Download The Role of the Bacterioneuston in Air

The Role of the
Bacterioneuston in
Air-Sea Gas Exchange
Emma Harrison
University of Newcastle-upon-Tyne, UK
Bacterioneuston??
Sea Surface Microlayer
• Widespread, unique and dynamic habitat
covering ~70% of the Earth’s surface
• Microlayer ranges between 1 – 1000 μm
• Definition highly debatable
• Rich and diverse community of
microorganisms which thrive on the
interaction between the atmosphere and
the water column
Extreme Environment?
?
?
Bacterioneuston
• Bacteria tolerant to this extreme environment
• Estimated that the bacteria present in the
bacterioneuston are 103 - 105 more abundant when
compared to subsurface waters
• Preliminary data obtained from North Sea, UK, has
suggested bacterioneuston dominated by;
- Vibrio sp
- Pseudoalteromonas sp
BUT
• This is not necessarily the case everywhere!
Why is the
bacterioneuston
important?
Interactions with the Air-Sea
Boundary
•
Many exchanges take
place across the
air-sea boundary
•
The interface between
the microlayer and the
atmosphere is 1000 µm
of the sea surface and
50-500 µm of the
atmosphere
•
Consequently, effects of
this boundary on
air-sea gas fluxes of
GREENHOUSE GASES
could be considerable
Microbial metabolism of climatically active trace gases
such as CH4, N2O, CO, DMS and methyl halides in the
bacterioneuston may exert important controls on
air-sea gas exchange
Determining the diversity, abundance and activity of the
major groups of microorganisms in the
bacterioneuston and their involvement in trace gas
cycling are a high priority in the UK SOLAS projects
Research Aims
Specific objectives;
1. To determine the bacterial community structure of
the bacterioneuston with specific reference to
bacteria that metabolise trace gases
2. Investigate the role of the microbial populations on
gas exchange rates in controlled laboratory gas
exchange tank experiments
3. To measure rates of invasive (i.e. air to water) and
evasive (i.e. water to air) air-sea exchange of
selected atmospheric trace gases
•
Project in collaboration with Warwick University, UK
Objective One
“Analysis of the bacterial community structure of the bacterioneuston”
• Bacterioneuston sampled by sterile, polycarbonate
filters
• Removes the top layer of water from the interface
through surface tension
• Construct gene libraries representative of the
microbial community by use of 16S rRNA sequence
data
• Application of PCR and DGGE allows the study of
these complex communities
• Overcomes;
- small sample size
- poor culturability of neuston bacteria
Acquiring Bacterioneuston
Samples
Sampling at Blyth Harbour, North East England
Microbial Community Structure From
Blyth Harbour
Microbial Community Structure From Blyth
Harbour
•
•
Bacterial community structure in the microlayer is distinct when compared to
the subsurface waters
This is also true for Archaea and Eukarya
Objective Two
“Roles of the bacterioneuston investigated through gas exchange tank”
•
Purpose built gas
exchange tank
•
Closed system
•
The microbial community
structure will be
correlated with changes
in the gas exchange rates
•
Conditions altered and
experiments will use local
seawater (North Sea),
river water (River Tyne),
Milli-RO and artificial
seawater prepared in
Milli-RO
Objective Three
“Measure the invasive and evasive rates of atmospheric trace gases”
• Coupling of two gas
chromatographs with gas tank
to create a fully automated
system to measure CH4, CO,
N2O and SF6 concurrently
• Tank headspace circulated
through gas chromatographs
• Gas fluxes quantified by
estimating their transfer
velocities, kw
• Estimate kw by measuring
evasion rates of inert volatile
tracer, SF6 with Schmidt
number based scaling for
each individual trace gas
Conclusion
• Knowledge of the biology and population structure
within the bacterioneuston is still in its infancy
• Unclear what role these microorganisms play
• Is clear the sea surface microlayer has the
potential to impact the cycling of reactive trace
gases and the exchange rate of these gases across
the air-sea boundary
• Using a combination of molecular ecology techniques
and an understanding of gas exchange, the
knowledge of this unique and dynamic environment
will be greatly improved
Acknowledgements
Many thanks to the following…
• Supervisors;
Rob Upstill-Goddard (University of Newcastle)
Colin Murrell (University of Warwick)
• Michael Cunliffe (University of Warwick) for his support
and advice on molecular ecology and for microbial
community structure work
• Grant Forster for technical assistance
• UK SOLAS Project
• Natural Environment Research Council, UK