Science Buddies: "Ask an Expert"

My son is testing the effect of light exposure on bioluminescent dinoflagellates and their circadian rhythm, similar to project described on Science Buddies website.

Three groups of specimens:
1) Group 1, control group, kept in light and dark
2) Group 2, kept in constant light
3) Group 3, kept in constant darkness


He is observing the degree of boiluminescence of each group twice a day, once during "AM hours" and once during "PM hours".

He noticed the following:
1) Control (Group 1) is following expected rhythm of strong bioluminescence during "PM" hours
2) Group 2 (constant light) is producing strong bioluminescence in the AM and PM for TEN DAYS and counting.
3) Group 3 (constant darkness) is also producing strong bioluminescence in the AM and PM for TEN DAYS and counting. Slightly brighter during "AM hours" and now they appear to be fading completely on days 11 and 12.

Questions:
a) What is going on with Group 2 (constant light) and Group 3 (constant darkness) / How can the results be explained?
b) He hypothesized that Groups 2 and 3 would die out/stop glowing, but they are still going! Should he keep measuring for a few more days?
c) Lastly, what camera can be used to photograph bioluminescence?

Thank you.

[Administrator added: URL for Science Buddies project: https://www.sciencebuddies.org/science- ... p033.shtml]

Hello there,

If I am understanding this correctly, you would probably expect Group 2 (constant light exposure) to never produce bioluminescence, while Group 3 (constant darkness) should produce bioluminescence all the time, right? For your control group (Group 1), do you also see bioluminescence during daytime hours? In the produces provided by Science Buddies, they said to rank the brightness of the bioluminescence at your different time points. Would you say that your Group 1 during daytime hours produced any bioluminescence at all, or are they just not emitting any light? Whatever levels of bioluminescence that Group 1 is producing should serve as your baseline when you compare the bioluminescence levels of the other two groups. Hence, when you look at Group 3, do you see higher levels of bioluminescence during the day compared to Group 1, and that the levels should be relatively the same between Group 1 and 3 during the night? If that is what you observe, that should be what you would expect with Group 3 right? So I'm slightly confused as to why you thought your observations of Group 3 were weird.

It is interesting, however, that Group 2 is producing strong bioluminescence at all times even though technically they shouldn't be, according to your hypothesis. How brightly are they glowing compared to Group 1? If Group 2 at all times is glowing as much as Group 1 during the day, then that should be fine because that should be the baseline levels of bioluminescence that the organisms are producing. However, if they are glowing brighter than Group 1, then that is a little strange. Perhaps the organisms have been experiencing other types of stress in your system that you weren't aware of, and that is causing them to glow all the time?

As for why the organisms haven't been dying or not glowing anymore after your last timepoint, I would suggest researching some information about how long these organisms typically live and how long do they usually remain glowing. I'm not too familiar with imaging bioluminescence, so other experts, if you have any idea on how to do this and additional comments on the other questions, please share.

Hope that helped!

Best,
Connie

Thank you, Connie!

To briefly answer your questions, the Dark and Light groups were consistently and equally bright on most days for both AM and PM readings. The Dark group faded altogether near the end of the experiment.
My son guessed that both gruops would be off their typical rhythm but didn't think they would be able to emit light at all after a few days - which wasn't the case!