N limitation vs P limitation

[Curtswearing]

Nitrogen is highly unlikely to be limiter in our tanks unless you had an extremely low bioload and had a massive skimmer and great maintenance practices. However, I found this article (which requires Adobe Acrobat) extremely interesting.

N vs P as a limiter to algal growth

Basically, they found that in the Hawaiin reefs, they are oligotrophic based on two limiters. It was originally thought it was only P that was the limiter but (at least in this area) N was also a limiter.

I don't know if this follows in other reef areas but it tells me that I should not only limit my introduction of P and do my best to skim out what I can, but I should also be careful with nitrogenous compounds as well if I want to avoid algae. Luckily, the same things that I do to avoid problems with P will help me with N.

 

[NaH2O]

OK - let me first put out there the date of this study was 1997/1998 - I don't know if this is old in the marine biology world, and maybe there has been further studying on these factors that we don't know about.

Does this study pertain to reef aquaria? I'm not sure. I do know that when Phosphorous is removed from a tank, then algae seems to begin to die off. I noted that in my own tank....with a semi-high nitrate reading. Nitrogen products will be available in our tanks....it seems like fact. There is usually at some point a nitrogen product being broken down or converted, and I'm sure the algae is excited about having the opportunity to utilize that....be it ammonium, nitrite, nitrates. We know that excess nutrients of any kind will fuel an algae bloom - that is why on the reef, if algae is growing in abundance, then nutrients are coming from somewhere......

In each of the macroalgae species assayed, specific growth rate in either ammonium- or phosphate-enriched seawater was significantly higher than in unenriched seawater.

OK - that makes sense.

Basically, we need to monitor our inputs and water quality to keep on top of excess nutrients. However, nitrogen and phosphorous will encourage macroalgae to grow in a refugium.....but then you have a whole different ball game to deal with .

 

[mojoreef]

Interesting topic.
Here a way of looking at it as it relates to our reef tanks. With fods, salts additives and so on we basically introduce quantities of both N and P. Both sources to a point are limiting, as in if you totally eliminate one or the other things will die. However thier are organisms that can create thier own nitrogen so that one is not as limiting.
Once these products enter the reef tank however the equation dramatically chances. So lets taka quick peek at both as they travel through our tanks.
N= enters the tank and is immediately attacked by bacteria which reduce it from Ammonia to nitrite then pass that down and it is further reduced to nitrates, then passed further down to where it is converted from nitrates to N gas or ammonium. In the case of the N gass it is off gassed, and in the case of ammonium it is recycled.
P=enters the tank and is immediately attacked by bacteria and other simular organisms. The bacteria however dont reduce it, they change its form (say from inorganic to organic and/or solid to dissolved) but beyond this it is only reduced a tiny bit as energy/heat.
So if we take a look at the path of these to products (N,P) we can see that not only can our tanks deal with N alot better but we see that N can be produced by organisms with out it being put in the tank (cyanobactor and other simular).
P on the other hand will be used up by the tank but very slowly and has to be introduced in order for it to be thier in the first place.

On the study linked I think that this statement says pretty much everything

These results suggest that, in order to persist in low-nutrient
coral reef systems, some macroalgae require high rates
of nutrient advection or access to benthic nutrient
sources in addition to nutrients in the overlying water
column.

mike

 

[Curtswearing]

Great points Nikki and Mike.

 

[Craig Manoukian]

Very good reading and comments Curt, Nikki, and Mike!

 

[EvilMel]

It's pretty interesting that they are talking about N and P but only a slight mention about Fe.

So there is a theory of co-limitation by N and P, which if I am not mistaken (and I could be) goes like this: enzymes which are necessary to utilize P contain N. If the organism can not make the enzymes necessary to use P (say in the process of making new DNA or cell walls), then it appears P limited when it actually could be N limited.

There's a ton of stuff out there arguing for N limitation, P limitation, and Fe limitation, and also even S limitation (of diatom growth). I actually did my graduate work on examining the effects of Fe on bacteria and phytoplankton in marine systems. Let me tell you, there's a TON of stuff out there on a million topics of this sort (many which are more current, I hope that doesn't sound negative at all).

 

[mojoreef]

LOL Mel no kiding, to tough to make a call for sure in the wild. So many critters have evolved differently to adapt to enviroment or to create their own. Whats your thoughts on how it pertains to our tanks??


Mike

 

[EvilMel]

Well, honestly in our tanks I think that most of the nutrients are in high enough abundance as to NOT be limiting ever. I mean if we had that little nutrients, how would our corals grow? The zooxanthellae in them need some nutrients, right?

So I don't know that this article is really all that applicable to our tanks. It is good to see that people on here are reading scientific articles.

 

[Craig Manoukian]

I mean if we had that little nutrients, how would our corals grow? The zooxanthellae in them need some nutrients, right?

Great point Mel! The trick is to have just the rigt amount available.

 

[NaH2O]

in our tanks I think that most of the nutrients are in high enough abundance as to NOT be limiting ever. I mean if we had that little nutrients, how would our corals grow? The zooxanthellae in them need some nutrients, right?

I agree. I think there will always be nutrients in our closed systems - there seems to always be an input. Perhaps the type of corals would be a better judge as to how much nutrients are allowable before calling them limiting? Softies, LPS, vs. SPS - aren't the nutrient demands different??

 

[Craig Manoukian]

As mojoreef has explained to me, and Nikki you hit the nail right on the head, the animals we keep in our tanks do live in different places in the natural reef where the nutrients, water flow, lighting, etc. are slightly different. For example my 80 gallon tank with a DSB is a perfect environment for softies and clams with 350 watts of 10,000k MH lighting. Mike's 700 gallon tank with a bare bottom and different lighting is perfect for SPS. The N and P requirements of each tank are different and specific to the inhabitants. The art is getting them just right and exporting what is not needed, eh?