A. Saravanakumar

Efficient synthesis of silver nanoparticles from Prosopis juliflora leaf extract and its antimicrobial activity using sewage

In this paper, aqueous extract of fresh leaves of Prosopis juliflora was used for the synthesis of silver (Ag) nanoparticles. UV-Vis spectroscopy studies were carried out to asses silver nanoparticles formation within 5 min, scanning electron microscopic was used to characterize shape of the Ag nanoparticles, X-ray diffraction analysis confirms the nanoparticles as crystalline silver and facecentered cubic type and Fourier transform infra-red assed that shows biomolecule compounds which are responsible for reduction and capping material of silver nanoparticles. The anti microbial activity of silver nanoparticle was performed using sewage. The approach of plant-mediated synthesis appears to be cost efficient, eco-friendly and easy methods.

Development of Nitrate Algorithm for the Southwest Bay of Bengal Water and Its Implication Using Remote Sensing Satellite Datasets

The in situ sampled and analyzed nitrate, chlorophyll and sea surface temperature (SST) during the period 2009-2010 from monthly coastal stations and cruise datasets have been interpreted for the southwest Bay of Bengal water to develop nitrate algorithm for remote sensing applications in ocean biogeochemical cycling. The monthly sampled data points were retrieved from the coastal water around Pondicherry, Cuddalore, Parangipettai and Nagapattinam along Tamil Nadu coast, India. The cruise data has been retrieved between the coastal and offshore water along the Chennai and Kakinada (AP) segment. The SST and chlorophyll datasets has been regressed with the nitrate three dimensionally with 105 in situ data points. Parabolic function has been fitted, producing significant relationship. During the following seasons: summer (April-June), pre-monsoon (July-September), monsoon (October-December) and post-monsoon (January-March) the coefficient of determination R2 value found to be 0.16, 0.34, 0.48 and 0.56 respectively. The satellite derived nitrate map has been generated for February 28, 2010 using Oceansat-2 OCM derived chlorophyll concentration and MODIS-Aqua derived SST basing on in situ modeled nitrate algorithm. The satellite derived nitrate concentration range has been observed to be 0.01 to 12.0 μg/L with high nitrate fronts off Tamil Nadu and Kerala coast around southern Indian tip. High nitrate and low chlorophyll (HNLC) condition has been of concern, where SST was high. Similar contrasting features in SST and nitrate images have been observed. The developed algorithm has been validated for a different dataset of March 16 and 18, 2010 and R2 value found to be 0.508 and the algorithm observed to be working satisfactory over the southwest Bay of Bengal region.

A massive infestation of sea snakes by cymothoid isopods.

In this study, a massive infestation of the sea snake Enhydrina schistosa by the cymothoid isopod Nerocila serra, commonly parasitizing fishes, is reported for the first time from India. This isopod was found attached on the different parts of the body of the snake. According to the month, the parasitic prevalence ranged from 30.8 to 55.3%, increasing during the monsson period. It was higher in female than in male snakes.

Inter-annual and seasonal variations in hydrological parameters and its implications on chlorophyll a distribution along the southwest coast of Bay of Bengal

Seasonal and inter-annual variability of hydrological parameters and its impact on chlorophyll distribution was studied from January 2009 to December 2011 at four coastal stations along the southwest Bay of Bengal. Statistical analysis (principal component analysis (PCA), two-way analysis of variance (ANOVA) and correlation analysis) showed the significant impact of hydrological parameters on chlorophyll distribution in the study area. The ranges of different parameters recorded were 23.8–33.8°C (SST), 4.00–36.00 (salinity), 7.0–9.2 (pH), 4.41–8.32 mg/L (dissolved oxygen), 0.04–2.45 μmol/L (nitrite), 0.33–16.10 μmol/L (nitrate), 0.02–2.51 μmol/L (ammonia), 0.04–3.32 μmol/L (inorganic phosphate), 10.09–85.28 μmol/L (reactive silicate) and 0.04–13.8 μg/L (chlorophyll). PCA analysis carried out for different seasons found variations in the relationship between physico-chemical parameters and chlorophyll in which nitrate and chlorophyll were positively loaded at PC1 (principal component 1) during spring inter-monsoon and at PC2 (principal component 2) during other seasons. Likewise correlation analysis also showed significant positive relationship between chlorophyll and nutrients especially with nitrate (r=0.734). Distribution of hydrobiological parameters between stations and distances was significantly varying as evidenced from the ANOVA results. The study found that the spatial and temporal distribution of chlorophyll was highly dependent on the availability of nutrients especially, nitrate in the southwest Bay of Bengal coastal waters.

Thermostable alkaline protease from newly isolated Vibrio sp.: extraction, purification and characterisation

An extracellular alkaline protease-producing Vibrio sp. was isolated from mangrove sediments of Vellar estuary. A 9.36-fold purification was achieved by a three-step purification procedure and the molecular weight of the enzyme was determined as 33 kDa by SDS-PAGE. The enzyme was active in a broad range of pH (6.0–11.0) and temperature (30–70°C), the optimum being at pH 9.0 and temperature 55°C. The enzyme was stable at alkaline pH range of 9–11 and up to a temperature of 60°C, after incubation for 1 h. Metals like Co2+, Hg2+, Ni2+ and Cu2+ inhibited the enzyme activity, whereas Fe2+, Ca2+ and Mn2+ were found to enhance the activity. The protease was found to be highly stable in the presence of oxidizing agents like H2O2, detergents such as SDS and Triton-X-100 and also some of the commonly used commercial detergents. The organic solvents like xylene, isopropanol, hexane and benzene were found to enhance as well as stabilize the enzyme activity. The extracellular production of the enzyme, the pH and thermal stability, and the stability in presence of oxidants, surfactants, commercial detergents and organic solvents, altogether suggest that it can be used as a laundry additive.

Trend in coral-algal phase shift in the Mandapam group of islands, Gulf of Mannar Marine Biosphere Reserve, India

The present study revealed proliferation of macro-algae modifying coral reef ecosystems in a different manner due to diseases and sedimentations in the Mandapam group of islands in the Gulf of Mannar. Benthic surveys were conducted with major attack of seven coral reefs diseases with high sedimentation rate, nine species of fleshy macro-algae (Turbinaria ornata, Turbinaria conaides, Caulerpa scalpelliformis, Caulerpa racemosa, Kappaphycus alvarezii, Padina gymnosphora, Sargassum wightii, Ulva reticulata and Calurpa lentillifera) proliferation against major corals life forms (Acropora branching, Acropora digitate, Acropora tabulate, coral massive, coral submassive, coral foliose and coral encrusting). The results confirm that diseased corals most favor to macro-algae growth (15.27%) rather than the sedimentation covered corals (8.24 %). In the degradation of coral life forms, massive corals were more highly damaged (7.05%) than any other forms. Within a short period of time (May to September), coral coverage shrank to 17.4% from 21.9%, macro-algae increased 23.51% and the average sedimentation rate attained 77.52 mg cm−2d−1 with persisting coral reef diseases of 17.59%. The Pearson correlation showed that the coral cover decreased with increasing macro-algae growth, which was statistically significant (r = −0.774, n = 100, P < 0.0005). The proliferation of the various macro-algae C. scalpellifrmis, T. ornata, C. racemosa, T. conaides, U. reticulata, S. wightii, K. alvarezii, P. gymnosphora and C. lentillifera increased with percentages of 6.0, 5.8, 5.7, 4.9, 4.2, 3.7, 2.7 and 1.9, respectively. If this trend continues, the next generation of new recruit corals will undoubtedly lead to a phase shift in Gulf of Mannar corals.

Length-weight relationship and relative condition factor of yellowfin tuna (Thunnus albacares) from Parangipettai coast, southeast coast of India

The length-weight relationship and the relative condition factor of yellowfin tuna Thunnus albacares collected on the Parangipettai coast, southeast coast of India was studied. Logarithmic equation...