Total visitors: 2,147  since 25-05-05

Indian Journal of Marine Sciences

 

 

 

ISSN: 0379-5136 

 

CODEN: IJMNBF

VOLUME  34

NUMBER 2

JUNE  2005

 

 

CONTENTS

 

Papers

 

Productivity measurements in the Bay of Bengal using the 15N tracer: Implications to the global carbon cycle

 

153-162

Sanjeev  Kumar & R.Ramesh

 

 

 

Inter-annual variability of phytoplankton blooms in the northern Arabian Sea during winter monsoon period (February-March) using  IRS-P4 OCM data

 

163-173

R.K.Sarangi, Prakash  Chauhan & Shailesh R. Nayak

 

 

 

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

 

174-187

Heiner  Fabian, Rolf  Koppelmann & Horst  Weikert

 

 

 

Mixed substrate degradation: Are consortia better than monocultures?

188-191

K.P. Krishnan & A.V.Saramma

 

 

 

Shear-induced splitting of a plume outflow in a stratified enclosed basin

192-211

A. A. Bidokhti

 

 

 

Statistical modelling of monthly mean sea level at coastal tide gauge stations along the Indian subcontinent 

 

212-224

K. Srinivas, V. Kesava Das & P.K. Dinesh Kumar

 

 

 

ENSO signature in the sea level along the coastline of the Indian subcontinent

225-236

K. Srinivas, P.K. Dinesh  Kumar & C. Revichandran

 

 

 

Short  Communication

 

Distribution of marine macro-algae at different salinity gradients in Chilika  lake, east  coast of India 

 

237-241

J .Rath & S. P. Adhikary

 

 

 

 

Indian Journal of Marine Sciences

Vol. 34(2), June 2005, pp. 153-162

 

Productivity measurements in the Bay of Bengal using the 15N tracer: Implications to the global carbon cycle

Sanjeev Kumar* & R.Ramesh

 

During September-October 2002 (Fall intermonsoon), a cruise was undertaken in the shelf and offshore Bay of Bengal onboard ORV Sagar Kanya as a part of the Bay of Bengal Process Study, when physical, chemical and biological parameters were measured in the Bay. This paper describes the first 15N based productivity measurements made in the Bay, which are comparable to the 14C based measurements made concurrently. Results show that the productivity to Chl a ratios have a mean of 2.6 3.3 / hr. Offshore stations have an average productivity of ~360 mgC /m2/d, whereas shelf stations have ~280 mgC /m2/d. The highest value of 875 mgC /m2/d was found at a station where the mixed layer depth was the maximum (~55m, approximately equal to the average photic depth during the cruise). Both offshore and shelf stations have an average f-ratio (ratio of new to total production, conservative estimate) of ~0.5. The f ratios in the Bay of Bengal, higher relative to its western counterpart, the highly productive Arabian Sea (f ~ 0.3), implies that the Bay is capable of removing the anthropogenic excess CO2 from the atmosphere at least as efficiently as the Arabian Sea, if not more, at least during the fall intermonsoon season. Nitrate from depth could be brought up during this season by frequent cyclonic activity. Present study provides the first direct confirmation of high new prodcution in the Bay, earlier suggested based on pCO2 measurements.

 

[Key words: New production, f-ratio, nitrate, carbon cycle, Bay of Bengal]

 

 

 

Indian Journal of Marine Sciences

 Vol. 34(2), June 2005, pp. 163-173

 

Inter-annual variability of phytoplankton blooms in the northern Arabian Sea during winter monsoon period (February-March) using IRS-P4 OCM data

*R.K.Sarangi, Prakash Chauhan & Shailesh R. Nayak

 

Phytoplankton bloom has been observed and interpreted utilizing Indian Remote Sensing Satellite (IRS-P4), Ocean Colour Monitor (OCM) sensor retrieved chlorophyll images for the northern Arabian Sea for three years period (2000-2002). The overall mean chlorophyll concentration was found higher in year 2001, when compared to years 2000 and 2002 in the selected bloom waters north of 15 N latitude. The algal blooms were most intense during the year 2001. The monthly sea surface temperature (SST) and its anomaly data retrieved from NOAA-NCEP archive have been correlated with the phytoplankton blooming conditions in the study area during February-March, 2000-2002. The SST maps of January and February show similar trend in the bloom (~26C) and non-bloom (~29C) water, but in March month the SST has been raised by about 3C in both the bloom and non-bloom waters for the three years. The SST anomaly has been observed to be of higher range (-3 to +4C) in February and March 2001 and the gradient is having significant link with the algal bloom period. The phytoplankton bloom and the hike in chlorophyll concentration during the winter monsoon season has been linked with winter cooling and the detrainment phenomenon and its relationship with SST and SST anomaly has been discussed.

 

[Key words: Phytoplankton bloom, northern Arabian Sea, winter monsoon, IRS-P4 OCM, NOAA-NCEP SST]

 

 

 

 Indian Journal of Marine Sciences

 Vol. 34(2), June 2005, pp. 174-fo187

 

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

Heiner Fabian*, Rolf Koppelmann & Horst Weikert

 

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 m 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.

 

[Key words: Zooplankton, copepoda, Indian Ocean, Arabian Sea]

 

 

 

Indian Journal of Marine Sciences

Vol. 34(2), June 2005, pp. 188-191

 

Mixed substrate degradation: Are consortia better than monocultures?

K.P. Krishnan* & A.V. Saramma

 

In the present study, an attempt has been made to understand the behaviour of bacterial cultures in consortia. The rate of degradation of proteins, carbohydrates and lipids by three strains of Bacillus were determined individually and in consortium. Comparison of the degradation rates in consortia with single substrate rates revealed that in consortia there is a synergistic effect on protein and carbohydrate degradation while on lipid the rate decreased with time. In general, the present study shows that bacteria in consortia have higher potential to degrade organic substances present in the environment. More insights on this could lead to formulation of novel bioremediation strategies.

 

[Key words: Consortia, degradation rate, bacterial culture, Bacillus]

[IPC Code: Int. Cl.7: C12N 1/20; C12Q 1/02; C12R 1:07]

 

 

 

Indian Journal of Marine Sciences

Vol. 34(2), June 2005, pp. 192-211

 

Shear-induced splitting of a plume outflow in a stratified enclosed basin

 A. A. Bidokhti

 

In this paper we review the outflow data for the Persian Gulf and report on laboratory experiments with outflows from turbulent plumes falling into a pre-established density stratification in a long box. The experiments show the formation of coarse vertical structure, a result of shear layers generated by quasi-stationary internal wave modes. Applying a theory of Wong et al. [J. Fluid Mech., 434(2001) 209-244] for shear layers generated by plume outflows at the bottom of a tank, we interpret the intrusion structure in terms of downward-propagating low frequency waves excited by the outflow. In the presence of an upward mean advection driven by entrainment into the plume and displacement by the outflow a mode becomes stationary in the tank and causes the outflow to split into multiple horizontal (T, S) intrusions with thickness given by the dominant vertical wavelength. Central to this thesis are single-component experiments, which show that double-diffusive convection is not responsible for the coarse structure. When the laboratory plume is given both temperature and salinity contrasts from the surroundings, double-diffusive convection is evident and tends to modify the smooth gradients into interfaces and convecting layers. However, the convection is parasitic on the vertical T, S gradient perturbations generated by the shearing modes. In comparing the laboratory results and theory with the data for the Persian Gulf outflows, we tentatively propose that this outflow, as it passes over the sloped boundary, induces internal waves whose normal mode structure may fold up the outflow and create the coarse layers. We also find that the double-diffusive effects are too small to influence the shearing modes in ocean outflows.

 

[Key words: Stratified intrusions, shear modes, internal waves, double-diffusive convection, outflows, marginal seas, Persian Gulf]

 

 

 

Indian Journal of Marine Sciences

 Vol. 34(2), June 2005, pp. 212-224

 

Statistical modelling of monthly mean sea level at coastal tide gauge stations along the Indian subcontinent

*K. Srinivas, V. Kesava Das & P.K. Dinesh Kumar

 

This study investigates the suitability of statistical models for their predictive potential for the monthly mean sea level at different stations along the west and east coasts of the Indian subcontinent. Statistical modelling of the monthly mean sea level at 15 selected tide gauge stations (8 stations on the west and 7 stations on the east coast) along the coastline of the Indian subcontinent was attempted using autoregressive, sinusoidal and exponentially weighted moving average (EWMA) techniques. Statistics pertaining to the mean seasonal cycle as well as interannual variability are also presented. A strong domination of the annual cycle over the semi-annual cycle was seen at ten stations. The maximum seasonal sea level ranges were observed along the west coast at Bhavnagar (63 cm) and along the east coast at Sagar Island (48 cm). While the autoregressive and sinusoidal models were satisfactory, EWMA technique was found to be the best of all. Tuticorin on the east coast, and Mormugao on the west coast have shown minimum RMSEs for the corresponding coasts for all the three models, while Bhavnagar on west coast has shown very high RMSE values. The EWMA technique (which yields forecast with a lead time of only one month) gave the lowest root mean square errors relative to the verifying observations.

 

[Key words: Statistical modelling, monthly mean sea level, seasonal and interannual variabililty, oceanography, meteorology, Indian subcontinent]

[IPC Code: Int.Cl.7 G06F169:00]

 

 

 

Indian Journal of Marine Sciences

 Vol. 34(2), June 2005, pp. 225-236

 

ENSO signature in the sea level along the coastline of the Indian subcontinent

K. Srinivas*, P.K. Dinesh Kumar & C. Revichandran

 

Evidence for the signature of El Nino-Southern Oscillation (ENSO) phenomenon in the monthly mean sea level at 8 tide gauge stations on the west coast and 7 stations on the east coast of the Indian subcontinent is presented. The Southern Oscillation Index (SOI, indicator of the ENSO phenomenon) available continuously from 1933 onwards, was utilized to examine the relationship between sea level and ENSO. The relationship between sea level and SOI is direct, with the sea level decreasing during El Nino years and increasing during La Nina years. The signature of ENSO is particularly conspicuous in the sea level records on the east coast as compared to those on the west coast. Reduced rainfall over the Indian subcontinent and resultant river discharges, remote forcing by interannual zonal winds along the equator and reduced Indonesian Throughflow could be the probable factors explaining the low sea level along the coastline of the Indian subcontinent during ENSO events. The interannual sea level along the coastline of the Indian subcontinent shows more or less synchronous movement-the rise and fall is nearly simultaneous. At low frequency, spatial coherence of sea level is very large.

 

[Key words: Sea level, El Nino-Southern Oscillation, Southern Oscillation Index, Indian coastline]

 

 

 

Indian Journal of Marine Sciences

 Vol. 34(2), June 2005, pp 237-241

 

Short Communication

 

Distribution of marine macro-algae at different salinity gradients in Chilika lake, east coast of India

J. Rath & S. P. Adhikary*

 

Biomass of macro-algal forms with their seasonal and sectoral distribution in the salinity gradient of Chilika lake was evaluated. Three macro-algae, Gracilaria verrucosa, Enteromorpha intestinalis and Chaetomorpha linum occured abundantly in the lake throughout the year. These organisms preferred moderate salinity of Southern and Central sectors and their biomass changed in response to the salinity levels during different seasons. Gracilaria verrucosa  and E. intestinalis did not grow in the Northern sector where the salinity level was least in the lake. Maximum biomass was obtained in the winter followed by summer and rainy seasons. The total biomass of 26,963 tonnes dry weight in 7.63% of the total area surveyed showed richness of macro-algal resources in the lake. Of this, occurrence of 14,467 tonnes of the economically important alga Gracilaria verrucosa suggests its possible exploitation for agar production.

 

[Key words: Chilika lake, macro-algae, Gracilaria verrucosa, Enteromorpha intestinalis Chaetomorpha linum,    biomass, salinity gradient]