Redfield ratio as it pertains to the reef or your reef is stupid and pointless

[Lasse]

It doubled mass on its next cycle. It also harbored a slime bacterial colony downstream of the scrubber, presumably fueled by algae exudates.

That´s known that both microalgae and macroalgae can excrete DOC - mostly in form of sugar (or other carbohydrates) that can feed heterophic bacteria and they are normally organic carbon limited in a normal aquarium. In our different systems - its necessary to distinguish between inorganic and organic carbon because they are carbon sources for different trophic levels. You can say the form of carbon that´s waste fro one trophic level is the needed for the other level. and the other way around.

Sincerely Lasse

 

[Randy Holmes-Farley]

Limited phosphorus availability is the Achilles heel of tropical reef corals in a warming ocean - Scientific Reports

During the 20th century, seawater temperatures have significantly increased, leading to profound alterations in biogeochemical cycles and ecosystem processes. Elevated temperatures have also caused massive bleaching (symbiont/pigment loss) of autotrophic symbioses, such as in...

www.nature.com

Redfield ratio maybe be dead in reefing but - IMO - N/P ratio in the water can have an importance

Sincerely Lasse

Hi Lasse,

Can you explain how that article says the N : P ratio is important, rather than each of N and P is needed in an optimal range, and that optimal range might change with changing conditions such as temperature increases?

For the ratio to be the important, it would suggest that critical value is the ratio, rather than the absolute values, and that changing the absolute values with the same ratio is not important. I did not see that in the paper.

 

[Mickeyt1reef]

I just try to keep nitrate higher than phosphate. Done

 

[flampton]

The nutrient in the water column is mostly interesting from photosynthetic organism point of view - ie autotrophic organisms. They use inorganic N and P. And of cause inorganic C. To talk about a carbon limitation in this aspect is not true. As I said before - saltwater with alkalinity around 2.5 mekv is in no way limited according to inorganic carbon. All phototrophic organisms in saltwater I´m aware off have the possibility to use (or convert) mainly HCO3 into needed CO3

If you look at heterotrophic organisms - its true - an aquarium is limited in organic carbon - especially of the form we use to call DOC (Dissolved Organic Carbon). But that has nothing to do with the inorganic balance of N,P and C for the phototropic organisms.

Before your fingers get overheated in attempt to tell me that I´m an idiot that do not understand that bacteria will - in especially in the presence of a "fast" organic carbon sources (DOC) - convert the organic carbon into inorganic carbon (namly CO2). I can tell you that I understand that - but I also understand that adding CO2 will not affected the storage level of inorganic carbon (the major part of the alkalinity) - it will only affect the pH and hence the equilibrium between CO2 <->H2CO3 <-> HCO2 <-> CO3 - not the total stored amount. I also understand that CO2 is a gas and will follow the equilibrium laws in an air/water interface and disappear from the element we call saltwater.

I have never talk about a ideal ratio of nutrients in the water - it will be different in different situations. If you run a macro dominated tank there the N/P ratio in the organisms often can exceed 50:1 and that your ratio in the water is around 20:1 even with your influx (the concentration in the water column is the difference between production/import and internal consumption) - you do need to be an Einstein to understand that the storage of N in the water column will be depleted in time and transferred into the macros in another ratio.

The ratio (read the left over or storage pool) of inorganic N and P need to be adjusted (IMO) to the phototropic organisms demand for these nutrients. And if you chose to have 0 nutrients in the water - your daily influx of these two inorganic nutrients must have a ratio that will not create an growth limitation of your phototrophic organisms.

I will - with the stubbornness of a fool - still say that according at least P - measurements of the left over or with other words - the storage pool in the water column - with help of PO4 measurements is important. If the concentration rise - internal production/equilibrium/import is higher than internal consumption/equilibrium/export - if it decline - If the concentration decline - internal production/equilibrium/import is lower than internal consumption/equilibrium/export, With inorganic N its more complicated - only measurement of NO3 can give a false impression of the inorganic N ratio but an indication if the storage pool of inorganic N. I use Triton N-DOC analyses in order to check my whole storage pool of inorganic and organic N (in the water column) but the NO3 concentration as a tool in order to get a snapshot now a when where the system is going.

Sincerely Lasse

In actuality you still are running a carbon limitation. To access the CO2 the phototrophs require light. The aquarist controls this by manipulating intensity spectrum duration. As well as those who run ATS or algal refugium control the production of organic carbon to a separate compartment.

 

[Lasse]

IMO - the basic in this article and some other articles are that if N availability is to high compared with the availability of P - the corals will be P limited and this compared with thermal stress will cause bleaching. During normal condition - it is N that is the limited factor but the change of limited factor compared with thermal stress will bleach natural coral reefs.

However this seems mostly valid in PO4 concentrations below 0.03 mg/L - if there is an absolute concentration above 0.03-0.04 mg/L PO4 itsdo not matter with the ratios - I think I got this information from this article below that talk about bleaching without thermal stress

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with din…

www.sciencedirect.com

The abstract from this article

Abstract​

Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with dinoflagellates (Symbiodinium sp.). We argue, however, that the direct negative effects on the symbiosis are not necessarily caused by the nutrient enrichment itself but by the phosphorus starvation of the algal symbionts that can be caused by skewed nitrogen (N) to phosphorus (P) ratios. We exposed corals to imbalanced N ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals. In contrast, the corals tolerated an undersupply with nitrogen at high phosphate concentrations without negative effects on symbiont photosynthesis, suggesting a better adaptation to nitrogen limitation. Transmission electron microscopy analysis revealed that the signatures of ultrastructural biomarkers represent versatile tools for the classification of nutrient stress in symbiotic algae. Notably, high N ratios in the water were clearly identified by the accumulation of uric acid crystals.

Myself have set a target level of between 0.04 - 0.1 in PO4 - just because I want to be over the concentrations that can cause inorganic P starvation if the inorganic N concentration is to high. Maybe the right answer is (as it normal is) - It depends on

Sincerely Lasse

 

[Lasse]

In actuality you still are running a carbon limitation. To access the CO2 the phototrophs require light. The aquarist controls this by manipulating intensity spectrum duration. As well as those who run ATS or algal refugium control the production of organic carbon to a separate compartment.

Now it is a mix of bananas, apples, pears and oranges again. A phototrophic organism in normal saltwater can be limited of whatever you name - but with one exception - inorganic C. With an alkalinity of around 2.5 mekv - inorganic C can never be a limited factor for growth and health of any phototrophic organism in saltwater or high alkalinity freshwater system. Light can be limited, inorganic P can be limited, inorganic N can be limited, inorganic K can be limited, iron can be limited and whatever can be limited - but never, ever inorganic carbon if a certain alkalinity exist. In low pH natural freshwater system like the Amazonas - inorganic C can be limited but not in normal saltwater - never, ever. If alkalinity goes down to zero in a saltwater system it has already crashed long time before.

Sincerely Lasse

 

[Randy Holmes-Farley]

IMO - the basic in this article and some other articles are that if N availability is to high compared with the availability of P - the corals will be P limited and this compared with thermal stress will cause bleaching. During normal condition - it is N that is the limited factor but the change of limited factor compared with thermal stress will bleach natural coral reefs.

I don't disagree with any of that experimental observation, and I think the data in this paper show that ratios are NOT the important factor: it is only the absolute values that matter.

They say
"Corals exposed to the imbalanced, HN/LP conditions, displayed a smaller polyp size and a bleached appearance that closely resembled the phenotype observed in low nutrient water (LN/LP) "

and

"Our results suggest that symbiotic corals can tolerate an undersupply with nitrogen much better than an undersupply with phosphorus. "

Their data and statement basically says that low P is bad, not that it was the ratio that mattered. When P is low, it doesn't matter what the ratio is, it is bad.

IMO, this paper clarifies that the ratio is NOT the important factor.

 

[Randy Holmes-Farley]

With an alkalinity of around 2.5 mekv - inorganic C can never be a limited factor for growth and health of any phototrophic organism in saltwater or high alkalinity freshwater system. Light can be limited, inorganic P can be limited, inorganic N can be limited, inorganic K can be limited, iron can be limited and whatever can be limited - but never, ever inorganic carbon if a certain alkalinity exist. In low pH natural freshwater system like the Amazonas - inorganic C can be limited but not in normal saltwater - never, ever. If alkalinity goes down to zero in a saltwater system it has already crashed long time before.

Sincerely Lasse

Never?

While many macroalgae use bicarbonate for CO2 (table 1 in my article below), some apparently do not do so very effectively, and photosynthesis drops as CO2 drops :

Photosynthesis and the Reef Aquarium, Part I: Carbon Sources by Randy Holmes-Farley - Reefkeeping.com

For example, the red marine macroalgae GELIDIUM SESQUIPEDALE :

https://onlinelibrary.wiley.com/doi/abs/10.1046/j.1529-8817.1998.340925.x

"Photosynthesis by G. sesquipedale was enhanced when CO2 concentration was increased in the medium by a decrease in pH. On the other hand, an increase in pH from 8.1 to 8.7 produced a significant reduction of the O2 evolution rates indicating that G. sesquipedale has a very low capacity to use HCO3−. "

 

[Lasse]

Never?

I´m old enough and should have learned to never say never according to biological systems My bad

Sincerely Lasse

 

[flampton]

Now it is a mix of bananas, apples, pears and oranges again. A phototrophic organism in normal saltwater can be limited of whatever you name - but with one exception - inorganic C. With an alkalinity of around 2.5 mekv - inorganic C can never be a limited factor for growth and health of any phototrophic organism in saltwater or high alkalinity freshwater system. Light can be limited, inorganic P can be limited, inorganic N can be limited, inorganic K can be limited, iron can be limited and whatever can be limited - but never, ever inorganic carbon if a certain alkalinity exist. In low pH natural freshwater system like the Amazonas - inorganic C can be limited but not in normal saltwater - never, ever. If alkalinity goes down to zero in a saltwater system it has already crashed long time before.

Sincerely Lasse

That's funny considering when the lights are out the phototrophs are actively expelling the CO2 they produce.

Basically your argument boils down to this...
A human floating in a pool is not water limited.

 

[Lasse]

A human floating in a pool is not water limited.

Exactly - it is the opposite to say A human floating in a pool is alcohol limited

That's funny considering when the lights are out the phototrophs are actively expelling the CO2 they produce

Exactly and if not all have been aerated out to the air during the dark period - they can use it again when the light arrive in the morning - the opposite to limited

I think you got it now

Sincerely Lasse

 

[Lasse]

I don't disagree with any of that experimental observation, and I think the data in this paper show that ratios are NOT the important factor: it is only the absolute values that matter.

They say
"Corals exposed to the imbalanced, HN/LP conditions, displayed a smaller polyp size and a bleached appearance that closely resembled the phenotype observed in low nutrient water (LN/LP) "

and

"Our results suggest that symbiotic corals can tolerate an undersupply with nitrogen much better than an undersupply with phosphorus. "

Their data and statement basically says that low P is bad, not that it was the ratio that mattered. When P is low, it doesn't matter what the ratio is, it is bad.

IMO, this paper clarifies that the ratio is NOT the important factor.

They also say somewhere that the P concentrations that create bleaching events in their experiments is rather normal reported concentrations in natural water without bleaching (around 0,01- 0,03 mg/L PO4 if I have done the conversion from µM to mg/L the right way (they talk about 0.18 µM - 0.3 µM phosphate). But they also stated that the normal systems was nitrogen limited. It means that if the ration between inorganic N and P rise - normal P values could become a limited factor - with other words - at below special threshold (they talk about 0.3 µM) - the ratio could be important - but not over a certain threshold of PO4

I´ll think that if you of some reason want to run a near zero PO4 system (some people fascinated of coloured sticks love to do that) you need to have some control over the N/P ratio - not let it rise to much. But for me - its enough to not get lower than the threshold in this article - if I do not - the ratio have not so much importance. But I think that @Hans-Werner can explain this better than me - I hope he take this bait

Sincerely Lasse

 

[Nano sapiens]

I don't disagree with any of that experimental observation, and I think the data in this paper show that ratios are NOT the important factor: it is only the absolute values that matter.

They say
"Corals exposed to the imbalanced, HN/LP conditions, displayed a smaller polyp size and a bleached appearance that closely resembled the phenotype observed in low nutrient water (LN/LP) "

and

"Our results suggest that symbiotic corals can tolerate an undersupply with nitrogen much better than an undersupply with phosphorus. "

Their data and statement basically says that low P is bad, not that it was the ratio that mattered. When P is low, it doesn't matter what the ratio is, it is bad.

IMO, this paper clarifies that the ratio is NOT the important factor.

What I found most interesting is that the article mentions a difference between LN/LP and HN/LP:

"Since corals from the HN/LP conditions were supplied with excess nitrogen, the nutrient limitation phenotype of corals and symbionts can be clearly attributed to the undersupply with phosphate. Importantly, under both, nutrient replete and low nutrient conditions, the photosynthetic efficiency measured as Fv/Fm was in the healthy range (> 0.5). In contrast, Fv/Fm was strongly reduced in the imbalanced HN/LP treatment, indicative of failing photosynthesis due to phosphate starvation (Wiedenmann et al., 2013, D'Angelo and Wiedenmann, 2014). At ultrastructural level, the phosphate starvation phenotype resulting from nitrogen enrichment in combination with low phosphate supply can be clearly distinguished from the low-nutrient phenotype by the pronounced accumulation of uric acid crystals. This finding is in line with previous studies that observed comparable deposits in zooxanthellae in response to nitrate enrichment, forming a transitory storage of assimilated nitrogen (Clode et al., 2009, Kopp et al., 2013). Finally, the phosphate-starved zooxanthellae lack the intriguing fragmentation pattern of the accumulation body, characteristic of strongly nutrient-limited zooxanthellae (Rosset et al., 2015)."

...and

"The present study clearly shows that phosphate deficiency, alone or in combination with a low supply of nitrate, results in a severe disturbance of the symbiotic partnership as indicated by the loss of coral tissue and zooxanthellae. Phosphate starvation of zooxanthellae induced by nitrogen enrichment and resulting high N ratios has previously been shown to disturb the photosynthetic capacity of zooxanthellae and increase the vulnerability of corals to light- and heat stress-mediated bleaching (Wiedenmann et al., 2013)."

This study indicates that there is clearly a difference in effect between LN/LP and HN/LP, as evidenced by uric acid formation and disturbance of the photosynthetic capacity in HN/LP. In my mind, this indicates that there is a point where increasing N starts to become detrimental as P remains limited and this effect is more detrimental than a LN/LP condition.

Would this not indicate that a certain ratio is involved (not explored in this study)where the 'more detrimental effects' mentioned in my paragraph above begin to be observed, when P is kept at a consistent low concentration?

 

[Randy Holmes-Farley]

Just so that everyone can interpret this published experiment in relation to reef tanks sorts of recommended values, here's the conversion of their numbers:

high nitrogen (HN) = ~ 38 μM NO3− --> 2,356 ug/L ~ 2.4 ppm nitrate
low nitrogen (LN) = ~ 0.06 μM NO3− --> 3.7 ug/l ~ 0.004 ppm nitrate

high phosphorus (HP) = ~3.6 μM PO4− --> 342 ug/L ~0.3 ppm phosphate
low phosphorus (LP) = ~0.18 μM PO4− --> 17 ug/L ~0.017 ppm

FWIW, the LN situation is well below what most reefers empirically find to be optimal.

 

[Garf]

I particularly like this bit

Effects of P deficiency can be expected to become worse if supply from other sources such as particulate food or internal reserves, is low.

 

[Randy Holmes-Farley]

Would this not indicate that a certain ratio is involved (not explored in this study)where the 'more detrimental effects' mentioned in my paragraph above begin to be observed, when P is kept at a consistent low concentration?

It would be interesting (necessary?), IMO, to support the idea that ratios are what is important, to test different absolute concentrations with the same ratio of N : P. I've never seen such a study.

This experiment is complicated by the fact that these corals are not getting any particulate foods, which isn't likely true in a reef aquarium or in thw wild.