Current Science

Supriyo Kumar Das ¹, Joyanto Routh ², Alakendra N. Roychoudhury ³

Affiliations
1 Department of Geology, Presidency University, 86/1 College Street, Kolkata 700 073, IN
2 Department of Water and Environmental Studies, Linköping University, 581 83 Linköping, SE
3 Department of Earth Sciences, Stellenbosch University, Private Bag X1, Maiteland 7602, ZA

Abstract

Studying the biogeochemistry of shallow lake sediments, especially the source of sedimentary organic matter (OM), is challenging because of the low preservation of OM in shallow lake sediments. Here we report the source of sedimentary OM in a shallow freshwater lake, Verlorenvlei, in South Africa using a number of biogeochemical proxies. Elemental carbon and nitrogen ratio (C/N), and stable C and N isotopes (δ ¹³C andδ ¹⁵N) indicate algal source of the sedimentary OM. Total organic and inorganic C, different phosphorus fractions, δ¹³C and δ¹⁵N values indicate repetitive presence of non-N-fixing cyanobacteria under moderate N-limited conditions. Cyanobacterial population in Verlorenvlei is likely influenced by the availability of dissolved inorganic C. Cyanobacterial proliferation in the lake has ceased with accelerated N input as recorded at the top of the core.

Keywords

Carbon, Cyanobacteria, Nitrogen, Organic Phosphorus, Shallow Lakes, Stable Isotopes.

Full Text

   

Supriyo Kumar Das ¹, Debasish Dutta ², Saranya Naskar ², Snigdha Palchaudhury ¹, Rabindranath Gayen ², Abhijit Dey ³

Affiliations
1 Department of Geology, Presidency University, College Street 86/1, Kolkata 700 073, IN
2 Department of Physics, Presidency University, College Street 86/1, Kolkata 700 073, IN
3 Department of Life Sciences, Presidency University, College Street 86/1, Kolkata 700 073, IN

Abstract

Jagadish Chandra Bose observed rhythmic electrical oscillations or pulsations in living cells of the innermost layer of cortex, and linked them to upward pumping of water into the xylem¹. Bose measured bioelectric potentials in Indian telegraph plant Desmodium (Bon Charal or forest churl) using the cresograph, a self-invented instrument, that consisted of an electric probe, a galvanometer, an electric dry cell and a thin copper wire. He connected the galvanometer to one point of a potted plant and the probe to another point of the plant, and slowly inserted the probe into the stem. The galvanometer showed momentary deflection for a longer period after the probe reached the innermost layer of the cortex. Bose observed a physiological motif and interlinked the measured pulsations in cellular electric potentials with oscillations in cell turgor pressure².

Full Text

   

Supriyo Kumar Das ¹, Santanu Ghosh ¹, Sven Isaksson ², Kerstin Liden ², Arunabha Dey ¹

Affiliations
1 Department of Geology, Presidency University, Kolkata 700 073, IN
2 Department of Archaeology and Classical Studies, Stockholm University, 106 91 Stockholm, SE

Abstract

Organic residue, often amorphous or invisible to the naked eye, cannot be characterized by using traditional archaeological techniques. Such residues are a result of plant and animal product processing either by heating or due to mechanical action^1-4. Organic residues, in contrast to the food crusts, are often better preserved in the mineral matrices of the pottery fabric that protect the organic molecules from microbiological degradation^4,5. The biomolecular components of organic residue are used as a tool to identify the source of the residue⁶, and to glean information on economic and subsistence practices associated with prehistoric cultural and technological traditions^4,7-9. This makes organic residue analysis a well-established tool in geoarchaeology.

Full Text