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Oxygen saturation/Temperature/Pearling

Discussion in 'Are you new to aquatic plants? Start here' started by chris81, Mar 31, 2010.

  1. chris81

    chris81 Prolific Poster

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    Hi Guys,

    Today after having performed a water change and dosed ferts as usual i increased my aquarium temperature from 20 to 22 degrees. After some hrs plants started to pearl much more than usual. In view that the only parameter i changed was temperature am i right to assume that pearling is temperature dependent?

    If so would it be mostly because photosynthesis increases with increase in temperature or because oxygen saturation levels decrease with temperature?? Or rather a direct effect of both??

    Just curious!

    Thanks
     
  2. Left C

    Left C Lifetime Members
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    This part of your question is in reverse. Cooler water can store more O2 than warmer water.

    Oxygen Saturation vs Temperature
    : http://users.vcnet.com/rrenshaw/do.html

    [​IMG]
     
  3. Biollante

    Biollante Lifetime Charter Member
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    Pearling Is Not Temperature Dependent

    Hi,

    As Left C has shown the same amount of Oxygen in terms of parts per million may not be at saturation point at a lower temperature, but at a higher temperature that may indeed be the saturation point. :confused:

    As confusing as that was I do not think the increase in temperature is the main reason, though it no doubt helped. ;)

    The water change itself tends to saturate the water with Oxygen, as well as add Carbon Dioxide from the air. That it took a couple of hours indicates the plants may have had to produce a fair amount of Oxygen to bring the water to Oxygen saturation. :)

    This may indicate that even after the water change a fairly high level of organic compounds remains, I would recommend another water change in two days. :)

    I do not think the increased temperature increases the rate of photosynthesis in general, particular plant species may do better at one temperature than the other however. :gw

    Therefore, no, pearling is not temperature dependent, technically all pearling proves is the water is Oxygen saturated and photosynthesis is taking place. :cool:

    Biollante
     
    #3 Biollante, Mar 31, 2010
    Last edited by a moderator: Mar 31, 2010
  4. Philosophos

    Philosophos Lifetime Charter Member
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    I don't honestly thing 6ppm vs 12 or even 20 would matter. The percent of space taken up doesn't change significantly, and the entire tank doesn't start pearling from overall saturation.

    Working from pure oxygen at 1psi (12 inches down in a tank) and 80F, we're looking at a density around 1.27mg/cc

    6/1.27=4.7244cc
    12/1.27=9.4488cc
    20/1.27=15.74803149606299cc

    Even at 20ppm, that's only 11% more space taken by oxygen than at 6ppm.

    If anything I'd be looking more towards high O2 levels and supersaturation within localized dead water around the leaf created by the barrier effect of leaves. I would think this to be consistent with the fact that it's fine, densely leaved plants that create pearling best. These complex structures create more resistance (similar to sound baffling) versus a large, flat surface. Even the size of the bubbles seems to inversely correspond with leaf size, and correspond with density.

    If the O2 is simply pushes throughout the tank and saturates evenly, then you'd be seeing "pearling" evenly throughout the tank as you would in supersaturation from a WC.

    The math behind the physics of flow over a complex surface like bryophytes is beyond me, especially considering I don't know what percent of gasses expelled are O2 vs. CO2 from plants. etc. etc. Maybe someone else can expand there.
     
    #4 Philosophos, Mar 31, 2010
    Last edited by a moderator: Mar 31, 2010
  5. Biollante

    Biollante Lifetime Charter Member
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    Not Really

    Hi,

    No wrong track here, Dan.

    Vascular, non-vascular is not the difference. Multiple boundary layers exist, Prantl's is the main plant one that is why Fick's 1st law is so important along with Brownian motion. This is often the confusion of bubbles versus gas in solute.

    Pearling isn't even simply do to different plants different rates and efficiencies in photosynthesis.

    Point of saturation is the point of saturation whether .000001% or 10% more.

    Supersaturation as such is unlikely under aquarium conditions.

    I'll try to come up with a better explanation tomorrow.

    I'm on a little goober device, having a hard time typing and thinking, thinking hurts.:eek:

    Biollante
     
  6. jonny_ftm

    jonny_ftm Guru Class Expert

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    To add to the confusion, increasing temp from 20 to 22°C can accelerate the growth of many aquatic plants that will slow in cold water. Above 26-28°C, many plants will slow down again their growth

    So, in addition to all that was said above (CO2 and O2 concentrations added by the WC), this pearling could be due to the increased growth speed by temperature. Also, Tom encourages often to do these WC under light: during the emersed time, plants receive stronger light while getting tons of CO2 from direct air. That's why, after WC we often see a huge pearling

    So, really many factors play here
     
  7. chris81

    chris81 Prolific Poster

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    Thanks to all..

    I think that jonny_ftm has a point here. I performed nearly a 100 percent water change during which i trimmed glosso and arranged a bit the aquascape so yes plants would have received copious amount of direct lights. I didnt think of that at all and thought that the only changing variable was temperature in this case.

    I have performed 50 percent water changes before and never have the plants pearled as much so i doubt that it was the 02 and co2 from the performed water change.

    Never the less.. Thanks again guys..
     
  8. jonny_ftm

    jonny_ftm Guru Class Expert

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    yes, often we assume that the most evident parameter to our eyes is the responsible of our conclusions. This is true with nutrient x causing algae, intense light for some plants, KH, GH... Many variables are present that it is easy to draw quick conclusions
     
  9. Biollante

    Biollante Lifetime Charter Member
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    Just Forgot To Mention...

    Hi All,

    While I do agree that plants have particular temperatures they grow best I seriously doubt that a two-degree Celsius increase in temperature alone can or does account for such increased pearling.

    For tropical plants, 20 or 22 degrees Celsius is low and would (will) grow at a slow rate, should these be cold-water plants they are fine and a slight increase in temperature can increase growth and therefore pearling, I still reject the idea that temperature increase alone was responsible.

    You state in post #1 that the only parameter you changed was the temperature, concluding that pearling is temperature dependent while I accept that temperature is a factor, it is not the dominant or even a dominant factor.

    To satisfy myself in at least an abtuctive sense that changes in temperature alone over short periods will contribute greatly to pearling. In six tanks including the LoudCreatureWhatSharesMySpace’s beloved Goldfish (GF for Detritus Mulm) tank, I raised the temperatures by two to three degrees Celsius and honestly, I have seen no perceptible difference in pearling. I will increase the temperature by another two degrees, but I do not see enough to cause me to consider expanding the experiment.

    In post #7 you add another set of factors, that normally you do 50% water changes yet this time you did a nearly 100% water change. This adds even more weight to my statement in post #3. One method of providing good CO2 to aquatic plants is 70% or greater water changes every other day. The effectiveness of the water change method increases by splashing or pouring water in over your hand or onto a saucer or such.

    Starting post #7 you state that you “trimmed glosso and arranged a bit the aquascape so yes plants would have received copious amount of direct lights,” at this point you seem to concede that maybe there is another variable or two in play. :rolleyes:

    I would argue that rearranging and trimming and letting more light in, as well as probably increasing circulation are far greater factors than temperature. ;)

    No matter what factors you or anyone else wish to cite, pearling is a function of Oxygen saturated water and photosynthesis, which temperature is certainly a factor, in this case I simply doubt it is the dominant factor. The availability of plant friendly carbon, nutrients and light, above all light drive photosynthesis, Oxygen saturation is what it is at whatever temperature it occurs, mixing water, splashing agitation increases and facilitates the dissolution of gases such as Oxygen and Carbon dioxide into water.

    I wonder is the pearling a great today as yesterday, will it be as great tomorrow? Is the temperature the same? Hmmmm... :confused:

    You are of course welcome to “doubt” whatever you like; the evidence simply does not support your “doubt,” regardless how stridently you “doubt.”

    In post #3, there was no intention to offend. :)

    Biollante
     
  10. Philosophos

    Philosophos Lifetime Charter Member
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    The comparison wasn't so much vascular/non-vascular as physical structure. The surface area on a patch of HC or glosso is far higher than that of any other plant, and I'd be willing it's able to dampen flow better than just about anything else per gram of mass. A lot of the others happen to be bryophytes, but there's glosso as an example too. I'm betting neither of us is going to be able to pop out an accurate set of equations to describe tubulence effect on various species of plants in a timely manner, so I made comments based on observations. I have never seen a broad leaf plant pearl so well as finer plants, and I've also noticed that plants closer to the substrate don't endure as much high flow most of the time. Even in mid-column though, it's been mosses that tend to pearl (subjectively) better than stems near by.

    I'm not completely sure on that one as a matter of raw facts; it's hard to compare when not all species pearl the same way and there's no convenient method of measuring the total quantity of pearling in an objective fashion. I sure don't want to count the little micro bubbles on pearling anubias at least ;)

    Even if we could measure the pearling, we'd have to poke at the equilibriums for tons of other factors to get a concrete answer.

    Based on known principles, I'd say that metabolism obviously differs between plants, so both the citric acid and calvin cycles should produce oxygen and CO2 at different rates that would release in localized areas on the leaf at different rates based on things like the size and density of stomata.

    I realize that saturation can happen at any point, but this is why I added the concept that pearling happens on leaf surfaces, not in the tank as a whole. This would require it to be localized, otherwise our hardscape would "pearl." As such, it indicates that the rate of dissipation through current would have to play some sort of roll.

    I agree for the most part; water changes and CO2 injection would be the only common ones I know. Constant high saturation of air tends to give some fish bloat IME.

    I also agree about temp not being a huge part of it, at least not when speaking of a couple degrees. There are cold water mosses that pearl all day long at 26c and lower.
     
  11. Biollante

    Biollante Lifetime Charter Member
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    Assumptions

    Hi Dan,

    I will try to give a better answer this evening. :)

    A few of my working assumptions. :gw

    First working assumption (if I was or am unclear), the definition of pearling that it is a result of photosynthesis, hence my comments exclude inanimate object or any organism which do not convert light energy to chemical energy and store it in the bonds of sugar (6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2).

    Second working assumption is that different plant species have different requirements and that many factors can and do influence the various rates of photosynthesis.

    Third working assumption is that we are operating at normal planted aquarium under “standard day” sea level conditions unless otherwise noted.

    Fourth working assumption is that I am not very bright and I generalize or tend to answer the question posed. I do not have the fancy calculators and my math is rusty but I think I can explain most of it within reason, I will show my work and you bright boys can clean it up or dispute the results.

    Fifth working assumption is that I cheat when possible. I tend to derive my numbers and formulas when possible from pocket handbooks, which are themselves derivatives other engineering or scientific tables, same goes for trigonometric identities, methods of integration or differentiation and so forth, this stuff may be second nature to you, but I have to work at it, it has been years since I seriously tackled Calculus and differential equations. It will have to be hand written as I do not understand or even know if it is possible to produce the symbols in a post. :eek:

    Biollante
     
  12. Philosophos

    Philosophos Lifetime Charter Member
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    Sounds like we've got all the same presuppositions there.

    Math is something I slave at too. It's possible to produce the symbols on the character map under start/acessories/administrative tools if you do a little work. I cheat as much as you do when I'm not talking nutrient concentrations; plenty of deriving from tables.

    Most of what I'm speaking of with pearling is based on general observations; as I said, I can't measure this stuff. If I had the tools, I'd probably have to spend a while to learn how to use them.

    I guess the only variation is how we view the physics of pearling, and once again it's hard to be objective.
     
  13. chris81

    chris81 Prolific Poster

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    For the record: Pearling rate is still visibly higher.
    For argument's sake: I never stated nor concluded that temperature causes an increase in pearling directly.. I just asked a legitimate question. The only fact here still remains that higher temp decrease oxygen saturation point.. :p
     
  14. Biollante

    Biollante Lifetime Charter Member
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    Dog-Faced Puffer Ate My Report...

    Hi All,

    I apologize I didn’t get my assignment handed in, the dog-faced puffer ate it before I could hit the “submit” button. :eek:

    I had one of those problems this evening that if I were an advanced aquarium keeper I am sure would not have happened. Anyway, I ended up doing a 110% (by volume) on a small (55-gallon) tank, though I turned the temperature down two degrees and the pearling took off like crazy 15 minutes after I finished, so I have changed my mind, since the temperature is the only change I made. That proves that lowering the temperature causes pearling… :rolleyes: Just kidding… about the changing my mind part anyway, the problem was real and so were the results…

    A couple of thoughts (whew, that is painful). :eek:

    I actually dislike the term pearling, it is one of those silly made up words that actually has another meaning.

    Actually measuring the amount of Oxygen produced is relatively easy and rather astonishing.

    Though it may be counter-intuitive, the colder water appears to be better for pearling in general and the first brush research seems to suggest best Oxygen producing plants (Oxygenators?) seem to be cold-water aquatic plants. ;)

    I doubt there is much question about the pearling itself; I suspect that what we will find is that most of the differences in pearling revolve around the differences between species and how much light they are getting. Secondary issues will include water quality, circulation, nutrient and obviously CO2 availability.

    Light will be the single greatest factor.

    As to saturation, remember the vastly greater ease with which CO2 enters solution versus O2. Saturation for CO2 in water is 1.45 grams per liter at 25 C, versus 8.2 mg per liter for O2.

    Generally, we never want CO2 in solution to exceed 40 mg/l; we always want the water to be as close to 8.2 mg/l (at 25 C).

    Fish are not the closed systems you mammals are. If the fish are bloating it is more an issue of diet or osmotic regulation.

    Significant super saturation of oxygen or for that matter, any gas, under aquarium conditions seems unlikely.

    Anyway, I will try again tomorrow. :gw

    Biollante
     
  15. Biollante

    Biollante Lifetime Charter Member
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    Oops! Looks Like I Misunderstood The Term

    Hi Dan,

    On the point of super saturation of oxygen, I took it to be as in the “cooling tower” version, as in explosive almost. :eek:

    I realize the way you meant super saturation (a more reasonable interpretation for our discussion) and I understand your concern. :eek: I have some research information that may be relevant I will share later. ;)

    My bad! :(

    Biollante
     
    #15 Biollante, Apr 3, 2010
    Last edited by a moderator: Apr 3, 2010
  16. DaBub

    DaBub Guru Class Expert

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    the point that plants "pearl" would be the point of O2 saturation caused by photosynthesis and the actual saturation point is on "that plants" surface where the "excess O2" is released. The water in the entire tank does not have to be at saturation. In aquariums that is overall quite well mixed seems that the O2 is overall about the same, but does not have to be.

    You big green sweetie, I'll be by later to help with the math, my hand writing is better. Really boundary layer is not the big issue.

    remember the proof of photosynthesis was holding a willow sprig underwater. Fick's so on is more how the plants get the things to carry on photosynthesis. remember you point out many times it is CO2 in solute not bubbles that provide carbon to plants. Aqueous CO2 is heavier, tends to sink not rise, that is part misunderstanding of Fick's 1st comes in, as you say many like watching the bubbles.

    later,
     
  17. Biollante

    Biollante Lifetime Charter Member
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    Pearling Is, Well, Plants Bubbling

    Hi All,

    Actually, I do not have much more than what DaBub said. :)

    There really is not much mystery involved to the release of the six Oxygen molecules that result from the utterly mysterious process of photosynthesis. If the water cannot absorb, dissolve any more Oxygen, the Oxygen appears as a bubble.

    After reviewing the process of “pearling,” I stand by my previous comments. :)
    Adding for clarification:

    1. I do not think folks really care.
    2. Photosynthesis can take place without pearling.
    3. Even in Oxygen rich water some plants are more efficient than others are.
    4. Dissolved organic compounds will impede “pearling.”
    5. Vascular and non-vascular plants differ how they receive, contain and release gasses.
    6. http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html is a good primer on photosynthesis generally.
    7. Then Tom Barr’s http://www.barrreport.com/showthread.php/349-Barr-report-Newsletter-Light-and-Photosynthesis.
    I appreciate the efforts of DaBub, Randy and Karen in trying to forward my education, anything intelligent that may come out and anything mathematically correct is there doing, anything stupid or incorrect is no doubt mine. I will do threads on boundary layers, and the laminate nature of water and diffusion. As well as Henry’s law with water vapor, layers and partial pressures should make another thread.

    I think “they” may have come up with a nifty surface area calculator for plants, or anything else that has, well, a surface. :eek:

    Biollante
     
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