8/6/2019 Essay,Abhinav Kumar

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In order to predict the Earth’s future climate, an increasedunderstanding of climate variability during the Holoceneperiod (11,500 B.P. to present) is critical. Seasonal

reversals in the southwest and northeast Indian OceanMonsoon (IOM) strongly influence weather and climaticconditions between 30°N and 30°S over the African,Indian, and Asian landmasses. Even small-scale variability

in rainfall across the Indian sub-continent, where thesouthwest monsoon accounts for 80% of the precipitation,has great impacts on socio-economic conditions. Thus, asrecently as the late 1960s, El Niño related IOM failure for

three consecutive years resulted in 1.5 million deaths inIndia from famine.

Scientists have recognized the unique value of speleothems as one of the most detailed natural archives on

Earth. Stalagmites are generally, undisturbed by humanactivities, and they record climate-dependent parameters ondecadal-centennial-millennial scales. Our specific objectivein this study is to reconstruct a high-resolution late glacial

to near-modern paleoclimate record based on differentphysical and geochemical proxies over time intervals whenrapid climatic transitions have occurred. In addition, we

also want to establish the role of biological processesinvolved in formation of speleothems. To deducepaleoclimatic information from carbonate deposits, which

is precipitated under non-equilibrium-conditions, it isimportant to improve the understanding of biological

processes involved in calcite precipitation.In this project, we conducted laboratory

experiments with calcium carbonate precipitating bacteriaisolated from the stalagmite deposits collected from Krem

Syndai in Meghalaya, India. The medium used to culturethese bacteria was designed in accordance to the drip watercomposition. These experiments helped us to: 1) establishthe fact that microbes are involved in formation of stalagmites, and 2) investigate, and quantify the potential

effects of biological processes in isotopic fractionation.

Figure.1 shows the change in optical density as afunction of bacterial growth and biocalcification.Theresults suggests a positive correlation (r =0.925) between

pH and microbial growth, which coincides with enhancedcalcite precipitation. In previous studies various species of Bacillus were involved in bio-calcification. We haveisolated a new strain S4 that has been partially identified by

16S rDNA sequencing. The strain shows less than 95%similarity with any of the existing microbial stains. XRDwas used to identify the minerals precipitated by themicrobe. The presence of crystalline calcite in the growth

medium (Fig. 2) indicates that the bacteria possibly servedas nucleation sites during mineralization. The precipitatewas also studied for isotopic fractionation of δ13C and δ18O.

Participation in the Goldschmidt conference willallow me to present my work to an international forum and

ensure fruitful and lively discussions on a theme, which islikely to generate lot of interests with geoscientists andpaleoclimatologists. Rarely such large international

geological congresses are held in India, which providesyoung researchers an exposure to cutting-edge andinnovative research themes in geosciences. Apart from theenhanced practical skill and international professional

experience bestowed by the Goldschmidt forum, interactionwith the diverse research community in geosciences will

augment keener insights, innovative thinking, andincorporate new ideas for my research. The interaction willprovide a critical insight into my work, which will be a

milestone at the start of my research endeavor. Further, thisexperience would help me to establish professionalnetworks that will go a long way in carrying out research inthis interdisciplinary field. I am confident this experience

will provide a rare chance to enrich myself culturally andprofessionally.

0 5 10 15 20 25 30 35 40

6.2

6.4

6.6

6.8

7.0

7.2

7.4

7.6

7.8

8.0

      p        H

Number of days

 B4 Isolates

 Control

0 5 10 15 20 25 30 35 40-0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

   O   p   t   i   c   a   l   D   e   n   s   i   t  y   (    6

   0   0   n   m   )

Number of days

 B4 Isolate

 Control

  Fig.1: a) pH profile b) Growth profile in S4 microbe 

10 20 30 40 50 60 70 80 90

50

100

150

200

250

CIm

Im

Im

Im

C

CCC

C

C

         I      n        t      e      n

      s         i        t      y

         (      c      o      u      n        t        /      s      e      c      o      n        d         )

Position( 2    ) 

Im: Impurity

C: Calcite

C

  Fig 2: XRD analysis of microbial precipitate