Low nitrates/phosphates cause algae to grow? Whattt?

[Azedenkae]

So I had always thought that algae and stuff are often associated with very low nitrate/phosphate readings simply because they soak up all the nutrients, hence the low readings.

Yet I keep on reading recently that low nitrates/phosphates is actually the cause of some variants of algae to overgrow, rather than vice versa.

So what is the explanation for this? Why is there a belief that low nutrients (well, nitrates/phosphates) actually causes algae to grow?

I don't know enough about algae to really know if I might be missing something very straightforward here.

 

[NeonRabbit221B]

Dinos can take off if nutrients bottom out. Not sure about other forms of algae

 

[EuphylliaAddict]

It's all a balance. The ranges everyone says is just an ideal range, I would refer to the Redfield ratio.

 

[Randy Holmes-Farley]

In the general case, I do not believe there are ANY examples of an algae that grows better at lower nutrients if it is in isolation.

What can happen, is that at low nutrients, the pest may outcompete something else that cannot grow as well at the lower nutrient levels. If you then raise nutrients, taht other things (say, a different type of algae) may begin to grow faster and outcompete the pest.

I actually think this is only clearly demonstrated for dinos in reef tanks, but might possibly apply to other pests as well.

FWIW, the thing they are competing for might be space, or a trace element, such as iron (which may be why water changes seem to encourage dinos).

 

[Randy Holmes-Farley]

It's all a balance. The ranges everyone says is just an ideal range, I would refer to the Redfield ratio.

IMO, there's almost no utility for the Redfield or any other ratio in reefkeeping nutrient considerations.

Each nutrient should be kept in an optimal range for the organisms present, and just because one nutrient might fall outside that range is not a reason to think it desirable for the others to do so.

At the extremes, ratios are clearly utterly useless.

Suppose that you think that 5 ppm nitrate and 0.02 ppm phosphate is a desirable set of parameters.

Does that in ANY conceivable way suggest that 0.005 ppm nitrate and 0.00002 ppm phosphate is equally desirable, despite having the same ratio

Of course not. It's ratios run amok.

 

[Dan_P]

So I had always thought that algae and stuff are often associated with very low nitrate/phosphate readings simply because they soak up all the nutrients, hence the low readings.

Yet I keep on reading recently that low nitrates/phosphates is actually the cause of some variants of algae to overgrow, rather than vice versa.

So what is the explanation for this? Why is there a belief that low nutrients (well, nitrates/phosphates) actually causes algae to grow?

I don't know enough about algae to really know if I might be missing something very straightforward here.

It is a popular idea. My opinion about it can bounce back and forth between “MMM, strangely appealing” to “this is nonsense”. Like the cold fusion idea, low nutrients causing nuisance microorganism flies in the face of what we know about how life works, which is more food more growth (I know it’s more complicated than this).

The defenders of the idea work very hard to make the case that low nutrients starve everything else but this one species that is a nuisance. It has the world to itself because the competition suddenly starved to death. What a nasty coincidence, right?

The part of me that likes the idea says, hold on doubting Thomas, there is a thing called the biofilm on all the aquarium surfaces.. The biofilm where dinoflagellates live is a complex community of interacting organisms. It might just be that for some systems or maybe most new systems, but definitely not all systems, that this biofilm can be damaged by low nitrate or phosphate, and either the nutrients released by the dying organisms or the newly available space or both is a boon to dinoflagellates.

it is all a bunch of hand waving in the end. No one has come up with data from controlled experiments to actually demonstrate the effect. I think @taricha might have made a decent attempt to demonstrate the “low nutrients cause dinoflagellate growth”. Let’s see what he’s got

 

[Randy Holmes-Farley]

The part of me that likes the idea says, hold on doubting Thomas, there is a thing called the biofilm on all the aquarium surfaces.. The biofilm where dinoflagellates live is a complex community of interacting organisms. It might just be that for some systems or maybe most new systems, but definitely not all systems, that this biofilm can be damaged by low nitrate or phosphate, and either the nutrients released by the dying organisms or the newly available space or both is a boon to dinoflagellates.

I think that is quite plausible for dinos, but may not explain the apparent effect that water changes have (boosting dinos).

 

[Dan_P]

I think that is quite plausible for dinos, but may not explain the apparent effect that water changes have (boosting dinos).

Yes, the water change is another story to think about. it is not so odd sounding, right: water change adds something to the system that stimulates growth.

Still, being the skeptic that I am, would be much happier if you could consistently show removing 10% of a system’s water and putting it right back in does not stimulate dinoflagellates.

 

[Garf]

Some algae propagate bacterial films which convert dissolved organics to inorganic forms of N and P for uptake, so these are not detectable.

 

[Azedenkae]

Thank you everyone for your replies. So far I am not convinced.

If the whole idea is simply that certain organisms can suddenly prosper because they utilize certain nutrients more so than others and can outcompete other organisms because the organisms now lack a certain specific nutrient, then sure, that is fully understandable and is exactly what would be expected. Or if certain compounds/molecules are converted to something else and we can't really measure it but that causes a sudden rapid growth/reproduction of organisms, also sure. Either way though, it is not a lack of nutrients that is causing the growth, it is still... nutrients causing the growth, whatever the nutrients may be, and that there is a growth of whatever organisms that can make best use of whatever nutrients is available.

But yeah, I think this quote from Randy best sums up my current thoughts:

I do not believe there are ANY examples of an algae that grows better at lower nutrients if it is in isolation.

If any of these algae is grown by itself in a medium that is low in the nutrients it needs to grow, then I do not think it will grow.

The only way I can see how low nutrients can cause something to grow is if that organism is a lithoautotrophic organism that can derive everything just from inorganic compounds readily available in the water. But then again, that just means one is exclusive such inorganic compounds from the definition of what 'nutrients' are. In which case... sure? But then it's a matter of definitions, rather than anything else.

But hey, like I said, I am not an expert in this field, just am yet to be convinced. Just to clarify, a lot of what everyone is saying does make sense, but for me just does not fit the definition of 'low nutrients causes growth/reproduction/etc.'

Maybe @taricha can indeed share experiences/data/etc. to say otherwise.

 

[taricha]

it is all a bunch of hand waving in the end. No one has come up with data from controlled experiments to actually demonstrate the effect. I think @taricha might have made a decent attempt to demonstrate the “low nutrients cause dinoflagellate growth”.

no controlled experiments here. Just big bags of anecdotes and reasoning from published lit.

The big dinoflagellate bloom in my system happened when I had a GHA issue, and used GFO and carbon dosing to push PO4 lower and lower. As the GHA receded and was on the verge of total disappearance, brown slime took over the sand. This and similar is the most common origin story for dino outbreaks in the hobby.
"Did x to push nutrients low to get rid of some other algae, as it works... brown slime appears."

I've taken active live microscoped ostreopsis/prorocentrum blooms from a tiny test tank at undetectable NO3, and very low PO4 and poured it into my display (after the display had shed the dino outbreak), the display had higher NO3 = 10ppm and PO4 0.10-0.15. and the dinos formed the barest bubbles and a string or two, but did not bloom. (Do I think NO3/PO4 were the most important variables here? no.)

Let's take a look at a few bits of published lit that might help...
Review of the main ecological features affecting benthic dinoflagellate blooms

Nutrient remineralisation in sediments is important and also enhanced by
warm temperatures, so release of nutrients by the sediments can provide a
continuous nutrient supply that can be instantaneously taken up by all benthic
algae and hence, nutrient concentrations remain low. All these factors may
explain why benthic dinoflagellates can bloom in warm and nutrient poor waters (Tindall & Morton, 1998; Shears & Ross, 2009; Pistocchi et al., 2011).

The f/2 medium is the most commonly used to grow marine microalgae
giving excellent results in most cases. However, there are many experiences in
which, using full strength medium to grow benthic dinoflagellates, the cells appear
distorted and they do not grow well, while those grown on a diluted medium look
much healthier (Holmes et al., 1990). This can reflect the fact that they are
adapted to grow in low nutrient environments (Tindall & Morton, 1998; Shears &
Ross, 2009; Pistocchi et al., 2011).

In addition to being well adapted to oligotrophic conditions, mixotrophy
cannot be discarded. The presence of red bodies in many cells of Coolia or
Ostreopsis is frequently reported (Aligizaki & Nikolaidis, 2006, Selina & Orlova,
2010) and could represent an effect of mixotrophy although this has not been
proven. These bodies were observed only in field samples, but when the cells with
these bodies are isolated and grown in artificial inorganic medium, the bodies
disappear (Authors personal observations).

In the Mediterranean Sea, Ostreopsis blooms in summer
(Mangialajo et al., 2011; Vila et al., 2001) when nutrients are relatively low and
light and temperature are high. In all cases, it is clear that when Ostreopsis blooms
the water is warm although in some cases the bloom may occur after the
temperature maximum (Selina & Orlova, 2010; Totti et al., 2010). High water
temperatures, high irradiance and high remineralisation are factors that converge
to create an environment favouring benthic HABs.

One more paper that makes it clear that Dinos are really not limited to NO3 and PO4 but have ways to thrive on untestable organic forms of N.
Putting the N in dinoflagellates

This suggests that when N is limiting, uptake of different forms will be favored over strict assimilation of NH+4 which has a reduced energy cost. Curiously, different blooming populations of dinoflagellates were found to have high uptake rates for urea and/or amino acids, and these rates were always higher than the rates for NO−3 uptake (Kudela and Cochlan, 2000; Fan et al., 2003; Collos et al., 2007). In L. polyedrum, the urea uptake rate was also about 2 times more than that of NH+4, even if environmental urea concentrations were less than NH+4 (Kudela and Cochlan, 2000). Taken together, these observations suggest that dinoflagellates possess a full suite of transporters for inorganic N and organic N forms, that they have the biochemical means to assimilate these N forms, and that they show a great physiological plasticity in response to external N types and concentrations.

Dinoflagellates are able to store large amounts of inorganic and organic N forms. Comparison of N uptake and assimilation rates at various growth rates in A. minutum showed that most of the NO−3 and NH+4 taken up in 1 h was not assimilated, and it was hypothesized that the unassimilated N was stored within the cell (Maguer et al., 2007). This species was also found to have a great storage capacity for amino acids (Flynn et al., 1996), and a similar storage capability was also described in A, catenella, A. tamarense, and Amphidinium cartarae as well as other unicellular algae (Dortch et al., 1984; Collos et al., 2004; Fauchot et al., 2005).

It was long believed that bacteria were too small to be ingested by dinoflagellates. In the last few years, however, fluorescence and transmission electron microscopy observations revealed that multiple HTD[heterotrophic dinos]s and MTDs [mixotrophic dinos - our problems] were able to feed on heterotrophic bacteria and cyanobacteria (Jeong et al., 2005a, 2008; Seong et al., 2006; Glibert et al., 2009).

There are many caveats and qualifiers, but the fundamental issue is that the lack of water NO3 and PO4 may be fatal for some rather harmless algae, but for our problem dinos, all of which are photosynthetic, benthic, toxic - these low inorganic forms of N and P are a circumstance they are well adapted to. (as long as you keep feeding your fish - providing organic N and P inputs.)

 

[Randy Holmes-Farley]

Thank you everyone for your replies. So far I am not convinced.

If the whole idea is simply that certain organisms can suddenly prosper because they utilize certain nutrients more so than others and can outcompete other organisms because the organisms now lack a certain specific nutrient, then sure, that is fully understandable and is exactly what would be expected.

No one here is saying there is proof, but that is the only plausible idea for the effect that is clearly seen with dinos becoming a problem at low nutrients.

 

[Azedenkae]

Thanks everyone. So it just boils down to metabolic differentiation and urgo outcompetition by certain species when nutrient conditions change. Nothing strange or wonky here then, good to know.