)basin.


Dynamics of transparent exopolymeric particles (TEP) and particle-associated carbohydrates in the Dona Paula bay, west coast of India
P V Bhaskar 1,2, ∗and Narayan B Bhosle 1
1 Marine Corrosion and Materials Research Division, National Institute of Oceanography,
Dona Paula, Goa 403 004, India.
2 Present address: Chemical Oceanography Division, National Institute of Oceanography,
Dona Paula, Goa 403 004, India.
∗e-mail: pbhaskar23@yahoo.com

Abstract: Surface seawater samples were collected over a period of 27 months at a shallow water station in Dona Paula bay from 1998 –2000.The samples were analyzed to assess the seasonal variations, inter-annual variability and the contributions of:
•transparent exopolymeric particles (TEP)concentration, •two forms of particle-associated carbohydrates –1.5 M NaCl/saline extracted (Sal-PCHO) and 10 mM EDTA-extracted (CPCHO)and •total bacterial abundance (TBA)to particulate organic carbon pool. A distinct inter-annual variability was observed with an increase in the bacterial abundance,chloro-phyll a (Chl a ,TEP and Sal-PCHO and their greater contribution to particulate organic carbon during May 1998 –1999 than in June 1999 –July 2000.Overall,there was no statistically signi ficant correlation of TEP with phytoplankton biomass (Chl a ,Sal-PCHO,CPCHO and hydrodynamic conditions.A weak inverse correlation was observed between TEP and TBA (r = −0 .p <. but the role of TEP as a C-source for bacteria was not evident.Both Sal-PCHO and CPCHO appeared to be two distinct forms of carbohydrates.Unlike CPCHO,Sal-PCHO concentrations showed a positive trend with Chl a and signi ficant linear correlation with bacterial abundance (r =0 .,p<0 .,n 48),indicating that Sal-PCHO as carbon source might have supported
bacterioplankton abundance.The mean %TEP-C contribution to the annual average organic carbon for 1998 –2000 was 6 . ±5 .,next only to phytoplankton-C (33 . ±22 .)and greater than bacterial-C (4 . ±4 .)or carbohydrate-C (< 3 .).Despite its greater contribution to the organic carbon pool,the contribution of TEP-C to the benthic carbon demand and its fate in the study area could not be ascertained in this study.


Geomorphic expression of late Quaternary sea level changes along the southern Saurashtra coast, western India
Nilesh Bhatt摯瑬敳獩 and Uday Bhonde
Department of Geology, Faculty of Science, M. S. University of Baroda, Vadodara 390 002, India.
∗e-mail: nilesh −geol@yahoo.com

Abstract: Geomorphic expression of land –sea interaction is preserved in the form of abandoned cli ffs, marine terraces,shore platforms and marine notches along the southern Saurashtra coast. These features have been used to ascertain the magnitude of sea level changes during late Quaternary.Notch morphology and associated biological encrustation have been used to estimate the magnitude and duration of palaeo-sea strands.Marine notches and other erosive features occurring between 12 and 15 m above the present Biological Mean Sea Level (BMSL) are attributed to the last interglacial corresponding to the Marine Isotopic Stage 5 (MIS-5). However,6 to 9 m upliftment of the coastal fringe is attributed to this sea level.The second major high sea strand was identi fied during the mid-Holocene when the sea rose 2 m above the present level.Notches corresponding to this high sea level are recorded 4 to 5 m above the present BMSL.


The influence of Indian Ocean Dipole (IOD) on biogeochemistry of carbon in the Arabian Sea
during 1997–1998
V VSSSarma
SORST, Japan Science and Technology Agency, Kawaguchi, Japan and Hydrospheric Atmospheric
Research Center, Nagoya University, Nagoya 464 8601, Japan.
e-mail: sarma@hyarc.nagoya-u.ac.jp

Abstract: Data on ocean color chlorophyll a (Chl a )obtained using Sea-viewing Wide Field of view Sensor (SeaWiFS),sea surface temperature (SST)by Advanced Very High Resolution Radiometer (AVHRR),and sea surface height (SSH)by TOPEX/POSEIDON were analyzed to examine the in fluence of Indian Ocean Dipole (IOD)on the physical and biogeochemical processes with special reference to phytoplankton primary production and air –sea fluxes of carbon dioxide in the Arabian Sea.Positive SST anomalies (SSTA)were found in the Arabian Sea (0.4 to 1 .8 ◦C)with higher values in the southwestern Arabian Sea that decreased towards north.The SSH anomalies (SSHA)and turbulent kinetic energy anomalies (TKEA)suggest decreased mixing during the IOD compared to the normal period.Chlorophyll a displayed signi ficant negative correlations with SSTA and SSHA in the Arabian Sea.Consistently,Chl a showed negative anomalies (low Chl a )during the IOD period which could be due to reduced inputs of nutrients.The photic zone integrated primary production decreased by 30%during the IOD period compared to the normal whereas pCO 2 levels were higher (by 10 –20 µatm).However,sea to air fluxes were lower by 10%during the IOD period due to prevailing weaker winds.Primary production seems to be the key process controlling the surface pCO 2 levels in the Arabian Sea.In future,the in fluence of IOD on ecosystem structure,export production and bacterial respiration rates are to be probed through in situ time-series observations.


Spatial and temporal distribution of methane in an extensive shallow estuary, south India
A Shalini 1 ,R Ramesh 1, ∗,R Purvaja 1 and J Barnes 2
1 Institute for Ocean Management, Anna University, Chennai 600 025, India.
2 School of Marine Sciences and Technology, University of Newcastle-upon-Tyne,
Newcastle-upon-Tyne, NE1 7RU United Kingdom.
∗e-mail: rramesh −au@yahoo.com

Abstract: Sedimentary methane (CH 4 fluxes and oxidation rates were determined over the wet and dry seasons (four measurement campaigns)in Pulicat lake,an extensive shallow estuary in south India. Dissolved CH 4 concentrations were measured at 52 locations in December 2000.The annual mean net CH 4 flux from Pulicat lake sediments was 3 . ×10 9 gyr −1 based on static chamber measurements.A further 1 . ×10 9 gyr −1 was estimated to be oxidized at the sediment –water interface. The mean dissolved concentration of CH 4 was 242 nmol l −1 (ranging between 94 and 501 nmol l −1 ) and the spatial distribution could be explained by tidal dynamics and freshwater input.Sea –air exchange estimates using models,account only for ∼13%(0 . ×10 9 gyr −1 )of the total CH 4 produced in sediments,whereas ebullition appeared to be the major route for loss to the atmosphere ( ∼63%of the net sediment flux).We estimated the total atmospheric source of CH 4 from Pulicat laketobe0.5to4 . ×10 9 gyr −1 .


Monsoon control on trace metal fluxes in the deep Arabian Sea
T M Balakrishnan Nair
Indian National Centre for Ocean Information Services (INCOIS), Ministry of Ocean Development,
‘Ocean Valley’, IDA–Jeedimetla (P.O), Hyderabad 500 055, India.
e-mail: bala@incois.gov.in

Abstract: Particulate fluxes of aluminium,iron,magnesium and titanium were measured using six time- series sediment traps deployed in the eastern,central and western Arabian Sea.Annual Al fluxes at shallow and deep trap depths were 0.47 and 0 .46 g m −2 in the western Arabian Sea,and 0.33 and 0 .47 g m −2 in the eastern Arabian Sea.There is a di fference of about 0 .9 –1 .8gm −2 y −1 in the lithogenic fluxes determined analytically (residue remaining after leaching out all biogenic particles) and estimated from the Al fluxes in the western Arabian Sea.This arises due to higher fluxes of Mg (as dolomite)in the western Arabian Sea (6 –11 times higher than the eastern Arabian Sea). The estimated dolomite fluxes at the western Arabian Sea site range from 0.9 to 1 .35 g m −2 y −1 . Fe fluxes in the Arabian Sea were less than that of the reported atmospheric fluxes without any evidence for the presence of labile fraction/excess of Fe in the settling particles.More than 75% of Al,Fe,Ti and Mg fluxes occurred during the southwest (SW)monsoon in the western Arabian Sea.In the eastern Arabian Sea,peak Al,Fe,Mg and Ti fluxes were recorded during both the northeast (NE)and SW monsoons.During the SW monsoon,there exists a time lag of around one month between the increases in lithogenic and dolomite fluxes.Total lithogenic fluxes increase when the southern branch of dust bearing northwesterlies is dragged by the SW monsoon winds to the trap locations.However,the dolomite fluxes increase only when the northern branch of the northwesterlies (which carries a huge amount of dolomite accounting 60%of the total dust load) is dragged,from further north,by SW monsoon winds.The potential for the use of Mg/Fe ratio as a paleo-monsoonal proxy is examined.


Observations of trace gases and aerosols over the Indian Ocean during the monsoon transition period
T K Mandal 1 ,Ateef Khan 1 ,Y Nazeer Ahammed 1 ,R S Tanwar 1 ,R S Parmar 1 ,
K S Zalpuri 1 ,Prabhat K Gupta 1 ,S LJain 1 ,Risal Singh 1 ,A PMitra 1 ,S CGarg 1 ,
A Suryanarayana 2 ,V SNMurty 2 ,M Dileep Kumar 2 and Andrew J Shepherd 3
1 National Physical Laboratory, New Delhi 110 012, India.
2 National Institute of Oceanography, Dona Paula, Goa 403 004, India.
3 National Ocean and Atmospheric Administration/Pacific Marine Environmental Laboratory, USA.

Abstract: Characteristics of trace gases (O 3 CO,CO 2 CH 4 and N 2 and aerosols (particle size of 2.5 micron) were studied over the Arabian Sea,equatorial Indian Ocean and southwest part of the Bay of Bengal during the monsoon transition period (October –November,2004).Flow of pollutants is expected from south and southeast Asia during the monsoonal transition period due to the patterns of wind flow which are di fferent from the monsoon period.This is the first detailed report on aerosols
and trace gases during the sampled period as the earlier Bay of Bengal Experiment (BOBMEX), Arabian Sea Monsoon Experiment (ARMEX)and Indian Ocean Experiments (INDOEX)were during monsoon seasons.The signi ficant observations during the transition period include:(i)low ozone concentration of the order of 5 ppbv around the equator,(ii)high concentrations of CO 2 CH and N and (iii)variations in PM2.5 of 5 –20 µ m 3.