Redfield Ratio Revisited – What are we doing wrong?

[Larry L]

NO3 18.77, PO4 .18

Not sure where the PO4 average of 0.18 comes from. Even using the high end of any value shown as ranges I only come up with an average of 0.094.

 

[Futuretotm]

Not sure where the PO4 average of 0.18 comes from. Even using the high end of any value shown as ranges I only come up with an average of 0.094.

hmm I did it too, intersting, anything we are missing @Mike Paletta

 

[Reef and Dive]

What do they mean ratio below 29? 29 what? Whats the ratio cyano favor?

Nitrogen / Phosphorus ratio. But the main point here is not about specific numbers...

Since we do not have very specific targets, Nitrate / Phosphate ratio serves as a reasonable guide. The older studies actually used that.

My personal belief is not actually to chase a ratio nor specific numbers. Just take them as a guide to understand things. If the reef goes well just forget it.

There goes a practical example:
Nitrates always around 0.5 and phosphates around 0.08. You keep having cyano problems. Phos seems ok but actually a bit unbalanced.
In that case you can lower more your phosphates and maybe considering raising nitrates a bit to get a better ratio (been there and done that). You will see a bit of green algae proliferation with cyano reduction with time...

 

[BAUCE]

here are the "MASTERS" of reefing average numbers:

Alk was 8.19, Ca 419. Mg 1361, NO3 18.77, PO4 .18, Sr 8.6 and temp 77

Masters included are:
Julian Sprung of Two Little Fishes NO3 10-15, PO4 .015
front tank WWC NO3 10-15, PO4 .03-,08
Julian and Cruz of Elegant Corals NO3 5, PO4 .05
Stuart Bertram NO3 15-20, PO4 .046
Jeff Leung NO3 54, PO4 .04
Brad Syphus NO3 20, PO4 .10-.20
Jason Fox NO3 5-10, PO4 .08-.10
Dr. Sanjay No3 20-40, PO4 .12-.22

All credit to @Mike Paletta and this orignal thread at: https://www.reef2reef.com/threads/tank-parameters-of-some-masters.295215/

do those numbers really average out to .18 on po4?

edit: nvm, see that has been adressed

 

[BAUCE]

@PSXerholic you chime in on this thread yet?

 

[BAUCE]

Nitrogen / Phosphorus ratio. But the main point here is not about specific numbers...

Since we do not have very specific targets, Nitrate / Phosphate ratio serves as a reasonable guide. The older studies actually used that.

My personal belief is not actually to chase a ratio nor specific numbers. Just take them as a guide to understand things. If the reef goes well just forget it.

There goes a practical example:
Nitrates always around 0.5 and phosphates around 0.08. You keep having cyano problems. Phos seems ok but actually a bit unbalanced.
In that case you can lower more your phosphates and maybe considering raising nitrates a bit to get a better ratio (been there and done that). You will see a bit of green algae proliferation with cyano reduction with time...

did you hack my apex and see my test results? and my tank? lol my cyano is finally gone because I've increased my nitrate dosing recently. I didnt even realize it was happening because of ratio between these nutients. Cool stuff.

 

[Reef and Dive]

My bold and Nitrate is NO3, Phosphate is PO4

I do not know where you get ppb from - I read @Thales post as it is ppm both values and I do my calculation like this

NO3 molar weight is 14 +3*16 = 62. NO3-N will be 14/62 = 0,225 = 22,5 %
50 ppm NO3 will be 50 * 0.225 = 11.25 ppm as NO3-N
PO4 molar weight is 31+4*16 = 95 P will be 31/95 = 0.326 = 32,6 %
0,91 ppm PO4 will be 0.91*0.326 = 0.296 ppm as PO4-P

11,25/0.296 = 38 N/P ratio



Yes if @Thales meant ppm in his post - your wrong. and only he can thale if its wrong assumption of me or not


Sincerely Lasse

Mr. Lasse, a practical / simple way to convert Nitrate / Phosphate to Nitrogen / Phosphorus ratio is just using this:

Nitrate / Phosphate * 1.53
Just to make it easier for those who want to know the exact ratio...

 

[Reef and Dive]

To enrich the discussion, it is what happened in my fuge in a 2 month period while dosing nitrates raised from 0 to 3 and lowered phosphate from 0.26 to 0.05.

Don’t worry about this algae, there’s none on my display this works as an open ATS...

 

[Lasse]

To enrich the discussion, it is what happened in my fuge in a 2 month period while dosing nitrates raised from 0 to 3 and lowered phosphate from 0.26 to 0.05.

Don’t worry about this algae, there’s none on my display this works as an open ATS...

Did you lost all of your macros? I would not be surprised if the "micro algae" in your pictures in reality are cyanobacteria - not the mat forming type - just an other form.

Sincerely Lasse

 

[Reef and Dive]

Did you lost all of your macros? I would not be surprised if the "micro algae" in your pictures in reality are cyanobacteria - not the mat forming type - just an other form.

Sincerely Lasse

I have checked on the microscope. They are really green algae...

My chaeto died some time ago, so I decided to let the fuge be populated by any green algae and it’s working to keep any algae out of the display, even keeping pH quite stable.

pH track

Tank under sunlight for better algae exposure:

Under LEDs:

 

[Dan_P]

Paulo Mallard Scaldaferri, João Carlos Basso, Marcos Augusto Bizeto, Miguel Mies, Roberto Denadai, Junio Melo

Introduction

Possible applications of the Redfield ratio in the management of the marine aquarium have been discussed over the year. Many have considered that knowledge very helpful while others consider it completely dismissible and useless to the reef keeping hobby. Our objective with this systematic literature review was to obtain the best information that could help clear this concept in terms of aquarium reef keeping.

It has been stated in the past that the well-known 106: 16: 1 carbon : nitrogen : phosphorus ratio should be aimed in order to keep a healthy aquarium. It has been suggested that it would prevent nuisance algae and cyanobacteria by many respected authors like Julian Sprung (1) and João Carlos Basso (2) among others (3). However, many hobbyists have questioned the actual usefulness of these predictions and possible corrections.

Origins

In 1934 Alfred Redfield published a widely known study (4) comparing the rates of oceanic organic compounds collected on the path of the "Dana" ship, between 1928 and 1929. Samples were obtained on the surface, and at depths of 700 and 1500 meters. The original publication identified the stoichiometric N : P ratio of 20:1, offering a light on a possible balance between these components in the ocean. In 1958, the same author (5) based on new published data recognized that a new C: N: P ratio of 106:16:1 was obtained and these are the numbers often referenced in our hobby.

A more recent and larger study (6) was made with extensive data collection (5336 distinct oceanic points). It showed a significant variation in ratios among different sites and revealed a more accurate global average for this relationship: 163:22:1. There was found a significant variation of rations between different sites.

The marine aquarium community has been using information from the original study to keep a healthier environment within the tanks. However, applicability of the original study values is very questionable since it was carried out in ocean waters.

The new interpretations of the N : P ratio

Every day more and more nitrogen-fixing organisms are studied and different N : P gradients have been identified in the nature and tested in laboratory (7). Different species benefit differently from various N : P ratios. Mathematical models have been developed to predict the prevalence of microorganisms where limiting factors are nitrogen, phosphorus or both (8).

A large number of studies include analysis of the carbon component of this equation. In order to simplify our focus, I will report more frequently the data specifically on the N : P ratio. These are the most available and practical parameters to the marine hobbyist (we usually use nitrates and phosphate tests, which are quite representative of the N: P ratio in the water column).

Could a ratio of nutrients really promote or limit the prevalence of different microorganisms in marine aquariums? Apparently yes, but it is not as simple as we previously thought.

Let's look at the biochemical basis for the different demand and composition of N : P (8). The largest pool of N is present in proteins and nucleic acids. It is also present in chlorophylls a, b, c and amino acids, and appears in diatoms chitin. In contrast, nucleic acids and phospholipids are the largest pool of P and it is less present in proteins. The main macromolecule that makes up for the cellular content in phosphate is the RNA.

But it is even a little more complex than that. Cyanobacteria have a high N: P cell ratio (> 25) comparing to most other eukaryotic microorganisms due to their significantly bulky light uptake apparatus (9). In contrast, other genera of eukaryotic phytoplankton such as green algae, diatoms and dinoflagellates have a higher content of phosphate. Evaluating just the cellular content of cyanobacteria, a high demand for nitrogen would be expected, but studies have shown exactly the opposite. Through repeated observation, it was hypothesized that cyanobacteria could supplement N deficiency with diazotrophic N2 fixation capacity (10). This N2 fixation capability also offers a better explanation for the competitive advantage of cyanobacteria over other microorganisms in nitrogen-deprived environments.

Relationships between N: P ratios and cyanobacteria

The unbalanced proliferation of cyanobacteria in estuarine and marine waters have been related to environments rich in nutrients, but lacking the N fraction of this equation. Smith has already verified in his studies that the N : P ratio below 29 favored the proliferation of cyanobacteria, which were more efficient in fixing N (11, 12).

Cyanobacteria are ubiquitous in marine aquariums, but their excessive proliferation is considered very problematic. Usually, some species are more prevalent in aquariums such as Oscillatoria , Lyngbya and Phormidium (3, 13, 14). Like other marine planktonic microorganisms, after an accelerated growth, cyanobacteria also develop a competitive advantage through secretion of allelopathic substances. These substances can inhibit the growth of other algae and cyanobacteria (15), even evidencing antimicrobial properties. This observation may partially explain the success of cyano treatment with macrolides, such as azithromycin or erythromycin. Other drugs from this group (macrolides) have already been isolated from different cyanobacteria (16). Could their mechanism of action have any similarity to allelopathy? Although it is interesting, we have not identified specific studies to verify the veracity of this hypothesis.

The initial imbalance that leads to accelerated cyano growth seems to be influenced by the N: P ratio. Ahlgren tested this hypothesis in closed environments, which we could call small aquariums (0.5L glass tubes). The researcher evaluated the proliferation of Oscillatoria agardhii in environments with limited nitrogen or phosphorus (17). He observed that in the studied species phosphorus depletion was a greater growth limit factor than nitrogen, evidencing a competitive advantage in nitrogen deprived environments. Levich (18) also studied the proliferation of cyanobacteria in detriment of other microorganisms with various N : P ratios and found very interesting balances: above 20 : 1 green algae was favored; on the other hand, cyano grew more rapidly in ratios below 5 : 1.

Implications of N : P ratios in carbon dosing

Carbon dosing is a widely used technique by marine aquarists for nutrient export and nitrate and phosphate reduction. Several carbon sources have already been tested such as sugar, vodka and vinegar. Principles of carbon dosing also seem to be explained with C : N : P ratio knowledge. Addition of carbon provides the limiting growth factor for the aquarium's bacterial population. Through this incorporation, bacteria also consume nitrate (in greater proportion) and phosphate, being later exported by the skimmer.

We also identified some studies (19) that investigated the C : N : P in these bacteria and found a ratio of 50 : 10 : 1. Exponential growth of marine bacteria in vitro was achieved when the ratio reached 32 : 6.4 : 1 in nitrogen rich and 45 : 7.4 : 1 in nitrogen poor environments.

In other words, we could expect in aquariums that the maximum export efficiency would theoretically occur in a ratio of 7 : 1 (N : P) and the expected theoretical result of consumption would occur in a ratio of 10 : 1 (N : P). This proportion was not the same in every single study, but it is closer to reality than the original Redfield (20).

Once nitrogen or phosphorus is eliminated, normally the increase in carbon supply will not remove the other residual element. Sometimes, over-dosing may stimulate the development of cyanobacteria, which can be well understood by the mechanism already mentioned: after removing the nitrogen source, cyanobacteria and others capable of fixing gaseous nitrogen (N2) could be stimulated.

Final considerations

We know that marine aquariums are closed environments with very diverse micro and macro fauna, and interpretation of this closed environment through studies carried out in nature is extremely complex. Alfred Redfield's initial studies were conducted in open waters, far away from coral reefs, so we discourage that the original Redfield ratio be taken as a rule for marine hobbysts. However, we identified the importance of his initial studies of C: N: P relationships, which were followed by the identification of new ratios in different environments.

However, many studies have demonstrated that different species usually preponderate under specific conditions. So we can check that the predominance of certain species with accelerated growth in marine aquariums seems to be influenced by the C : N : P ratio.

Higher N: P ratios (above 20 : 1) seem to favor green algae, while lower values (below 5 : 1) favor the growth of cyanobacteria. In situations where there is a critical limit in nutrients supply (a large reduction of both N and P), this interpretation seems to have less predictive value.

We must emphasize the limitations of these information and implications. The well-known imprecision of the tests that we usually use in the hobby demands that critical judgment should be used above all. Redfield did not predict with his studies events that occur in aquariums, neither it was his intention, but other studies already published seem to increasingly offer data that can help us manage marine aquariums. We believe that dissemination of this data may provide new horizons on nitrogen, phosphorus and carbon dynamics in aquariums.

Bibliography

1. Dellbeek JC, Sprung J. The Reef Aquarium: A Comprehensive Guide to the Identification and Care of Tropical Marine Invertebrates. 3: Two Little Fishies, Inc.; 1994. p. 274-5.

2. Basso JC. In: Aquaribasso, editor. O Aquário de Recife de Corais. 2017. p. 45.

3. Knop D. Algues en aquarium. Les guides Zebras. 2010:59-63.

4. Redfield AC. On the proportions of organic derivatives in sea water and their relation to the composition of plankton. James Johnstone Memorial. 1934;176:176-92.

5. Redfield AC. The Biological Control of Chemical Factors in the Environment. American Scientist. 1958;46(3):230A-21.

6. Martiny AC, Vrugt JA, Lomas MW. Concentrations and ratios of particulate organic carbon, nitrogen, and phosphorus in the global ocean. Scientific Data. 2014;1(1):140048.

7. Gruber N, Deutsch CA. Redfield's evolving legacy. Nature Geoscience. 2014;7(12):853-5.

8. Geider R, La Roche J. Redfield revisited: variability of C : N : P in marine microalgae and its biochemical basis. European Journal of Phycology. 2002;37(1):1-17.

9. M B, M S. Factors affecting the growth of cyanobacteria with special emphasis on the Sacramento-San Joaquin Delta.: Southern California Coastal Water Research Project; 2015.

10. Parrish J. The Role of Nitrogen and Phosphorus in the Growth, Toxicity, and Distribution of the Toxic Cyanobacteria, Microcystis aeruginosa. Master's Projects and Capstones: University of San Francisco; 2014.

11. Smith VH. Low Nitrogen to Phosphorus Ratios Favor Dominance by Blue-Green Algae in Lake Phytoplankton. Science. 1983;221(4611):669-71.

12. Smith VH. Nitrogen, phosphorus, and nitrogen fixation in lacustrine and estuarine ecosystems. Limnology and Oceanography. 1990;35(8):1852-9.

13. Sprung J. Algae: A Problem Solver Guide: Two Little Fishies; 2001.

14. Nienaber MA, Steinitz-Kannan M. A guide to cyanobacteria: identification and impact: Univeristy Press of Kentucky; 2018.

15. Chauhan VS, Marwah JB, Bagchi SN. Effect of an antibiotic from Oscillatoria sp. on phytoplankters, higher plants and mice. New Phytologist. 1992;120(2):251-7.

16. Wang M, Zhang J, He S, Yan X. A Review Study on Macrolides Isolated from Cyanobacteria. Mar Drugs. 2017;15(5):126.

17. Ahlgren G. Growth of Oscillatoria agardhii in Chemostat Culture: 1. Nitrogen and Phosphorus Requirements. Oikos. 1977;29:209.

18. Levich AP. The role of nitrogen-phosphorus ratio in selecting for dominance of phytoplankton by cyanobacteria or green algae and its application to reservoir management. Journal of Aquatic Ecosystem Health. 1996;5(1):55-61.

19. Vrede K, Heldal M, Norland S, Bratbak G. Elemental Composition (C, N, P) and Cell Volume of Exponentially Growing and Nutrient-Limited Bacterioplankton. Applied and Environmental Microbiology. 2002;68(6):2965-71.

20. Chrzanowski TH, Kyle M. Ratios of carbon, nitrogen and phosphorus in Pseudomonas fluorescens as a model for bacterial element ratios and nutrient regeneration. Aquatic Microbial Ecology - AQUAT MICROB ECOL. 1996;10:115-22.

Thank you for the big post. I want to recognize your effort to synthesize the “big picture” on this hot topic. I appreciate the title.

“What are we doing wrong” could be answered simply with the statement that the Redfield ratio application to maintaining artificial marine environments is an incompletely developed idea driven by our desire for a simple approach for maintaining our reef systems. “Just keep nitrate and phosphate levels at X in a ratio of A/B for a healthy, trouble free aquarium”. Don’t we wish! In a more thoughtful reply to the question, here are some possible ways we went wrong with the Redfield ratio in maintaining artificial marine systems: confused effect with cause, confused benthic with pelagic and chemistry focused and microbiologically blind.

Confused cause-effect. Redfield’s 1934 publication is one the big ideas behind ecological stoichiometry, the study of elements in biomass and the environment in an attempt to characterize and understand how ecological systems function and whether they are in a stable state. The important notion here is that to study a system, you need two ratios to characterize the system, the element ratio in the environment and the element ratio of the biomass in the environment. A elementally balanced system would have the ratio of elements the same in both the biomass and the environment. This is what Redfield observed in 1934 for his ocean samples. Whether the system is elementally balanced or imbalanced is the effect of how the system works. Adding elements to the environment might mathematically balance the ratios, but it does not change the system‘s the performance. The system is balanced or unbalanced for many other possible reasons. The Redfield ratio per se may not be useful for aquarium keepers, but the perspectives gained through ecological stoichiometry studies might. One important take away from this discussion is that you need to obtain two ratios , one for the biomass and one for the environment to describe your aquarium. Attempting to manage your aquarium knowing only the nitratehosphate ratio in the water is like trying to ride a bicycle with one wheel.

Confused benthic with pelagic. Where in our systems do we find nuisance organism growth? On surfaces and in sand beds. How do we attempt to define the cause? By measuring something in the water. Why do we think there is a connection? I would guess most aquarium keepers think this way, even the experts. And yet the success at controlling nuisance growth by tweaks to nutrient levels In the water is erratic at best, maybe close to 50:50. A possible explanation is that most benthic organisms are obtaining most if not all their required nutrients right where they are growing and very little from the water. We might have wondered why nuisance growth is occurring in isolated patches if they are getting nutrients from the water. You might also have wondered why all the quoted scientific references on nuisance growth are studies of pelagic nuisance organisms, the kind we rarely if ever have problems with? I provide this perspective and provocative (annoying?) questions to introduce another possible reason why the Redfield ratio does not seem to be a useful number. Our systems are a combination of benthic and pelagic environments, a combination of metabolisms and biomass that may not be reflected in the Redfield ratio. Adjusting the water NO3O4 ratio without reference to the benthic N ratio could be counterproductive. Without understanding the big picture behind the water N ratio, adjustments are a shot in the dark.

Chemistry focused, microbiologically blind. We tend to view the world in terms of the tools we use. If we can only measure nitrate and phosphate, we tend to explain nuisance growth by these levels. We tend to see patterns where there are none. How does nitrate in the water explain an isolated patch of cyanobacteria, diatoms or dinoflagellates? The answer is not dissolved organics. And why do we assume we have a cyanobacteria, a diatom or A dinoflagellate problem instead of a local ecological problem started by bacteria growth which made the isolated area friendly to cyanobacteria, diatoms or dinoflagellates? For one thing we can measure a nitrate concentration but not a bacteria colony. And even though the nitrate level is a poor predictor of nuisance organism growth, it is all we have. And here is another possible reason the Redfield ratio might not be very useful. The N ratio in the water is irrelevant.

I don’t known whether any part of this perspective is useful. Maybe it will fun to kick around the ideas.

 

[Lasse]

And why do we assume we have a cyanobacteria, a diatom or A dinoflagellate problem instead of a local ecological problem started by bacteria growth which made the isolated area friendly to cyanobacteria, diatoms or dinoflagellates? For one thing we can measure a nitrate concentration but not a bacteria colony.

[/QUOTE]
May I use a old quote?

Eppur si muove

In this case - tweaking the NO3 and PO4 concentrations in the water column is still the most effective way to handle all of these three photosynthetic organisms when they form monocultures.

Sincerely Lasse

 

[Reef and Dive]

Yeah, great answers this discussion gets exciting.

As @Dan_P pointed out, many times nutrients available in microenvironment sometimes play an important role: as an example we often find cyano limited to a single rock, wich might lead to a specific niche rich in bound phosphate.

But I also agree with @Lasse that the easiest way to manage in most times is just with a deeper comprehension of those nutrients in the water.

As pointed in my first post, I searched many newer studies on that balance, since the original Redfield’s study is quite full of incorrections due to the moment, limitations and even objectives at that time. It just pointed us some directions, that have been much better studied to this date.

 

[Dan_P]

May I use a old quote?

In this case - tweaking the NO3 and PO4 concentrations in the water column is still the most effective way to handle all of these three photosynthetic organisms when they form monocultures.

Sincerely Lasse
[/QUOTE]
Thanks for your reply. I thought my “tweaking“ comment might entice you to reply

On this topic, I remain a skeptic. Anecdotal data and uncontrolled experiments are just hard for me to accept as evidence. Also, these organism growths are unlikely to be “monocultures”. The monoculture notion is an assumption, possibly supported by casual microscopy observations, but still an assumption.

Respectfully,

Dan

 

[Reef and Dive]

May I use a old quote?

In this case - tweaking the NO3 and PO4 concentrations in the water column is still the most effective way to handle all of these three photosynthetic organisms when they form monocultures.

Sincerely Lasse

Thanks for your reply. I thought my “tweaking“ comment might entice you to reply

On this topic, I remain a skeptic. Anecdotal data and uncontrolled experiments are just hard for me to accept as evidence. Also, these organism growths are unlikely to be “monocultures”. The monoculture notion is an assumption, possibly supported by casual microscopy observations, but still an assumption.

Respectfully,

Dan
[/QUOTE]

Yes Dan, but when you have some time check the bibliography I provided... my objective was to search for better evidence than anecdotal data and uncontrolled experiments to better understand this... Found some nice studies.

I’ve read those articles entirelly and with detail to write this. I can provide their PDF for anyone interested.

 

[Dan_P]

Thanks for your reply. I thought my “tweaking“ comment might entice you to reply

On this topic, I remain a skeptic. Anecdotal data and uncontrolled experiments are just hard for me to accept as evidence. Also, these organism growths are unlikely to be “monocultures”. The monoculture notion is an assumption, possibly supported by casual microscopy observations, but still an assumption.

Respectfully,

Dan

Yes Dan, but when you have some time check the bibliography I provided... my objective was to search for better evidence than anecdotal data and uncontrolled experiments to better understand this... Found some nice studies.
[/QUOTE]

The bibliography is a nice collection, definitely. We are indebted to to you. We should make it clear that It represents a tiny fraction of the science being done on microorganisms of interest to us.

When you find controlled studies of aquariums, then real progress will be made. Studies of isolated pelagic organisms, even if they are freshwater organisms, provide us with Some useful information about that individual species and maybe the genus. Studies of the actual nuisance marine organisms in aquaria-like settings would be even more useful. Studying the consortium of organisms involved in nuisance organism growth is what will likely sort out the causes of their growth.

Dan

 

[Lasse]

Anecdotal data and uncontrolled experiments are just hard for me to accept as evidence.

Understand that - but you will maybe also understand why I´m sceptical to statements that´s not even is based on anecdotal data - just based on a statement that x and y may not act that way - they must act in this way.

Sincerely Lasse

 

[Dan_P]

Understand that - but you will maybe also understand why I´m sceptical to statements that´s not even is based on anecdotal data - just based on a statement that x and y may not act that way - they must act in this way.

Sincerely Lasse

Of course! I totally understand where you are coming from.

What sort of experiment could we set up to test the notion that NO3 and PO4 level adjustments actually alter microorganism populations?

How could we possibly create 6 identical systems with nuisance organism growth, 3 would receive no intervention, 3 would receive our best estimate for the right level of NO3 and PO4 adjustment? Basically, how do we reproducibly create a cyanobacteria, diatom or dinoflagellate bloom in six small containers at the same time with roughly the same size bloom, maybe in 5-20 liters of water? Or would it be smarter to create a large bloom and divide it in 6 equal parts for the study?

Dan

 

[Reef and Dive]

Of course! I totally understand where you are coming from.

What sort of experiment could we set up to test the notion that NO3 and PO4 level adjustments actually alter microorganism populations?

How could we possibly create 6 identical systems with nuisance organism growth, 3 would receive no intervention, 3 would receive our best estimate for the right level of NO3 and PO4 adjustment? Basically, how do we reproducibly create a cyanobacteria, diatom or dinoflagellate bloom in six small containers at the same time with roughly the same size bloom, maybe in 5-20 liters of water? Or would it be smarter to create a large bloom and divide it in 6 equal parts for the study?

Dan

Dan I do not believe researchers have intention to publish studies to convince us hobbiysts of anything. Nor do I believe that the absence of studies that do not meet out expectations should move us away from science...

Those files attached are some examples among other studies that showed evidence favouring one or another group of organisms.

This was observed in nature and in vitro, and they actually cultivated some cyanos like Oscillatoria to research the best conditions of growth for it.

For diatoms and dinos most studies put them together in terms of nutrients (but it is well known the role of silica to support the first group).

 

[Lasse]

How could we possibly create 6 identical systems with nuisance organism growth, 3 would receive no intervention, 3 would receive our best estimate for the right level of NO3 and PO4 adjustment? Basically, how do we reproducibly create a cyanobacteria, diatom or dinoflagellate bloom in six small containers at the same time with roughly the same size bloom, maybe in 5-20 liters of water? Or would it be smarter to create a large bloom and divide it in 6 equal parts for the study?

It is impossible - and you know it. It is like saying that Colombus should have taken an airplane around the world in order to find another way to India.

But let it us turn the question upside down. All system is different - every system is its own ecosystem with different microbial communities - in the US, in the UK in Brazil and in Sweden.

Despite this, we know that in at least 80 - 90% of cyanobacteria and dinoflagellar outbreaks have been reported at low or unbalanced concentrations of PO4 and different form of inorganic nitrogen. In addition, for cyanobacteria, the NO3 concentration seems to be critical. Low or no levels (and sometimes wrong ratio) of these substances in the water column have been shown to be the trigger over and over again. However - nearly all aquarium books refer to this problems as high nutrients problems - not because of evidences, scientifically investigations or thousand of of observations - but because of the fact that photosynthesizing organism in water needs nutrients in the water column - otherwise they will not grow. I´m with you when you say that these organisms have different ways of achieve the P and N they need - but for me it is very strong incidental evidence´s that low/zero or unbalanced ratios of these two nutrients is the trigger for creating different forms of monocultures existing of one or two species/genus that dominate the ecosystem. They can dominate because the environment that favour other competitors is gone and lost. They can dominate because they have other way of getting what they need - if the easy achieved sources not exist they can put in extra energy in order to survive and the domination and huge biomass will be the tool for further success if not the environment will change. Note - I´m not saying that the rise of nutrient in the water column (or changes of the ratios) will automatically defeat the monoculture but it is a tool to not get it back when the fight is over. Rising the nutrient during an outbreak of these organisms is not a quick fix - but lowering the nutrients (or change the ratio in the wrong way) is surly a quick fix in order to get an outbreak IMO.

I have not mentioned diatoms - but for me is rather obvious that a diatom bloom in our aquaria is not triggered of visible Si in the water column - the use of ICP testings worldwide have shown that the normal Si levels in out aquarium is over 100 µg/L - even in well function aquariums without diatom blooms. However - there is a lot of investigations showing that at least some diatoms are specialist in using very low concentrations of inorganic P in the water column and I see diatoms blooms in our aquarium as a sign of low availability of PO4 not as a sign of Si in the water column.

But today - it seems that we instead of knowledge and understanding of complicated processes need something easy to put the blame on - however - this is nothing new - let us - as usually - say it with a song (and @Paul B get his supermodel at the same time)



Sincerely Lasse