Study on fluorescence emission and synchronous-scan fluorescence spectrea of Nitzschia hantzschiana solution with FE(III)

The characterization of the algal Nitzschia hantzschiana solution with (or without) Fe(III) was carried out using fluorescence emission and synchronous-scan spectroscopy. An emission peak (excited at 440 nm) was observed at 675 nm for Nitzschia hantzschiana solution. The effective characterization method used was synchronous-scan fluorescence spectroscopy (SFS). A wavelength difference (Delta lambda) of 90 nm was maintained between excitation and emission wavelengths. The peak was observed at about 236(ex) nm (326(em) nm) for synchronous fluorescence spectroscopy. Fe(III) was an effective quencher. The relationship between I-0/I (quenching efficiency) and c (concentration of Fe (III) added) was a linear correlation for the algal solution with Fe(III). Effects of pH on synchronous-scan fluorescence intensity were evident.

Pollen and diatom analysis on varved sediments in Lake Jues (Harz Mountains, Germany)

Studies combining sedimentological and biological evidence to reconstruct Holocene climate beyond the major changes, and especially seasonality, are rare in Europe, and are nearly completely absent in Germany. The present study tries to reconstruct changes of seasonality from evidence of annual algal successions within the framework of well-established pollen zonation and 14C-AMS dates from terrestrial plants. Laminated Holocene sediments in Lake Jues (10°20.70' E, 51°39.30' N, 241 m a.s.l.), located at the SW margin of the Harz Mountains, central Germany, were studied for sediment characteristics, pollen, diatoms and coccal green algae. An age model is based on 21 calibrated AMS radiocarbon dates from terrestrial plants. The sedimentary record covers the entire Holocene period. Trophic status and circulation/stagnation patterns of the lake were inferred from algal assemblages, the subannual structure of varves and the physico-chemical properties of the sediment. During the Holocene, mixing conditions alternated between di-, oligo- and meromictic depending on length and variability of spring and fall periods, and the stability of winter and summer weather. The trophic state was controlled by nutrient input, circulation patterns and the temperature-dependent rates of organic production and mineralization. Climate shifts, mainly in phase with those recorded from other European regions, are inferred from changing limnological conditions and terrestrial vegetation. Significant changes occurred at 11,600 cal. yr. BP (Preboreal warming), between 10,600 and 10,100 cal. yr. BP (Boreal cooling), and between 8,400 and 4,550 cal. yr. BP (warm and dry interval of the Atlantic). Since 4,550 cal. yr. BP the climate became gradually cooler, wetter and more oceanic. This trend was interrupted by warmer and dryer phases between 3,440 and 2,850 cal. yr. BP and, likely, between 2,500 and 2,250 cal. yr. BP.

Two new species of Nitzschia (Bacillariophyta) from shallow wetlands of Peninsular India

The majority of species belonging to the genus Nitzschia are distinguished by minute taxonomic features that are difficult to observe and document. Currently, geographical distributions for many species are recognized as cosmopolitan; in contrast endemic species are poorly documented and studied. Our study describes two new species of Nitzschia from shallow wetlands across the Bangalore urban district of peninsular India, Nitzschia taylorii, sp. nov. and Nitzschia williamsi, sp. nov. Morphological analyses of these new species were performed with light and scanning electron microscopy, and the ecology of inhabited wetlands are discussed briefly. New species records from urban polluted wetlands provide evidence for broadening taxonomic and ecological investigations of cosmopolitan genera like Nitzschia in the Southern Hemisphere.

Seasonal dynamics in the occurrence and abundance of Pseudo-nitzschia species in the Maheshkhali channel of the Bay of Bengal, Bangladesh

Occurrence and abundance of Pseudo-nitzschia spp. at the mouth of the Maheshkhali channel of the Bay of Bengal, Bangladesh were studied. Plankton and water samples were collected monthly from the sub-surface water during high tide at daytime from June 2000 to May 2001. Four species of Pseudo-nitzschia, namely P. pungens, P. pseudodelicatissima, P. delicatissima and P. australis were identified and among them the first three were most commonly encountered and they varied seasonally. Pseudo-nitzschia delicatissima was the dominant species during the autumn and winter months, whereas P. pungens was dominant during the summer and spring months. Pseudo-nitzschia pseudodelicatissima exhibited its highest abundance level during the summer. Surface water temperature, salinity, nitrate-nitrogen (N03-N) and phosphate-phosphorus (P04-P) were recorded and their relationship with the occurrence and abundance of Pseudo-nitzschia species were studied. At the mouth of the Maheshkhali channel, Pseudo-nitzschia cell density was highest in late autumn (November) when highest salinity (35 o/oo) and P04-P (3.2 mg/l) concentrations and low temperature (23 °C) were recorded.