Acclimation in Marine Phytoplankton Uriel Aparicio Dr. Allen Milligan
Dec 31, 2015
Mechanism of Light Acclimation in Marine Phytoplankton
Uriel AparicioDr. Allen Milligan
Relevance50% of net photosynthesis of the earth comes from marine phytoplankton.
Primary production is sensitive to climate variability
To understand these changes and to be able to predict future changes we need to understand factors that influences phytoplankton growth. Example: limiting nutrients
BackgroundFluorescence can be used to indicate physiological status of the phytoplankton. example: high fluorescence=iron limited phytoplankton
In 2002, NASA launched its AQUA satellite with MODIS(MODerate-resolution
Imaging Spectroradiometer).
MODIS is an instrument that can measure the fluorescence of marine phytoplankton.
Background
Fluor
Absorb Light~Incident Light
Fluor~Absorbed Light?
NO!
Fluorescence saturates
Why?
Energy is being lost to some other pathway
Energy Pathways
Photochemistry
Fluorescence
Non-Photochemical quenching (NPQ)
Light availability and nutrient stress can have an effect on the fluorescence through NPQ
Low light acclimated cells have more chlorophyll than high light acclimated cells and therefore absorb more energy. (Greater NPQ)
To detect nutrient stress, fluorescence must be corrected for light dependent NPQ response
So far the corrections to fluorescence data have assumed a single photoacclimation state
Objective
Test NPQ response of phytoplankton under different light conditions
Hypothesis
Low light acclimated cells will demonstrate a stronger NPQ response than the high light acclimated cell.
Low light acclimated cells have more chlorophyll and therefore absorb more energy when they are at the surface.
Methodology
Methodology
Measure the natural fluorescence
Measure the NPQ
Fluorescence Yield
High acclimated cells have a greater fluorescence yield than the low acclimated cells.
NPQ Measurements
(Fm-Fm’)/Fm’
Averaged the last 4 data points
Results
Low Light Acclimated NPQ: 0.69
High Light Acclimated NPQ: 0.35
Prior research has concluded the opposite of our research(Garcia-Mendoza and Colombo-Pallotta 2007; Niyogi et al. 1997a)
These studies (and others) acclimated their organisms to high and low constant light
Maps derived from Satellite Data
Acknowledgements
Howard Hughes Medical Institute
NASA
Dr. Allen Milligan
Dr. Michael Behrenfeld
Dr. Kevin Ahern
BackgroundGlobal climate change can change the availability of nutrients that are limiting in the ocean
Previous studies have been done on iron limitation in the ocean but are limited to bottles or iron addition to surface water.
New techniques with satellites can cover the entire ocean by measuring fluorescence of phytoplankton.
The amount of fluorescence emitted indicates the physiological state of the phytoplankton
Hypothesis
A. NPQ is perfectly efficient at dissipating light energy
B. Fluorescence yield is dependent on the ratio of PSII : PSI
C. Fluorescence yield is dependent on the photoacclimation state
φ
iPAR