Oxygen
An important and highly dynamic water constituent in aquatic ecosystems
Dr Matthew Adams, School of Chemical Engineering
UQ Water Forum, August 18-19 2015
Sustainable Water Program @ the Global Change Institute
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Research question
Water column
Oxygen flux
Seagrass community
Image courtesy of Angus Ferguson (NSW OEH)
Rheuban et al. (2014)
Question: Why does this happen?
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How I explored the research question…
A combination of experimental data and mathematical models:
Experimental data
 Oxygen exchange, light and temperature measured at 3
depths within a seagrass meadow in Lake Macquarie,
New South Wales.
 Measured every 5-10 minutes for 24 hours.
Mathematical models
2 causes
x 2 responses = 4 potential mechanisms
Light history
Gross primary production
Oxygen flux
Temperature
Respiration
Image courtesy of Angus Ferguson (NSW OEH)
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What I found…
Models tested
 Temperature variation
 Light history-dependent gross primary production
 Light history-dependent respiration
X Not sufficiently large. (Knocks out 2 models)
X Cannot explain night-time variation in oxygen flux.
 Fits all data, including night-time.
Light history-dependent respiration importantly contributes to oxygen dynamics in seagrass ecosystems.
Further study is required to fully understand its impacts on ecosystem health.
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What next?
Investigate physical reasons for the source of the “light history-dependent respiration”
that affects the oxygen flux:
Seagrass produces
dissolved organic
carbon (DOC)
(1)
Light
(2)
Daily rhythm in seagrass respiration
Heterotrophic respiration
(until DOC pool
is depleted)
This approach can be used to mathematically model light history,
or acclimation kinetics in response to any external environmental factor,
in any aquatic ecosystem:
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Contact details:
Dr Matthew Adams
Ph: +61 7 3365 3687
Email: [email protected]
Web: http://researchers.uq.edu.au/researcher/3058
References:
Adams, M. P., Ferguson, A. J. P., Maxwell, P. S., Lawson, B. A. J.,
Samper-Villarreal, J. & O’Brien, K. R. Light history-dependent
respiration explains the hysteresis in the daily ecosystem metabolism
of seagrass (submitted).
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