New Article: Photosynthesis and the Reef Aquarium, Part I: Carbon Sources

Randy Holmes-Farley · 10/07/2006, 07:08 AM

My next Reefkeeping article posted today:

Photosynthesis and the Reef Aquarium Part I: Carbon Sources
http://reefkeeping.com/issues/2006-10/rhf/index.php

the contents:

Introduction
Carbon Dioxide in Seawater
Obtaining Carbon Dioxide as Carbon Dioxide: Passive Uptake
Obtaining Carbon Dioxide: Concentrating Mechanisms
Obtaining Carbon Dioxide as Carbon Dioxide: Active Transport
Obtaining Carbon Dioxide from Bicarbonate: Carbonic Anhydrase
Obtaining Carbon Dioxide from Bicarbonate: Direct Uptake
Obtaining Carbon Dioxide from Bicarbonate: Proton Pumping
Photosynthesis of Macroalgae as a Function of pH
Photosynthesis of Algae Relative to Their Natural Environment
Photosynthesis of Algae in Continuous Light vs. Light/Dark Cycles
Implications for Reef Aquarium Husbandry
Summary
References

boxfishpooalot · 10/08/2006, 06:45 AM

Wow, its about time sombodys writing about macroalgae chemistry!

Great article Randy!

How many part series?

I particularly found this interesting "The rates of photosynthesis were nearly twice as high with light/dark cycles as with continuous lighting. In two of the species (S. costatum and E. huxleyi), but not the third, the contribution of bicarbonate to the total carbon uptake increased dramatically in light/dark cycles compared to continuous light"

Maybee a dark cycle is important for maximum plant growth?

Im going to try a dark cycle and see how it works for chaeto. Whats the purpose of releasing Co2 when dark? I notice that in one of my experiment tanks, caulerpa raecemosa grows even over night.

Randy Holmes-Farley · 10/08/2006, 08:09 AM

[B]Great article Randy![?B]

Thanks.

How many part series?

Not sure. I haven't written any others yet.

Maybee a dark cycle is important for maximum plant growth?

I too changed my refugia to have a dark cycle when I read this.

Boomer · 10/08/2006, 11:43 AM

You are getting fancier with your articles, i.e., diagrams, molecules etc.. I like that

I see a pC-pH diagram that is a first IIRC

Some questions though ?

1. The pC-pH diagram. The CO2 and CO3-- are falttened out way to quickly . ~7.4 and ~ 6.8. How come ?

2. pKa1 @ 5.85. How did you get it that low? It is normally 6.1. Or is that the full blown all corrected Millero ones ? Same for pka2 = 9.1 all at SSTP. Or is it they are not at 25 C ? Your older artiicles show 6 and 9. Maybe these you just gave are pHnsw corrected for "real " pH NSW. (Millero). IIRC I did them long ago and they were what you gave, 5.85 and 8.92

I'm not at home with my books to look them up

Randy Holmes-Farley · 10/08/2006, 12:24 PM

Yes, the very top of the white curve and the very bottom of the black curve are not exactly right. The equations to solve that are more complicated that then simple ones I was using, and I ran out of time. I don't think the difference is too great, just a funny look to the curve shape. Millero give the same graphs in "Chemical Oceanography" second edition, and they look about the same with less data points but smoother curve fitting.

I also got the pKa values from his Table 7.4 on page 250 of the same book. They are for 35 ppt and 25 deg C.

Boomer · 10/08/2006, 08:05 PM

No it is no that big a deal, CO2 zeros out at the pkaNSW 8.92 and CO3-- at pKaNSW 5.85.

The pKa 's you gave are correct and are the new pHNSW and not the ones I gave, which are pHNBS I have pKa2NSW in my writing calculator but some how I deleted the pKa1. Odd thing is the newest seawater textbooks still use the NBS std, even though it is wrong. The CO2 you gave of .50 mg / l is really close also like 0.47 mg / l. I always just round it off to 0.50 mg / l

pka2NSW = 8.935766688 calculate from Millero 1st edition and he is always changing them

I do not have those curves or tables in my Millero

Seawater pC-pH diagrams, look in your old Spotte 1979

Fig 5-1. I guess yours is really about the same, just thicker lines. Also look at Fig 5-1 my favorite one

Goes with Table 5-1

So no errors on your part......again...

Randy Holmes-Farley · 10/09/2006, 06:23 AM

Thanks, Boomer.

Boomer · 10/09/2006, 10:25 AM

Also look at Fig 5-1 my favorite one Goes with Table 5-1

Fig 2 goes with Table 1. I'm sure you say that. Has all the curves in pC-pH for all the buffers in NSW.

Randy Holmes-Farley · 10/11/2006, 09:53 AM

Thanks, Boomer, I will.

Miggy · 10/15/2006, 01:15 PM

just gonna give my input about light and dark hours.

Plants (algaes) will respirate all day taking in Oxygen and giving out CO2 and photosynthesise for half a day taking in CO2 and giving out Oxygen. so from this if the plant was to have 24 hours of light a day then it would be having to constantly photosynthesise and their would be no balance, so the process would not be working to its optimum level.

Randy Holmes-Farley · 10/15/2006, 01:22 PM

That sounds good, but I could equally well argue that if the goal is as much growth as possible, then the maximum amount of photosynthesis would be desirable, and that arguably comes with 24/7 lighting. Without a comparative test that someone does to show one way or the other, it isn't possible to know for sure what is optimal, and it may actually vary with species of macroalgae.

Miggy · 10/15/2006, 01:33 PM

True, but i think that because it is normally at an equilibrium then if it is photosynthesising 24/ 7 then it will be using twice as much CO2 which may cause the process to slow down considerably.

Randy Holmes-Farley · 10/15/2006, 01:58 PM

If it is using twice as much CO2, then it is necessarily photosynthesizing twice as much.

Miggy · 10/15/2006, 02:12 PM

at first, maybe, but it will not be able to sustain this over a length of time because it will have gone past the optimum working point.

So it may photosynthesise faster at first, but not for very long.

Randy Holmes-Farley · 10/15/2006, 02:14 PM

If that were shown to be true (or not) by experiment, it would be more convincing than an assertion that it will happen.

Miggy · 10/15/2006, 02:19 PM

if i get chance i will conduct an experiment.

Randy Holmes-Farley · 10/15/2006, 02:20 PM

That would be great.

I recentyl added a dark cycle to 3 of my 4 refugia (the fourth already had it), but comparing the growth rates is not easy, and I didn't take any detailed measurements before the switch.

DarkXerox · 10/17/2006, 06:53 AM

Yeah it was interesting to see that the photosynthesis rates differed based on having a light/dark cycle. I think that someone needs to test this possibility with some controls--especially since there are a lot of people out there that have refugia with Caulpera sp. and keep them lit 24/7 in order to keep them from going into a reproductive cycle. I tend to run my Chaetomorphia chamber with 12/12h in order to level out the pH.

Also nice job with all the mechanisms for the creation of carbonic acid, the use of enzymes, and the pKa values for the different equilibria. There actually a lot of us bio/chem people that can understand better when you add that!

However, one paragraph really hit me and it seems to be a recent study (2006). It had to do with the Potassium uptake for a specific species of diatom.

Quote:

The marine diatom Phaeodactylum tricornutum16 was found not only to have an active bicarbonate uptake mechanism, but the researchers further identified at least two different mechanisms. In particular, they showed that part of the uptake depended on the presence of extracellular potassium, and this part of the total carbon dioxide uptake was eliminated when potassium was missing from the medium. A second direct bicarbonate uptake mechanism was independent of potassium, indicating the presence of at least two different pathways for transporting bicarbonate into this organism.

I remember a lot of people that use ZeoVit or some other form of nutrient reduction system, find that they need to supplement K+ in order to maintain colors over time. I assume this has to do with the decreased amount of carbon sources in the water. If I remember from my neuro classes, extracellular K+ levels are often really low at resting potential(such as the area outside of an axon). However since these organisms likely have a minimum of neural tissue, I don't know how this would tie in

But I do know that Na+/K+-ATPase is present in pretty much every cell.

But if one pathway is dependant on K+ concentration, than this supplementation may actually have some sort of foundation to go from. And could be why growth or color may be retarded in some way.

Randy Holmes-Farley · 10/17/2006, 10:17 AM

Also nice job with all the mechanisms

Thanks.

I'm not yet convinced that reef aquaria actually get depleted in potassium (there seems to be conflicting conclusions between tests that use the zeo test kit and data generated by ICP that Ron Shimek posted), but if it did get depleted, such mechanisms might be important as to why potassium matters.

TypicalNoah · 10/26/2006, 08:07 AM

Ahh... This thread makes me very proud. I attend the University of Miami and Dr. Millero will be my Chemical Oceanography professor next semester (or chem o, as we call it). Many of my friends have worked in his lab, and I'm considering changing my majors from marine science & biology to marine science & chemistry.

I'll have to keep reading these involved threads of yours - keep it up!

P.S. Randy, is that molecule in your picture real? And if so, what is it? Some kind of radical or perhaps a transition state? I hope it's not just art. Then I'd feel silly.

Randy Holmes-Farley · 10/26/2006, 08:40 AM

To Reef Central

I've never met Prof. Millero, but I certainly appreciate his books. I hope you enjoy the classes.

The molecule is real. It is phosphate, shown as PO4---. Not only is it important to reefers, but in my real world job it has been my focus for many years. One of my commercial products, Renagel, is a prescription drug that is a phosphate binder that is used in humans. In patients on dialysis, phosphate builds up in the blood unless you use a binder that removes it from food before it can be absorbed. It is detailed here:

www.renagel.com

TypicalNoah · 10/27/2006, 08:51 AM

Heh. Well I feel downright silly. I should have just followed the color red to oxygen and then just... The double bond got me curious. Yeah. Wow. Ha. Er. Transition state... heh.

Thanks for the welcome to reef central. :-D I'll be hopping around the chemistry forum most of the time now.

Randy Holmes-Farley · 10/27/2006, 11:32 AM

Happy Reefing.

192clark · 11/21/2006, 04:36 PM

As to the question of day night cycle. vs 24/7. I think we could take Alaska as an example. Earlier this summer I was there and learned that they have a very short summer but it is quite productive because the night is very short. Therefore more photosynthesis will produce more growth. I belive this is just as good of a test as one can get as it is found in nature.

Randy Holmes-Farley · 11/22/2006, 06:12 AM

It is a good test for the organisms that normally live there, and that live under the nutrient conditions present there. Other conditions and organisms may give different results. For example, if nutrients are limiting algae growth, perhaps lighting above a certain threshold is unimportant for growth. Maybe even the amount of photosynthesis taking place is not limiting.

10/07/2006, 07:08 AM	#1
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	New Article: Photosynthesis and the Reef Aquarium, Part I: Carbon Sources My next Reefkeeping article posted today: Photosynthesis and the Reef Aquarium Part I: Carbon Sources http://reefkeeping.com/issues/2006-10/rhf/index.php the contents: Introduction Carbon Dioxide in Seawater Obtaining Carbon Dioxide as Carbon Dioxide: Passive Uptake Obtaining Carbon Dioxide: Concentrating Mechanisms Obtaining Carbon Dioxide as Carbon Dioxide: Active Transport Obtaining Carbon Dioxide from Bicarbonate: Carbonic Anhydrase Obtaining Carbon Dioxide from Bicarbonate: Direct Uptake Obtaining Carbon Dioxide from Bicarbonate: Proton Pumping Photosynthesis of Macroalgae as a Function of pH Photosynthesis of Algae Relative to Their Natural Environment Photosynthesis of Algae in Continuous Light vs. Light/Dark Cycles Implications for Reef Aquarium Husbandry Summary References __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/08/2006, 06:45 AM	#2
boxfishpooalot Registered Member Join Date: Mar 2005 Location: canada, Grande Praire, Ab Posts: 5,824	Wow, its about time sombodys writing about macroalgae chemistry! Great article Randy! How many part series? I particularly found this interesting "The rates of photosynthesis were nearly twice as high with light/dark cycles as with continuous lighting. In two of the species (S. costatum and E. huxleyi), but not the third, the contribution of bicarbonate to the total carbon uptake increased dramatically in light/dark cycles compared to continuous light" Maybee a dark cycle is important for maximum plant growth? Im going to try a dark cycle and see how it works for chaeto. Whats the purpose of releasing Co2 when dark? I notice that in one of my experiment tanks, caulerpa raecemosa grows even over night. __________________ Its a good idea to have a refrence sample for alk test kits. 1.1350 grams of baking soda in 1gallon of distilled water=10dkh. Check your alkalinity test kit! Algae is Mother Natures phosphate remover Current Tank Info: 220 galon mixed reef. Last edited by boxfishpooalot; 10/08/2006 at 07:08 AM.

10/08/2006, 08:09 AM	#3
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	[B]Great article Randy![?B] Thanks. How many part series? Not sure. I haven't written any others yet. Maybee a dark cycle is important for maximum plant growth? I too changed my refugia to have a dark cycle when I read this. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/08/2006, 12:24 PM	#5
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Yes, the very top of the white curve and the very bottom of the black curve are not exactly right. The equations to solve that are more complicated that then simple ones I was using, and I ran out of time. I don't think the difference is too great, just a funny look to the curve shape. Millero give the same graphs in "Chemical Oceanography" second edition, and they look about the same with less data points but smoother curve fitting. I also got the pKa values from his Table 7.4 on page 250 of the same book. They are for 35 ppt and 25 deg C. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/09/2006, 06:23 AM	#7
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Thanks, Boomer. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/08/2006, 11:43 AM	#4
Boomer Bomb Technician (EOD) Join Date: Aug 2002 Location: Duluth, Minnesota Posts: 11,842	You are getting fancier with your articles, i.e., diagrams, molecules etc.. I like that I see a pC-pH diagram that is a first IIRC Some questions though ? 1. The pC-pH diagram. The CO2 and CO3-- are falttened out way to quickly . ~7.4 and ~ 6.8. How come ? 2. pKa1 @ 5.85. How did you get it that low? It is normally 6.1. Or is that the full blown all corrected Millero ones ? Same for pka2 = 9.1 all at SSTP. Or is it they are not at 25 C ? Your older artiicles show 6 and 9. Maybe these you just gave are pHnsw corrected for "real " pH NSW. (Millero). IIRC I did them long ago and they were what you gave, 5.85 and 8.92 I'm not at home with my books to look them up

10/08/2006, 08:05 PM	#6
Boomer Bomb Technician (EOD) Join Date: Aug 2002 Location: Duluth, Minnesota Posts: 11,842	No it is no that big a deal, CO2 zeros out at the pkaNSW 8.92 and CO3-- at pKaNSW 5.85. The pKa 's you gave are correct and are the new pHNSW and not the ones I gave, which are pHNBS I have pKa2NSW in my writing calculator but some how I deleted the pKa1. Odd thing is the newest seawater textbooks still use the NBS std, even though it is wrong. The CO2 you gave of .50 mg / l is really close also like 0.47 mg / l. I always just round it off to 0.50 mg / l pka2NSW = 8.935766688 calculate from Millero 1st edition and he is always changing them I do not have those curves or tables in my Millero Seawater pC-pH diagrams, look in your old Spotte 1979 Fig 5-1. I guess yours is really about the same, just thicker lines. Also look at Fig 5-1 my favorite one Goes with Table 5-1 So no errors on your part......again...

10/09/2006, 10:25 AM	#8
Boomer Bomb Technician (EOD) Join Date: Aug 2002 Location: Duluth, Minnesota Posts: 11,842	Also look at Fig 5-1 my favorite one Goes with Table 5-1 Fig 2 goes with Table 1. I'm sure you say that. Has all the curves in pC-pH for all the buffers in NSW. __________________ If you See Me Running You Better Catch-Up Seawater Chemistry, Geology, ID Marine Life, Collecting Science Books, Explosives Technology, Audiophile An explosion can be defined as a loud noise, accompanied by the sudden going away of things, from a place where they use to be.

10/11/2006, 09:53 AM	#9
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Thanks, Boomer, I will. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/15/2006, 01:15 PM	#10
Miggy Registered Member Join Date: Nov 2005 Location: Leicestershire, England Posts: 29	just gonna give my input about light and dark hours. Plants (algaes) will respirate all day taking in Oxygen and giving out CO2 and photosynthesise for half a day taking in CO2 and giving out Oxygen. so from this if the plant was to have 24 hours of light a day then it would be having to constantly photosynthesise and their would be no balance, so the process would not be working to its optimum level.

10/15/2006, 01:22 PM	#11
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	That sounds good, but I could equally well argue that if the goal is as much growth as possible, then the maximum amount of photosynthesis would be desirable, and that arguably comes with 24/7 lighting. Without a comparative test that someone does to show one way or the other, it isn't possible to know for sure what is optimal, and it may actually vary with species of macroalgae. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/15/2006, 01:33 PM	#12
Miggy Registered Member Join Date: Nov 2005 Location: Leicestershire, England Posts: 29	True, but i think that because it is normally at an equilibrium then if it is photosynthesising 24/ 7 then it will be using twice as much CO2 which may cause the process to slow down considerably.

10/15/2006, 01:58 PM	#13
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	If it is using twice as much CO2, then it is necessarily photosynthesizing twice as much. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/15/2006, 02:12 PM	#14
Miggy Registered Member Join Date: Nov 2005 Location: Leicestershire, England Posts: 29	at first, maybe, but it will not be able to sustain this over a length of time because it will have gone past the optimum working point. So it may photosynthesise faster at first, but not for very long.

10/15/2006, 02:14 PM	#15
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	If that were shown to be true (or not) by experiment, it would be more convincing than an assertion that it will happen. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/15/2006, 02:19 PM	#16
Miggy Registered Member Join Date: Nov 2005 Location: Leicestershire, England Posts: 29	if i get chance i will conduct an experiment.

10/15/2006, 02:20 PM	#17
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	That would be great. I recentyl added a dark cycle to 3 of my 4 refugia (the fourth already had it), but comparing the growth rates is not easy, and I didn't take any detailed measurements before the switch. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/17/2006, 10:17 AM	#19
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Also nice job with all the mechanisms Thanks. I'm not yet convinced that reef aquaria actually get depleted in potassium (there seems to be conflicting conclusions between tests that use the zeo test kit and data generated by ICP that Ron Shimek posted), but if it did get depleted, such mechanisms might be important as to why potassium matters. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/26/2006, 08:07 AM	#20
TypicalNoah Registered Member Join Date: Mar 2006 Location: Massachusetts or Saudi Arabia, depends Posts: 76	Dr. Millero Ahh... This thread makes me very proud. I attend the University of Miami and Dr. Millero will be my Chemical Oceanography professor next semester (or chem o, as we call it). Many of my friends have worked in his lab, and I'm considering changing my majors from marine science & biology to marine science & chemistry. I'll have to keep reading these involved threads of yours - keep it up! P.S. Randy, is that molecule in your picture real? And if so, what is it? Some kind of radical or perhaps a transition state? I hope it's not just art. Then I'd feel silly. __________________ Noah J.D. DesRosiers KAUST, Jeddah, KSA Here's to fish science... and a low future salary. Current Tank Info: 1/2 gallon killifish container, HA

10/26/2006, 08:40 AM	#21
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	*To Reef Central* I've never met Prof. Millero, but I certainly appreciate his books. I hope you enjoy the classes. The molecule is real. It is phosphate, shown as PO4---. Not only is it important to reefers, but in my real world job it has been my focus for many years. One of my commercial products, Renagel, is a prescription drug that is a phosphate binder that is used in humans. In patients on dialysis, phosphate builds up in the blood unless you use a binder that removes it from food before it can be absorbed. It is detailed here: www.renagel.com __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

10/27/2006, 08:51 AM	#22
TypicalNoah Registered Member Join Date: Mar 2006 Location: Massachusetts or Saudi Arabia, depends Posts: 76	Heh. Well I feel downright silly. I should have just followed the color red to oxygen and then just... The double bond got me curious. Yeah. Wow. Ha. Er. Transition state... heh. Thanks for the welcome to reef central. :-D I'll be hopping around the chemistry forum most of the time now. __________________ Noah J.D. DesRosiers KAUST, Jeddah, KSA Here's to fish science... and a low future salary. Current Tank Info: 1/2 gallon killifish container, HA

10/27/2006, 11:32 AM	#23
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Happy Reefing. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

11/21/2006, 04:36 PM	#24
192clark Registered Member Join Date: Dec 2003 Location: Summerville, SC Posts: 635	As to the question of day night cycle. vs 24/7. I think we could take Alaska as an example. Earlier this summer I was there and learned that they have a very short summer but it is quite productive because the night is very short. Therefore more photosynthesis will produce more growth. I belive this is just as good of a test as one can get as it is found in nature.

11/22/2006, 06:12 AM	#25
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	It is a good test for the organisms that normally live there, and that live under the nutrient conditions present there. Other conditions and organisms may give different results. For example, if nutrients are limiting algae growth, perhaps lighting above a certain threshold is unimportant for growth. Maybe even the amount of photosynthesis taking place is not limiting. __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef