Bioluminescence in P. lunula

[deleted-32471]

I currently in the midst of a science products in which I observe and analyze the bioluminescence of P. lunula, a type of marine plankton. I am going to place tubes of these cultures in boxes, one in total darkness 24x7, one in total light 24x7, and one in darkness for 12hours and light for 12 hours. My experiment guidelines tell me to use a fluorescent light, but im not completely sure why I have to use that. Can you explain to me why fluorescent lights are used in this project? Can I use regular halogen lights?
Thanks

[donnahardy2]

Hi,

I think you are doing this project from the science buddies website. This is a great project.

https://www.sciencebuddies.org/science- ... p033.shtml

Dinoflagellates like P. lunula have circadian rhythms and produce light at different intensities during different times of the day. I have not worked with this organism, but the following report seems to indicate that the bioluminescence is produced primarily during hours of dark. The experimenters keep the cultures exposed to 12 hours of light during the night and 12 hours of dark during the day time so they could do their experiments during the day.

http://www.assurecontrols.com/pdfs/Biol ... Lapota.pdf

The following paper also used cultures in the dark:

http://www.ncbi.nlm.nih.gov/pmc/article ... pdf/96.pdf

I could not find any information that would suggest there is a difference between results of fluorescent or halogen lamps. However, it is important to keep the temperature constant when doing experiments, unless this is your independent variable, and halogen light might heat up the sample compared to the sample in the dark.

Good luck on your project!

Donna Hardy

[aelin]

Hi,

Donna's answer basically covers anything, so I just have a small thing to add on top of it. I did a related experiment using photosynthetic Synechococcus bacteria, so the light source was pretty clearly important. I don't think there is necessarily any substantial difference between the types of lamp; the key thing to look for is the power/area (in addition to the heat, which Donna mentioned. The 'color' of the light may make a difference, but that would be hard to judge without measuring). By this, I mean that you have to consider the intensity of the light reaching the plankton. Halogen lights tend to be brighter than regular incandescent ones, so on a lot of the boxes that come with halogen lights, they will tell you the actual kower (in watts) as well as the power of an equivalently bright incandescent bulb. So, Keep in mind that if you use a halogen bulb and do not know the equivalent power of an equally bright incandescent one, you will have to do a bit of tricky calculation to figure out the distance away from the plankton that the bulb needs to be placed to receive an equal amount of light (remember that the intensity of light varies inversely with the square of the distance, and this is pretty close to accurate).

Hope this helps!
Aaron Lin