Laser Spectroscopy on Microbial Mats in a Marsh Environment K.H. Szekielda and Yiping Zhang

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Laser Spectroscopy on Microbial Mats in a Marsh
EnvironmentK.-H. Szekielda and Yiping Zhang 

• Microbial mats represent unique physico-chemical
  micro-environments over a short space scale.
• Photosynthesis occurs only a few millimeters
  above the sediment/water interface where enough
  light is available for primary production.
• The photosynthetic rate is determined by
  diffusion of nutrients from below and above the
  sediment/ water interface.
• Transparency and porosity of the interface are
  important factors.

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MICROBIAL MATS IN SHINNECOCK BAY
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MICROBIAL MATS IN SHINNECOCK BAY
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MICROBIAL MATS IN SHINNECOCK BAYSURFACE OF
TRANSFERED MICROBIAL MATS
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MICROSCOPIC VIEW OF MICROBIAL MAT
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Experimental Setup
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Experimental Condition

• Blue laser l 400 nm, Power 2 mW
• Multimode bifurcated fiber, Core f 200 mm
• Fiber Optic Spectrometer Range 200-850 nm,
  Resolution 1.3 nm, Integration time 2 sec

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FLUORESCENCE OF MICROBIAL MAT
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FLUORESCENCE OF MICROBIAL MAT
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VERTICAL PROFILE (mm) OF FLUORESENCE
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VERTICAL PROFILE (nm) OF FLUORESENCE
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Laser Spectroscopy Results

• Outside the photosynthetic layer (a few mm),
  bacteria determine the biogeochemical and
  respiratory processes.
• The variation of chlorophyll fluorescence peak
  agrees with oxygen microprobe measurements in
  other regions.
• Microscopy of the surface layer show that diatoms
  and cyanobacteria are major organisms responsible
  for the fluorescence.