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 the

optode, R is the ratio at a certain [O2], R0 is

ratio at anoxia, Ksv2=0, and Ksv1 is the slope

of the line R0/R vs [O2]