Nutrients and eutrophication

[parotet]

After Wikipedia, Eutrophication (Greek: eutrophia—healthy, adequate nutrition, development; German: Eutrophie) or more precisely hypertrophication, is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system. And as far as I know, Phytoplankton blooms, which contain algae, are the main consequence...

If I have leant something in this forum and experienced in my tanks during the last months it is that ferts do not cause algae, but a more complex combination of different things such as light, CO2, flow, filtration, etc. that have to be balanced.

So what is what am I missing here? After this explanation, and others I have read, the excess of nutrients leads to algae blooms...
I'm sure there's something I don't know and you can explain to me.

Cheers,
Jordi

 

[Tim Harrison]

Not entirely sure what the question is. But as far as I know it all appears a bit random really and not particularly that well understood - eutrophication that is...not your post.
Apparently, similar nutrient loads will not necessarily have the same effect on a different environment or the same environment at a different point in time. This is because eutrophication is just one mechanism that causes algal blooms. The impact of excess nutrient loading also depends on many other biotic and abiotic factors, such as algal species composition, their nutritional state at the time of loading, the existence of grazers and the physical features of the environment.
Changes in nutrient ratios also play a role particularly N : P, as does the ratio of dissolved organic carbon and dissolved organic nitrogen - that's perhaps why good tank maintenance and inorganic nutrient dosing help to reduce algae.
Another factor is the physiological strategies that groups of algal species use to acquire nutrients such as, believe it or not, heterotrophy, and mixotrophy.

 

[parotet]

Thanks Troi, I understand that another consequence of eutrophication (at least in the lake beside my hometown) is that the visibility is nearly reduced to cero (well a few inches under the surface you cannot see a Secchi disk, but that is like 0). This reduce any chance of growth for macrophytes that can help to oxygenate the water, creates anoxic areas that difficult life, affect to nutrients ratios, the autochthonous fish fauna (killies from genus Aphanius and Valencia) is replaced by invasive carps that eat any plant that grow... but I guess all these things are a consequences that worsen the eutrophication process and makes very difficult to go back to a "healthy" state of the water body.
But once again, what puzzles me, is that it seems (though I may be wrong) that high phosphates levels induce eutrophication and algae growth. Why is it different in a tank?

 

[Edvet]

Dosing with PO4 | UK Aquatic Plant Society See Darrel's comments and link

 

[parotet]

Thank you Edvet, very interesting reading but I keep on having troubles to answer my question...
I can read a post from Darrel saying:

"This is true on one level, I spend a large proportion of my time trying to reduce eutrophication of natural ecosystems. The whole environment is awash with unnatural levels of nitrogen and phosphorus, and it is a major cause of environmental degradation. Phosphate stripping, using Fe(II) ammonium sulphate as a precipitant (this is very effective removing about 95% of the phosphate), was introduced to deal with problems caused by optical brighteners in detergents, sewage etc. The orthophosphate (PO4---) ion naturally limits productivity (along with NO3-) in many aquatic systems. Add non-limiting amounts of PO4--- creates huge blooms of planktonic green algae (Chlorophyta) "Green water", which then die of in the autumn as PAR (photosynthetically active radiation) and temperature decline. This decay adds a huge amount of biochemical oxygen demand (BOD) to the water, de-oxygenating it, killing and/or altering its biota. Once the phosphate is present in the ecosystem it remains bound to clays (they have AEC - Anion Exchange Capacity), and as largely insoluble phosphate compounds, and this reservoir will then supply enough PO4--- (orthophosphate ions) to repeat the whole process again and again. But, it isn't applicable to aquaria. The levels of phosphorus in an aquarium will always be high enough to support algal growth, unless we take extreme measures (100% total RO water changes, chemical adsorption) to remove it."

So it looks like adding unnatural levels (=very high) of N and P creates algal blooms, which is just the opposite I have learned and experienced in UKAPS: add nutrients if you don't want to have problems with algae. Actually the correct statement should be: add nutrients to your tank so they are unlimited for plants if you don't want to have problems with algae. So... is it just a matter of what can be considered "unnatural levels"? (I mean, one thing is to add unlimited amounts for plants, but maybe the amounts that cause eutrophication are much much higher?)

Furthermore, Darrels says:

"Telling a planted tank keeper that you can use phosphate control to control algae is untrue, and I stand by that"

IME, not adding phosphates means no plant growth, means algae, etc.... or do you mean that you cannot reduce phosphates as a way to control algae? In that case, it would make more sense.

Mates... I need an explanation. Thanks in advance Darrel and apologies if you don't agree with copying here your post from other forums.

 

[Edvet]

I am far from the experts knowledge wise, but the way i see it is "balance". According to Liebig's law growth is reduced by the lowest growthfactor. EI adds everything in abundance, so in our tanks with relative lots of light we add to make sure everything is available (for optimal plantgrowth of the species we have in the tank). In nature: flowing water adds nutrients all the time, and we only see growth nature permits (only species which can grow in that situation). Overdosing of one thing will cause unbalance: growth of unwanted species.

 

[OllieNZ]

Add loads of light to your tank (midsummer sun) without upping co2 levels. No amount of nutrients will save you. As darrel says about the green water dying off in autumn once the PAR levels drop, the nutrients are still there its just the conditions no longer favour algae growth. It would be incorrect to say our tanks are unlimited as we always limit light.

 

[dw1305]

Hi all,

This reduce any chance of growth for macrophytes that can help to oxygenate the water, creates anoxic areas that difficult life, affect to nutrients ratios, the autochthonous fish fauna (killies from genus Aphanius and Valencia) is replaced by invasive carps that eat any plant that grow... but I guess all these things are a consequences that worsen the eutrophication process and makes very difficult to go back to a "healthy" state of the water body.

That is pretty typical of the situation over large areas of the world.

Thanks in advance Darrel and apologies if you don't agree with copying here your post from other forums.

No problem, the link is this one <British Cichlid Association &bull; The place to talk about the Cichlids in our Aquaria>, and I still agree with everything I wrote in the thread (and linked threads).

It would be incorrect to say our tanks are unlimited as we always limit light.

I think this probably is the reason, together with the fact that our tanks are shallow and filtered. The problem in natural situations is that un-natural green or filamentous algae blooms stop the light reaching submerged macrophyes, which then die. This then leads to a situation where all the PAR (and nutrients) are available for algal growth.

cheers Darrel

 

[parotet]

Thanks Darrel, so the correct statement should be "adding nutrients/phosphates to a planted tank don't cause algae just because we can keep plants on them (something which won't happen in a uncontrolled/natural ecosystem)", isn't it?
Simple but stunning...

 

[ceg4048]

The impact of eutrophication is so much broader than just whether you get algae or not.
People have traditionally assumed that the key element of eutrophication is PO4, when in fact there are a lot of other components to the agent or agent that cause the eutrophication.

There are many natural eutrophic systems. In those systems algae is not dominant. So, "nutrients not causing algae" is not only valid for our tanks.

Eutrophication of ordinarily oligotrophic systems results in a change in the outcome of the race for nutrient gathering. As organisms compete for resources in an oligotrophic environment, the lack of nutrients evens the field and prevents those organisms which are adept at gathering nutrition from dominating. When nutrients are introduced into those low nutrient systems the adept organisms will then have an advantage.

Depending on the system, it will either be higher forms or lower forms that gain an advantage. It won't automatically be algae.

The Everglades is an example of an oligotrophic system where ordinarily, algae is the dominant species. That means that greater than 50% of the biomass in that system is algae, naturally. It has been observed that eutrophication of this system results in a decrease in algae biomass and the rise in biomass of non-algal plant species and the decline of other plants.

In other systems, eutrophication results in greater algal biomass. The systems are very complicated so it's not easy to draw any correlation between the adding of nutrients and the rise of algae.

In our tanks the species of algae are not the types that care very much about the nutrient load. The blooms occur as a result of predatory behavior, not due to eutrophication. So there are many facets to the behavior of algae. Their behavior in a non planted tank may differ than in a planted tank. What we observe is that in the tank, the presence of plants affects the behavior of algae, and the presence of algae affects the behavior of plants.

Cheers,

 

[plantbrain]

Too many aquatic weeds= bad. Too few= also bad.
Too much algae= bad, too little, also bad.

The man made issues: way too much waste added to natural and man made systems with FAR fewer control points than an aquarium. You cannot control a lakes CO2 or O2 or light or temp routines without a massive input. So nutrients, mostly P and sometimes N are mostly the main options.

Unlike the EU/UK, we kill aquatic weeds pretty aggressively here in the USA.
One of the biggest questions around is after you kill them, what do you do then?
Most times, you get pea soup.

Restoration of native macrophyte beds is a little studied research area.

I've always held that nature knows best if you are willing to let it do it's thing and get the ball rolling.
An excellent example in Florida is the Ichnetucknee River State park. 35 years ago is was a PO4 mining company and was trashed.
Today, it's a jewel of a state park in Florida. These places can be restored to a really wonderful level if people just leave things alone and get them started right.

Plant tanks are no different. We load the aquarium with a lot of new plants and are basically restoring/creation is a better term) and nice macrophyte bed.
It takes a lot of effort initially to get things growing well, but then it's much easier after things fill in nicely.
Thus the plants/macrophytes define the system, not the nutrients. If you stop caring for the plant...........well.........they do not grow so well, and then you get algae.
Natural plant beds are great for most water users interested in natural systems. Fishing particularly. Agriculture? Not so much. Dams? Also, not so much.
Like most things, there's plenty of pros and cons/trade offs.

In areas where there's lots of aquatic weeds, adding more waste= more aquatic weeds.