Timeline for How deep underwater can red photosynthesis work?
Current License: CC BY-SA 4.0
17 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 18, 2023 at 21:50 | vote | accept | Atlas the Worldbuilder | ||
| Aug 14, 2023 at 16:29 | comment | added | Atlas the Worldbuilder | I just wanna say, I hope y’all can find some fun data to help me out! I didn’t expect my question to start such intense debate. 030 | |
| Aug 14, 2023 at 1:33 | history | edited | JBH | CC BY-SA 4.0 |
added 798 characters in body
|
| Aug 14, 2023 at 1:25 | comment | added | JBH | @AlexP I'm finding some of that as I continue with my research, but I'm having trouble seeing past all the environmental research about dead zones (important to humanity, not important to the OP's question). However, the note about max phytoplankton density being 10-15 meters deep either completely underscores my frame challenge (both spectra are strong at that level) or masks a possible reality that we can't trivially codify photosynthesis as "green"... or, that it's hard to separate photosynthesis from the other aspects of life such as nutrient supply, which drops by depth. | |
| Aug 14, 2023 at 1:15 | comment | added | AlexP | Re: where would we find photosynthetic life in the ocean. On Earth, phytoplankton density is maximum between 10 and 15 meters deep, and compensation depth (= depth where net growth rate of phytoplankton is zero, less than 1% of solar light penetrates) is about 100 meters. | |
| Aug 14, 2023 at 1:03 | comment | added | JBH | @AlexP The debate between myself and Erik is exposing useful questions that will help the OP. When you say "very much more transparent" you're not wrong, but how significant is it? A correction to Erik's graphs demonstrates that the significance changes depending on where you are in the ocean and as yet neither of us have answered the question, "where would we find photosynthetic life in the ocean?" The OP's simple question is "how deep does red go?" but I'm unconvinced that my frame challenge, "it doesn't matter," is wrong. | |
| Aug 14, 2023 at 0:59 | history | edited | JBH | CC BY-SA 4.0 |
added 612 characters in body
|
| Aug 14, 2023 at 0:45 | comment | added | AlexP | There is no such thing as a perfectly transparent material which is not a hard vacuum. Three kilometers of the best optical glass will be completely opaque. Many substances, such as glass or water, are much more transparent to certain wavelengths than to other wavelengths. Unlike wavelengths commonly used for communications which are attenuated to nothingness extremely quickly, water happens to be transparent in the visible spectrum, but it is very much more transparent to blue than to red. (Excellent diagram here.) | |
| Aug 14, 2023 at 0:35 | history | edited | JBH | CC BY-SA 4.0 |
added 1780 characters in body
|
| Aug 14, 2023 at 0:20 | comment | added | JBH | ... electromagnetic waves for communication, so they're looking at much longer transmission distances than 3.6km (ocean average depth). I'll update my answer to repair the weakness, but it's far from giving Erik the ability to say, "you're wrong!" | |
| Aug 14, 2023 at 0:19 | comment | added | JBH | @jb6330 I appreciate you're digging deeper into this! But you're suffering from the same problem Erik is. What's "significant?" I looked at the absorption chart from Wikipedia and dismissed it as valueless due to its use of a logarithmic scale. It makes the absorption lines look more significant than they are. Across the entire average depth of the ocean the window that is meaningful for red/green spectra is only 5% and across it's width it's a mere fraction of that. Now, that is a weakness in my answer - the articles are talking about the use of ... (*Continued*) | |
| Aug 13, 2023 at 5:19 | comment | added | jb6330 | I dug a bit further. Wikipedia has a nice chart based on data from a compendium of dozens of papers on the optical absorption of water. | |
| Aug 13, 2023 at 5:08 | comment | added | jb6330 | Considering how narrow emission/absorption spectra can be, I don't trust this extrapolation to hold. The fact that red light is absorbed first first seems to be common knowledge covered in introductory materials. | |
| Aug 12, 2023 at 23:55 | comment | added | ErikHall | Just the heads up, in case you dont get notified about the @ thing, i disagree with your answer. | |
| Aug 12, 2023 at 12:04 | comment | added | AlexP | "The difference in permittivity between the red and green spectra is, for the intent of your question, zero": I don't know about this permittivity thing, but in water red light is attenuated about 100 times more strongly than blue light. Just ask anybody who has ever tried to take a photograph or make a movie under water. Without compensating filters, ten meters down everything is blue-green. (Water, like many substances, has windows where it is much transparent than at other locations in the electromagnetic spectrum.) | |
| Aug 12, 2023 at 10:28 | comment | added | Atlas the Worldbuilder | I admit, it’s not every day that I simultaneously A) learn a new thing about the Stack Exchange, B) learn a new word, C) receive such an eloquent response to a scientific query, and D) have said response prompt me to re-assess the whole issue from a new perspective! Thank you so much for your analysis! 030 | |
| Aug 12, 2023 at 5:02 | history | answered | JBH | CC BY-SA 4.0 |
