Showing papers by "National Institute of Oceanography, India published in 1996"

Mechanism of the biological response to winter cooling in the northeastern Arabian Sea

Abstract: THE Arabian Sea is one of the most biologically productive ocean regions1, mainly due to the upwelling of nutrients during the summer (southwest) monsoon. But the northern Arabian Sea continues to sustain fairly high biological production after the upwelling season and during much of the winter (northeast) monsoon2–4. The processes that enable this high winter productivity have hitherto been poorly understood, being variously attributed to surface cooling effects2,3 or wind-driven changes in ocean circulation4. Here we present physical, chemical and biological data that indicate that sea surface cooling drives convection processes that lead to the injection of nutrients up into the surface waters of the northeastern Arabian Sea during winter, and that this mechanism of nutrient supply is a dominant control on winter productivity. Observed seasonal changes in bacterial and microzooplankton populations may provide an explanation for the Arabian Sea 'paradox'5–8 that mesozooplank-ton biomass remains more or less invariable throughout the year.

Degradation of lignin and decolorization of paper mill bleach plant effluent (BPE) by marine fungi

Abstract: Very little is known about BPE decolorization or lignin degradation by marine fungi. In this study, we report on the ability of three marine fungi to produce the lignin modifying enzymes; laccase, manganese peroxidase (MNP) and lignin peroxidase (LIP), and to mineralize 14C-ring-labeled synthetic lignin. We also demonstrate, for the first time, the ability of these marine fungi to decolorize paper mill BPE.

EFFECT OF LOW TEMPERATURE ON THE STEREOISOMER COMPOSITION OF β-CAROTENE IN THE HALOTOLERANT ALGA DUNALIELLA BARDAWIL (CHLOROPHYTA)1

Abstract: Dunaliella bardawil Ben-Amotz & Avron, a β-carotene-accumulating halotolerant alga, was analyzed for the effect of growth temperatures on its pigment content and on the stereoisomeric composition of β-carotene by the use of advanced liquid chromatography and photodiode array detection. Decreasing culture temperature from 30° to 10°C increased the β-carotene content twofold and the ratio of 9-cis to all-trans β-carotene fourfold, with no significant changes in the other cell pigments. The variation of total β-carotene content by temperature was correlated with the integral irradiance received by the algal culture during a cell division cycle, whereas the 9-cis stereoisomer increased over the amount expected by that integration. The massive accumulation of 9-cisβ-carotene within the β-carotene globules is interpreted as indicating that the oily 9-cis stereoisomer protects against the crystallization of all-trans β-carotene at low temperatures.

Atmospheric Input of Nutrients and Dust to the SE Mediterranean

Abstract: Concentrations of dissolved nutrients (PO4, NO3, NH4 and Si(OH)4) and pH have been monitored in 84 rain water samples collected during 3 winters at the northern Mediterranean Israeli coast (Haifa). The main dissolved inorganic nitrogen (DIN) compound was nitrate, with concentrations between 4.2 and 300 μM. Ammonium was dominant only in 12 out of 60 events, and its concentrations ranged between 2.2 and 96.9 μM. Phosphate showed a range of concentrations between 0.09 and 8.8 μM. High silicic acid concentrations (>2 μM) were detected only during relatively basic rains (pH>6), probably due to greater dissolution of quartz and clay particles into rain water under more basic conditions. Although about 30% of the rains are considered to be acid rains, their main H+ donor is non-seaspray sulfate and not nitrate. Nitrate and phosphate showed similar temporal variability, suggesting their common origin for most of the rain events.

Influence of food concentration, temperature and salinity on the larval development of Balanus amphitrite

Abstract: Influence of food concentration (0.5, 1 and 2 x 105 cell ml−1 ofSkeletonema costatum), temperature (20 and 30°C) and salinity (15, 25 and 35‰) on the larval development ofBalanus amphitrite (Cirripedia: Thoracica) was examined. The mortality rate at 20°C was lower than at 30°C in general. Increase in food concentration from 0.5 to 1 x 105 cells ml−1 improved the survival rate, but this was not evident when food concentration was increased to 2 x 105 cells ml−1. The results indicate that food availability and temperature jointly determine the energy allocation for metamorphic progress. It was observed that the influence of the tested variables varied with instar. At 20 °C the mean duration of the second instar exceeded 3 d and was much longer than other instar durations. The fourth, fifth and sixth instars and the total naupliar period showed that the effect of different salinities at given food concentrations was negligible at 20°C, while at 30°C there was a marked decrease in duration with increasing salinity.

Respiration rates in subsurface waters of the northern Indian Ocean: Evidence for low decomposition rates of organic matter within the water column in the Bay of Bengal

Abstract: Depth profiles of activity of the respiratory electron transport system (ETS) have been generated at several locations in the northern Indian Ocean. The results reveal much lower ETS activities in subsurface waters of the Bay of Bengal than those measured in the Arabian Sea. Lower respiration rates in the Bay of Bengal are corroborated by the much weaker north-south gradients in oxygen and total carbon dioxide. These are, however, in conflict with the higher sinking fluxes of organic carbon measured with sediment traps. The observations support the view that particulate organic matter may undergo a lesser degree of oxidation in the water column through its incorporation into rapidly sinking matter, perhaps as a result of the massive inputs of terrigenous matter in the Bay of Bengal. The differential respiration rates may cause changes in the distribution of suspended particulate matter and may also explain why the Bay of Bengal is not a site of water-column denitrification in spite of an apparently slower renewal of the intermediate waters as compared to the Arabian Sea.

HPLC analysis of phytoplankton pigments from Lake Kinneret with special reference to the bloom-forming dinoflagellate Peridinium gatunense (Dinophyceae) and chlorophyll degradatio products

Abstract: Photosynthetic pigments extracted from the paniculate material of the water column of Lake Kinneret were studied throughout the periods of May 1988-June 1989, and November 1993-November 1994, by means of HPLC. The temporal and vertical variation of the pigment suite found agreed with the microscopically determined phytoplankton record. The regression calculations of taxon-specifi c biomass with the corresponding signature pigments suggest that pigment analysis may be a useful tool for the monitoring of bloom-forming species, e.g. the dinoflagellate Peridinium gatunense Nygaard. The HPLC pigment analysis permitted the identification and quantification of chlorophyll degradation products, providing for the first time information about their composition in Lake Kinneret. Chlorophyllide a was the major detectable degradation product of chlorophyll o, varying between 1 and 9% of the chlorophyll a concentration. Other chlorophyll a derivatives appeared mostly in minor quantities. Pheophytin a was virtually lacking in all the samples. Removal rates of pigments, measured by sedimentation traps, indicated that the degradation of chlorophyll a via chlorophyllide a is a dynamic process that continues during the sedimentation of the phytoplankton particles.

The multixenobiotic resistance mechanism in the marine sponge Suberites domuncula : its potential applicability for the evaluation of environmental pollution by toxic compounds

Abstract: Experiments were carried out with the marine sponge Suberites domuncula to determine whether sponges may express-like mammalian tumor cells-a multidrug-like transporter system. The results demonstrate that sponge cells possess such a protective system termed multixenobiotic resistance (MXR) pump or P-glycoprotein-like pump. The protein was identified by antisera for the mammalian P170 multidrug resistance protein as a 130 kDa molecule. Binding studies were performed with 3H-vincristine (3H-VCR) and membrane vesicles; this process is ATP-dependent and inhibited by verapamil, which is known to reverse the multidrug-resistance phenotype in mammalian systems. Accumulation experiments were performed to demonstrate that the uptake of 3H-VCR is time-dependent, and increases at elevated extracellular levels of 3H-VCR. Application of the dyeing technique with calcein-AM, a suitable functional assay for multidrug transporter systems in mammal cells, also revealed the existence of the MXR pump in S. domuncula plasma membranes. These data demonstrate that S. domuncula is provided with a multidrug-like transporter, the MXR pump, which might function as a protection system for sponges in polluted environments.

Gracilaria conferta and its epiphytes: 3. Allelopathic inhibition of the red seaweed byUlva cf.lactuca

Abstract: In a previous study (Svirski et al., 1993), it was found that growth inhibition ofGracilaria spp., when cultured in the presence ofUlva cf.lactuca, was not due to shading or nutrient depletion, but seemed to be caused by competition for inorganic carbon or some type of allelopathy. In the present study, we attempted to differentiate between these two possible influences by (1) growing the two algae in biculture under various conditions, but keeping inorganic carbon levels constant and measuring net photosynthesis, respiration and growth rates, and by (2) measuring growth rates ofGracilaria spp. in the presence of extracts derived from media previously used to growUlva cf.lactuca.

Spreading of water masses and regeneration of silica and 226Ra in the Indian Ocean

Abstract: The magnitudes of silica and 226 Ra inputs to water (through particle regeneration, in situ , and from sediments) and the validity of observed Si and 226 Ra as tracers of water masses and advective processes were examined in the Indian Ocean using the GEOSECS data. The regenerated quantities of these two parameters were calculated as the difference between the observed and the expected concentrations; the latter were estimated from a three end-member mixing model employing potential temperature and salinity as conservative tracers. Here we present results on the quantitative spreading of the Antarctic Bottom Water (AABW); the Modified North Atlantic Deep Water (MNADW, also known as the Circumpolar Water) and the North Indian Deep Water (NIDW)-both these were represented together as High Salinity Deep Waters (HSDW); the Antarctic Intermediate Water (AAIW); the North Indian Intermediate Water (NIIW) and the Central Indian Water (CIW). Our results concur with recent results in the literature. Briefly, the northward flow of the AABW is uneven; the MNADW core layer is found to be closer to the Antarctic that spreads to the north, and AAIW is largely restricted to the Indian Ocean south of 10°S. Our results also reveal that: roughly 10% more AABW enters the Bay of Bengal than the Arabian Sea; there is greater possibility for deep waters to enter the Central Indian Basin from the Bay of Bengal; CIW occupies a larger part of the Bay of Bengal than of the Arabian Sea; and 10% of the NIIW reaches 30°S in the western Indian Ocean. The regenerations of Si and 226 Ra are mainly from the underlying sediments rather than through the dissolution of particles in the water column. The sediments in the northern parts seem to supply 226 Ra and Si to the rest of the Indian Ocean. At 10δS there is a subsurface (∼600 m) maximum in regenerated Si, which is possibly connected to the advection of particles by Indonesian waters. The maxima in regenerated 226 Ra and Si contribute about 50% and 30%, respectively, to the observed abundances, suggesting that the observed Si is a more useful tracer of water masses and mixing processes than 226 Ra. Linear relationships were found between regenerated Si and 226 Ra, but departures noticed for 226 Ra in the eastern Indian Ocean may be attributed to its release from particles transported by the Indian rivers. Diverse regimes with respect to the extent of sources and dissolution of opal were noted in the Indian Ocean: high diatom abundance but low Si regeneration in the Antarctic, high diatom abundance and high regenerated Si in the Arabian Sea, and low diatom abundance but high regenerated Si in the Bay of Bengal.

PCBs and organochlorine pesticides in krill, birds and water from Antartica

Abstract: The concentration levels of various congeners of PCHs and organochlorine pesticides were determined in krill, bird (emperor penguin) feathers and polynya water from different places around Dakshin Gangotri, Antarctica. t-HCH (α + γ isomers) was found to be present in considerable amounts in krill (141.3–164.3 pg g −1 ) but much less in penguin feathers (103.6–112.8 pg g −1 ) and polynya water (85.6–90.7 pg 1 −1 ). t-DDT (pp′-DDT+op′-DDT+pp′-DDE+op′-DDE) was detected in the range 31.1–44.4 pg g −1 in krill, 30.8–35.7 pg g −1 in the feathers and 24.8–26.5 pg 1 −1 in polynya water. A few congeners of PCBs were identified and quantified in all the samples, e.g. CB-101, CB-136, CB-151, CB-118, CB-153, CB-138. The concentration levels of PCBs in different samples are in the range 146.9–166.2 pg g −1 in krill, 105.8–113.6 pg g −1 in penguin feathers, and 96.8–103.8 pg 1 −1 in polynya water.

Variability of the oceanic boundary layer characteristics in the northern Bay of Bengal during MONTBLEX-90

Abstract: Variability of the ocean surface boundary layer characteristics on daily time-scale is studied utilizing the 3-hourly hydrographic data collected at a stationary location (20°N, 89°E) in the Bay of Bengal during August (18th–31st) and September (9th–19th), 1990 under MONTBLEX-90 field programme. The daily variations of temperature, salinity, σ0, mixed layer thickness, stability, heat content and rate of change of heat content in the upper 100 m are discussed in relation to prevailing weather (depressions) and hydrographic conditions (influx of fresh water, presence of eddies). The mixed layer thickness is examined through temperatureand σ0-based criteria considering also the surface salinity in the latter. TheT-based mixed layer thickness is always higher than that of σ0-based thickness. The rate of change of heat content is also computed up to the depth of 20°C and 14°C isotherms which takes into account the vertical motion and hence divergence. With the development of a low into a deep depression close to the study area, intense upwelling of subsurface cold waters is noticed from 100 m to the bottom of the surface mixed layer (20m) from 18th to 20th August. The upwelling is weakened by 21st August when the depression moved away from the study location. This variation of upwelling is supported by the variation of surface mixed layer thickness, static stability at 30 m depth, heat content in the upper 100 m and the heat content up to the depth of 20°C isotherm from 18th to 21st August. The rate of change of heat content in the upper 100 m and up to the depths of 20°C and 14°C isotherms leads to net heat storage during August and to net heat depletion during September. This together with the net surface heat gain lead to an import (197Wm−2) and export (233 Wm−2) of heat during August and September respectively through horizontal advective processes. These advective processes are attributed to the presence and movement of a warm core eddy through the study location.

Surficial clay mineral distribution on the southwestern continental margin of India: evidence of input from the Bay of Bengal

Abstract: Analyses of spatial distribution of clay minerals, sediment texture, and > 63 μm fractions of the grab samples from the S W continental margin of India exhibit: (i) higher contents of illite and chlorite on the lower slope and (ii) a well-defined no-clay zone on the entire shelf. Kaolinite and smectite are also present in significant quantities on the slope with traces of gibbsite and palygorskite in some samples. The high contents of illite and chlorite (clay minerals which are not abundant in the soils and estuarine sediments of this region) in the southern region of the study area are evidence for sediment contribution from the Bay of Bengal waters (BBW), which enter this region after the SW monsoon. Distribution trends of kaolinite, smectite, gibbsite, and laterite granules on the slope are suggestive of contribution from chemically weathered soils of Peninsular India.

Selective effect of the herbicide DCMU on unicellular algae — a potential tool to maintain monoalgal mass culture of Nannochloropsis

Abstract: The selective effect of DCMU on photosynthetic activity and growth rate was examined in several marine unicellular algae:Nannochloropsis sp. (Eustigmatohyceae),Dunaliella salina (Chlorophyceae)Isochrysis galbana (Prymnesiophyceae) andChaetoceros sp. (Bacillariophyceae). DCMU at 10−7 M caused an immediate decrease in the photosynthetic rate ofDunaliella andIsochrysis (about 50% inhibition), whereas 10−6 M imposed 80% inhibition in the photosynthetic rate ofChaetoceros. InNannochloropsis the rate was affected only when DCMU concentration exceeded 10−6M. Cellular growth rate of all studied algae was affected by DCMU in a similar manner to photosynthesis. The differential effect of DCMU was further examined in mixed cultures in whichNannochloropsis was cultivated together with an additional species simulating a contamination situation of aNannochloropsis culture. When DCMU was added at concentrations higher than 10−7 M, the growth of the competing algae significantly decreased, whileNannochloropsis maintained a relatively high growth rate. Consequently, after a growth period of 4 to 7 days a clear domination ofNannochloropsis was observed. These results demonstrate that DCMU and probably other herbicides of similar characteristics can be used effectively as a selective tool to suppress contaminating unicellular algae in open ponds in order to maintain a monoculture ofNannochloropsis.

Nucleotide sequence of the promoter region of Sparus aurata insulin-like growth factor I gene and expression of IGF-I in eggs and embryos.

Abstract: A genomic fragment of 3.1 kb, containing the promoter region of Sparus aurata insulin-like growth factor I (IGF-I) gene has been cloned and sequenced. This fragment contains exon 1 and exon 2 of Sparus aurata IGF-I gene. These two exons are identical in organization to the reported chum salmon IGF-I gene. Exon 1 contains 5' untranslated region and part of the signal peptide. Exon 2 codes for part of the signal peptide and part of the B domain. Nested polymerase chain reaction (PCR) revealed that a fragment was amplified from liver RNA when a common primer in the translated region and a primer located between 375 and 395 nucleotides upstream of the first methionine were used. No such amplification was obtained when the primer was located between 414 and 434 nucleotides upstream of the first methionine, suggesting that the first exon in Sparus IGF-I gene starts 400-410 nucleotides upstream of the first methionine. Expression of IGF-I mRNA was studied in Sparus aurata using reverse transcription (RT)-PCR. An amplified fragment was found in unfertilized eggs and in embryos 4, 8, and 12 hours after fertilization, when oligonucleotides specific for Sparus aurata IGF-I cDNA were used. A similar fragment was found when adult liver or one-day larval RNA were used. This fragment hybridized in a Southern blot to salmon IGF-I cDNA. These results demonstrate that the structure of IGF-I gene has been conserved in teleosts and IGF-I transcripts are present in fish during embryogenesis, probably of maternal origin.

A 27,000 year record of Red Sea Outflow: Implication for timing of post‐glacial monsoon intensification

Abstract: We reconstruct here the history of the Red Sea Outflow (RSO) over the past 27,000 years from an AMS 14C-dated high-resolution δ13C record of benthic foraminifera from the inner Gulf of Aden assuming the dominance of circulation over productivity in regulating benthic δ13C. The results reveal that, following a period of suppressed RSO due to shallow sill 24,000–18,000 yr BP, the Red Sea was vigorously flushed for ∼2,000 years before a major monsoon intensification caused the cessation of deep water formation from 15,500 to 7,300 yr BP. It appears that the monsoon intensification did lag behind insolation until 15,500 yr BP. Between 15,500 and the present, however, there was no lag in conflict with the previous reports, implying a negligible dampening effect of continental albedo during this period. However, since our analysis is confined to a single depth horizon and our record is sensitive to sea level, it has some limitations as an indicator of monsoon intensity.

Technical Note Multi-temporal change of Lake Brullus, Egypt, from 1983 to 1991

Abstract: Change detection algorithms have been applied to MSS data for monitoring changes inside and outside the Lake Brullus environment. Analysis of the results reveals occurrence of erosion and accretion along both sides of the lake inlet. During the study period (1983 to 1991), the lake area decreased by an average rate of 8·6 km2 per year mainly due to drying for land reclamation. Comparison between standardized and unstandardized principal components showed that the standardized PCs are more capable of identifying occurring changes. A simple technique, such as image differencing and ratioing, comprises a powerful method to emphasize changes, especially when we use thresholding.

Tropical sea surface temperatures and the earth's orbital eccentricity cycles

Abstract: The tropical oceanic warm pools are climatologically important regions because their sea surface temperatures (SSTs) are positively related to atmospheric greenhouse effect and the cumulonimbus-cirrus cloud anvil. Such a warm pool is also present in the central tropical Indian Ocean. Paleo-SSTs estimated by the radiolarian transfer functions for the last ∼200–1400 kiloyears (ka) in a deep-sea sediment core from this warm pool fluctuated within 2.75°C (26.14–28.89°C) around the threshold temperature (27 °C) for the super greenhouse effect. It is possible that this SST variation might have led to the corresponding fluctuation in the greenhouse effect and the cirrus cloud anvil in the geological past. These paleo-SSTs also exhibited cyclicities at ∼100- and ∼400-ka corresponding to the Earth's orbital eccentricity cycles. Results, therefore imply that the tropical Indian Ocean warm pool persisted during the Quaternary and the paleo-SSTs fluctuating at the orbital eccentricity frequencies might have modulated the intensity of greenhouse effect.

Bi-versus multichimerism in colonial urochordates: a hypothesis for links between natural tissue transplantation, allogenetics and evolutionary ecology.

Abstract: Allogenic colonies of the cosmopolitan ascidian Botryllus schlosseri may fuse upon contact through their blood vessels to form chimeric entities if they share at least one allele at a highly polymorphic haplotype, termed the fusibility-histocompatibility (Fu/HC) locus. Past studies have attributed several benefits to this chimerism, but none of the suggestions was confirmed by controlled laboratory studies. Furthermore, once Botryllus colonies fuse, a second allorecognition phenomenon begins which usually leads to the resorption of one partner in the chimera. Resorption is probably controlled by a multilevel hierarchial organization of the heterozygosity relatedness for several allorecognition elements (the Fu/HC and resorption loci), which also reflects the relative heterozygosity of each partner's genome. Consequently, the more heterozygotic partner will be the 'winner' in the resorption, leaving alive the most adapted genotype (sensu to the heterosis concept). However, recent studies have recorded that freely circulating stem cells from the 'subordinate' partner in the resorption phenomenon may parasitize the 'winner' for positions on the germ line. All the above studies have been performed on bichimeric entities. It is suggested here that formation of natural multichimeras in this species (resulting from an aggregated cosettlement of Fu/HC compatible colonies) produces more 'equilibrated' chimeric entities and alleviates the costs incurred through the contradicting heterosis and germ cell parasitism processes. This improves the interspecific competitive ability of the multifusion entities. Therefore, in this case, selection acts on the 'group' level, not the colony level, providing the evolutionary forces that shape the phenomenon of natural tissue transplantation in these organisms.

Chemical characterization of exopolysaccharides from the marine fouling diatom amphora coffeaeformis.

Abstract: Amphora coffeaeformis cells were grown in batch cultures under continuous illumination at 18°C for 10 d. Algal cells were removed by centrifugation, lyophilized and used for the extraction of exopolysaccharides using either 0.05 M EDTA, 1 M NaOH or 1.5 M NaCl. The 1.5 M NaCl treatment removed most exopolysaccharides. Glucose (81%) was the most abundant monosaccharide in the exopolysaccharides. The chemical composition data suggest that the exopolymers were acidic sulphated polysaccharides containing high concentrations of pyruvate (22%) and uronic acids (18%). These polysaccharides may play an important role in metal complexation and protection from desiccation in A. coffeaeformis.