Distribution of Algal Photosynthates As Seen
Using Planar OptodesAllison Gregg
3/5/11
Background on Coral-Algal Interactions
Coral reefs filled with great diversity of organisms
Corals around the world are succumbing to environmental stressors
How is algae playing a part?
Top:http://www.sciencedaily.com/releases/2009/03/090320164659.htmBottom: http://www.nytimes.com/2008/01/08/science/earth/08obalga.html
What is Really Going On? Microprobes have shown
that coral-algae interaction zones are hypoxic
Leads to coral disease What is the mechanism
behind this?-microbe mediated?-or something else?
Planar optodes as a way to visualize what is happening Jennifer Smith, http://www.nceas.ucsb.edu/~jsmith/JenniferSmith-Research.htm
What Are Planar Optodes? a type of optical
sensor used for visualizing various analyte concentrations
Able to visualize two dimensional space as opposed to electrodes
used for O2 ,CO2, pH, temperature
~2 cm
^Oxygen bubbled water^
^Nitrogen bubbled water^
How Do Oxygen Optodes Work?
Oxygen optode is made from a cocktail consisting of PtOEP indicator and coumarin antenna dye, immobilized in a polystyrene matrix
PtOEP signal is chemically dependent on analyte concentration; coumarin signal is independent of analyte
Analyte concentration calculated from ratio of fluorescence intensity of indicator: antenna
Experimental Design Original Hypothesis:
Increase of flow leads to increased rates of photosynthesis in coral and macro algae
First, turf algae was placed in a chamber with no flow to determine baseline measurements of photosynthesis
What we found was surprising…
Algae After Being Exposed to Light for Two Hours:
Would We Get the Same Outcome with Flow?
Macro algae was put in front of optode sheet too see how oxygen was distributed in response to flow
Was there more diffusion through environment?
When a Photosynthesizing Algae is Exposed to Flow
What Does This Mean? Oxygen released from algae during
photosynthesis in discrete region- no diffusion Respiration of algae from all around surrounding
area New Hypothesis: The distinct oxygen
gradients produced from algae suggest that the position of coral to algae relative to direction of flow could play a part in the hypoxia along an interface.
The Next Step Does this pattern of distribution occur in other
algae species or coral? Glucose optode to see if DOC is released in
same pattern as oxygen Field work to see if these patterns at interaction
zones can be seen in situ Can a relationship between prevalence of coral
disease and positioning of algae up current or down current from coral be found?
Acknowledgements Thanks to:
Forest Rohwer Rohwer Labbies Andi Haas Morten Larsen Ronnie Glud Sergey Borisov Jen Smith Mark Hatay Peter Salamon Anca Segall Undergraduate Biomath
group
Funding: NSF-funded STEM
Scholarship National Science
Foundation
Ratio to Concentration Ratio= (R-G)/G This ratio is then used to determine the
concentration using the Stern-Volmer equation: C= (R0-R)/(Ksv(R0-R*)
How Does Math Come into Play?
Actual concentration of oxygen is determined by using the modified Stern-Volmer equation:- R/R0=(f/1+Ksv1[O2] + (f-1)/ 1+Ksv2[O2])Where f is the unquenchable fraction of theoptode, R is the ratio at a certain [O2], R0 isratio at anoxia, Ksv2=0, and Ksv1 is the slopeof the line R0/R vs [O2]