Science Buddies: "Ask an Expert"

Hello!
Working on helping my sister set up her science fair project using dinoflagellates. We bought a photometer to measure the brightness, but the photometer can't pick up the brightness that the dinoflagellates are producing. We read that you can make your own brightness scale, but how exactly do you do that? What is your frame of reference for the brightness levels? It seems very imprecise. Is there another way to measure brightness? Or another way to measure the health of the dinoflagellates that doesn't directly measure the brightness? Also, how would you determine if the brightness levels are different because of dinoflagellates dying in the test tube vs. dinoflagellates living but producing less light? Thank you in advance for your help!

Hi,

Your questions and reasoning are all good. The relative brightness scale is pretty arbitrary and a photometer would certainly be the best way to measure the glow. Have you tried using an app on a smart phone to measure the light intensity? I know there are several apps available for both iphones and androids but I have never used one to measure bioluminescence from dinoflagellates. I just did a search for this and found some promising hits:

Smartphone-based low light detection for bioluminescence application
https://www.nature.com/articles/srep40203

If you have to use the light range measurement by eye I would suggest diluting the cultures to get a range of brightness from low to high. If your camera has a way to control the shutter then you can take photos of the glow at various shutter speeds until you find one that gives a good image--bright enough to see easily but not so bright as to be washed out. You will have to set up the camera or phone on a stand or tripod and probably leave the shutter open for several seconds to get a good exposure. Just experiment with different camera settings until you find one that works for the range of glows that you see.

In response to your last question about how to tell the difference between dead dino's and ones that just aren't putting out the light, I don't have an easy answer. Here's a link to a Research Gate query from a user who wanted to know how to determine viability of marine algae: https://www.researchgate.net/post/Dyes_ ... microalgae

If you have a microscope with a magnification of 400X, you can examine the dino's to see if they look healthy and you can do a rough cell count per field so you can at least know about how many dino cells are in your culture. This is not really a scientific test to distinguish live from dead cells, but it may be the best you can do.

I hope this helps. Please post again if you have questions.

Good luck!

Sybee

Thank you very much for your help! I am going to look in to your suggestions!

You are most welcome. Glad to help. If you have any more questions, please don't hesitate to post again.

Sybee