THE FATE OF MARINE SNOW: EFFECT OF AGGREGATION AND ASSOCIATED BACTERIA ON METHYL IODIDE PRODUCTION'

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THE FATE OF MARINE SNOW EFFECT OF AGGREGATION
AND ASSOCIATED BACTERIA ON METHYL IODIDE
PRODUCTION.

• Noble Asare1,2, Carol Turley2,
• Phillip Nightingale2, Malcolm Nimmo1

1. University of Plymouth, 2. Plymouth
Marine Laboratory
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Layout

• Introduction
• Aims and Objectives
• Sampling site
• Experimental Design
• Result and Discussion
• Summary
• Future Work

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Introduction

• The role of the oceans in regulating
  atmospheric gases
• Halogenated Compounds
• Monohalomethanes (CH3X)
• Methyl Iodide (CH3I)
• Bacterial association with marine aggregates

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Aims and Objectives

• To investigate CH3I production in marine snow
  through controlled laboratory experiments.
• To estimate the amount of CH3I production in
  marine snow and their contribution to sea-air
  flux.
• To assess the role of microbial community
  associated with marine snow in CH3I production.
• To evaluate the effect of aggregation process on
  the rate of change of CH3I concentration in
  seawater.

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Sampling site
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Experimental Design
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Samples (In Dark)
Rolled
Unrolled
Live
Dead
Live
Dead
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Analysis

• Each replicate sample was analysed for
• CH3I concentration with a GC system
• Bacterial leucine incorporation rate
• Bacterial cell enumeration
• Total bacterial cell numbers
• Free bacterial cell numbers

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Result and Discussion
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Result and Discussion
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Result and Discussion
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Relationship between bacterial specific
activities and change in CH3I concentrations over
time.
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Relationships between the rates of bacterial
leucine incorporation and change in CH3I
concentration over time.
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Percentage production of CH3I from bacterial
activity.
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Summary

• Questions
• - Is marine snow a significant source of
  atmospheric methyl iodide?
• - Are microbial community associated with marine
  snow significant contributors to the observed
  methyl iodide production in the marine
  environment?

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Summary

• Observations
• - There was a significant production of methyl
  iodide as a result of bacterial association
  with marine snow
• - Rate of production of methyl iodide was found
  to be enhanced by the process of aggregation

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Summary

• Deductions
• - Marine snow is a significant source of methyl
  iodide from bacterial degradation
• - Rate of formation of aggregates enhance the
  rate at which methyl iodide is produced
• - If the natural marine conditions are similar
  to the experimental conditions, bacterial
  association with marine snow will contribute
  significantly to the total annual flux of methyl
  iodide to the atmosphere

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Future Work

• To investigate if the gross methyl iodide
  production is affected by removal through the
  activity of other bacterial community in the
  experimental medium.
• To develop a method to effectively assay the
  removal of methyl iodide by bacteria in the
  experimental medium.
• To estimate the rate of removal and hence the
  gross production of methyl iodide in the
  experimental medium.
• To assess the seasonality in methyl iodide
  production/consumption in the turbidity maximum
  zone of the Tamar.

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Thank You!