Some problems related to the measurements of primary production using radiocarbon technique

The SCOR/IBP Working Group-24 held its first meeting in Southampton (U.K.) from 30 July to 1 August 1968 under the chairmanship of Dr. T. R. PARSON(Canada). The members of this Working Group were : Dr. O. I. KOBLENTZ- MISHK(EU .S.S.R.), Prof. S. ICHIMURA(Japan), Dr. P. D. V. SAVAGE (U.K.) and Dr. S. Z. QASIM (India). The terms of reference of the Working Group were: "To review and suggest the best methods for estimating primary production under special conditions, such as those found beneath polar ice, and the turbid conditions found in estuaries, heavily polluted waters and exceptionally eutrophic or oligotrophic waters"

Effect of intensity and quality of illumination on the photosynthesis of some tropical marine phytoplankton

Using solar energy as a source of illumination, photosynthesis in 11 species of marine plankton algae was studied as a function of light intensity. From the photosynthesis-light curve for each organism, the saturation points (Is) in different organisms were determine

Genetic identification and phylogenetic relationships of Indian clariids based on mitochondrial COI sequences

Mitochondrial cytochrome C Oxidase I (COI) sequence variation among the clariid fishes of India (Clarias magur, C. dussumieri and C. gariepinus) and their relationship with other representative clariids was studied in this work. Three species were sampled and together with 23 COI sequences from GenBank were used to reconstruct phylogenetic relationships in the family Clariidae. The study revealed two clades: one consisting of the African species with C. dussumieri, and the other of Asian species suggesting the prevalence of intra-continental diversification of catfishes. This study further revealed that the genus Clarias is monophyletic. For the COI gene, the interspecies genetic divergence ranged from 0.056 to 0.182. The mean genetic difference between C. dussumieri and other selected African species in this study is 12.1%. It was also observed that the morphological similarity of C. dussumieri and C. magur was not replicated in the genetic level. Clarias dussumieri was more close to African catfish C. gariepinus thus indicating the utility of COI phylogeny to identify the well-known African-Asian relationships within catfishes. The results also showed that C. magur and C. batrachus are genetically distinct from each other

Association between age at disease onset of anti-neutrophil cytoplasmic antibody-associated vasculitis and clinical presentation and short-term outcomes

Objectives: ANCA-associated vasculitis (AAV) can affect all age groups. We aimed to show that differences in disease presentation and 6 month outcome between younger- A nd older-onset patients are still incompletely understood. Methods: We included patients enrolled in the Diagnostic and Classification Criteria for Primary Systemic Vasculitis (DCVAS) study between October 2010 and January 2017 with a diagnosis of AAV. We divided the population according to age at diagnosis: <65 years or ≥65 years. We adjusted associations for the type of AAV and the type of ANCA (anti-MPO, anti-PR3 or negative). Results: A total of 1338 patients with AAV were included: 66% had disease onset at <65 years of age [female 50%; mean age 48.4 years (s.d. 12.6)] and 34% had disease onset at ≥65 years [female 54%; mean age 73.6 years (s.d. 6)]. ANCA (MPO) positivity was more frequent in the older group (48% vs 27%; P = 0.001). Younger patients had higher rates of musculoskeletal, cutaneous and ENT manifestations compared with older patients. Systemic, neurologic,cardiovascular involvement and worsening renal function were more frequent in the older-onset group. Damage accrual, measured with the Vasculitis Damage Index (VDI), was significantly higher in older patients, 12% of whom had a 6 month VDI ≥5, compared with 7% of younger patients (P = 0.01). Older age was an independent risk factor for early death within 6 months from diagnosis [hazard ratio 2.06 (95% CI 1.07, 3.97); P = 0.03]. Conclusion: Within 6 months of diagnosis of AAV, patients >65 years of age display a different pattern of organ involvement and an increased risk of significant damage and mortality compared with younger patients

Seasonal fluctuations in the occurrence of Cladocera in the Mandovi-Zuari estuarine waters of Goa

138-142Annual fluctuations in environmental features were noticeable particularly in the concentration of salinity and nutrients. The cladocerans showed a wide range of salinity tolerance and exhibited positive correlation with chlorophyll a(r = 0.78). Evadne tergestina Claus and Penilia avirostris Dana were the 2 major species representing cladoceran population, the former being dominant (85.88%). Both the species were characterised by seasonality in distribution. Distribution patterns of each species in Indian coastal waters and their possible role as food source of pelagic fishes especially that of Indian mackerel are discussed

Primary Productivity &Carbon Assimilation Patterns in Tropical Marine Phytoplankton

205-211Primary productivity values measured at 3 stations in the Lakshadweep Sea (Laccadive Sea) varied from 0.44 to 2.11 mg Cm-3h-1 and were characterised by a distinct subsurface maxima. Over a diel cycle in the Minicoy Lagoon,the rates varied from 0.22 to 12.80 mg Cm-3h-1 and closely paralleled the diurnal changes in solar irradiance levels. Studies on the distribution of assimilated carbon into the major end products of photosynthesis showed that the synthesis of polysaccharides is favoured at higher light intensities. There was a steady decline in the levels of polysaccharides synthesized with a decrease in levels of light available for photosynthesis. The synthesis of lipid/LMWM (low molecular weight metabolites) was also favoured at higher light intensities. A highly significant relationship between the percentage of lipid/LMWM synthesized and the productivity rates per unit chl a suggests that the appearance of newly fixed carbon within this fraction is strongly dependent on the rates of photosynthesis at any given time. A higher proportion of protein synthesized was observed under conditions of low light intensity. Regression analysis between the percentage of protein synthesized and the productivity rates per unit chl a showed an inverse relationship. Changes in the nature of the end products of photosynthesis in relation to available light in 2 clones of marine phytoplankton, viz. Nitzschia closterium and Pleurosigma sp., were in general agreement with those observed in natural populations

Diel variation in phytoplankton pigments and primary production off Bombay

96-99Variations in biological parameters over 24 hr at 4 stations off Bombay indicated that chlorophyll a concentration, organic carbon production and particulate organic carbon (POC) were generally maximum during the day. Concentrations of pigments at any depth ranged from 0.09 to 1.74 (mg m-3). Similarly the production and POC varied from 1.15 to 86.12 (mgC m-3 d-1) and 107.6 to 585.4 (mgC m-3). 'Smaller phytoplankton' contributed 50 to 100% to the pigment of the total phytoplankton. The maximum in assimilation number was found when NH4-N and NO3-N were maximum

Phytoplankton assemblages and pigments in the exclusive economic zone of Mauritius (Indian Ocean)

163-168Nutrient enrichment studies showed that both inorganic salts of nitrogen and phosphorus were limiting for phytoplankton from the surface waters. This coupled with conditions of high insolation prevailing at this time (Sept.-Oct.), severely curtailed phytoplankton growth in the surface waters leading to formation of a distinct subsurface chlorophyll maximum (SCM). In the vicinity of Agalega islands, the enhancement of phytoplankton biomass was associated with an upwelling process caused by the confluence of the westward flowing branch of the South Equatorial Current with the Seychelles-Mauritius Ridge. The inadequacy of processes such as vertical diffusion and nutrient regeneration in sustaining phytoplankton in surface waters highlights the importance of current-driven upwelling in transporting nutrients to the surface waters of the euphotic column within this region

Distribution of Phytoplankton & Chlorophyll <i>a</i> around Little Andaman Island

248-252Surface chl a and phaeopigments of the whole phytoplankton varied from 0.02 to 0.085 mg/m3 (av. 0.043) and 0.017 to 0.068 mg/m3 (av. 0.039)respectively; chl a of the nannoplankton fluctuated from 0.013 to 0.085 mg/m3 (av.0.034) and phaeopigments from 0.014 to 0.064 (av.0.029). Depthwise distribution of phytoplankton chl a and phaeo-pigments showed an increasing trend up to 1% light in the 2 coral banks. Phytoplankton population ranged from 1400 to 4900 cells/litre. Dinoflagellates formed an important constituent unlike those of the Arabian Sea and coastal waters of Bay of Bengal. Comparison of environmental data from the shallow coral banks with those from similar locations in the Arabian Sea was made