La cause des algues

amphioxus a écrit:
ils ne sont pas con certe, mais si c'est la première hypothèse alors ce sont eux qui nous prennent pour des...

et si c'est la deuxième hypothèse, l'enjeux est-il si important que ça ? on parle de quoi là, d'aquariophilie ou de recherche nucléaire... :##06:
vous voyez ou je veux en venir...

Qu'ils ont copiés sur une autre recette peut-être ?

tilho a écrit:Et puis même sans nous donner la composition de leur raclures d'égouts, ils pourraient argumenter leur théorie divine non ?

Spoiler:

Folks,

For a while now I've been chasing the idea that at least some algae
problems can be related to organic compounds in the water. The general
thinking goes like this:

1) Some (but not necessarily all) algae can live in the dark by using
glucose and other soluble organics in the water.

2) Aquatic plants "leak" soluble organic material into the water.
There's even some published speculation that this behavior evolved to
encourage attached algae communities (herbivores would then eat the
attached algae, and leave the plant alone).

3) Terrestrial plants, when deficient in nitrogen, phosphorus or sulfur
can photosynthesize, but fail to use the simple sugars produces by
photosynthesis; instead, the sugars accumulate in the plant and lead to
anthocyanin (reddish-purple pigment) in the leaves and stems.

4) Aquatic plants should behave under nutrient stress like terrestrial
plants, but I reason that rather than accumulating the sugars, they will
probably leak the sugars back into the water. This leaking may help
explain why I don't usually see anthocyanin buildup in aquatic plants
that otherwise seem to be deficient in nitrogen or phosphorus. It's
perhaps interesting but irrelevant that stressed algae leak large
amounts of soluble organics.

5) Algae are more efficient than plants at concentrating dissolved
nutrients, so in the case where both plants and algae depend on the same
nutrient supply, nutrient stress and loss of organics should effect
plants before it effects algae.

6) The sugars lost by a nutrient-stressed plant can be used by algae; it
will act as a suppliment for the algae and allow them to grow at rates
and under conditions (low light, in particular) where they wouldn't
normally thrive.

If the last item could be proven true, then we might be able explain
some of our toughest algae problems, and in particular might explain how
it is that we can make algae disappear by fertilizing an aquarium.
Well-nourished plants stop losing sugars and without the extra subsidy
from the plants the algae no longer thrives and start to disappear.

So that's the theory. Of the items above, 1-3 are supported in the
scientific literature. There's a problem with applying item 1 (see
below), but otherwise I'll just regard 1-3 as facts.

Item 5 is also supported in the literature, but the case where both
plants and algae are dependent on the same nutrient supply is fairly
hypothetical. It generally doesn't occur in nature where plants use a
supply of nutrients in the soils that isn't available to algae. It
comes close to being true in aquariums where the principle nutrient
supply is added to the water column.

Item 4 is supported qualitatively by my own observations. It could be
supported more quantitatively by monitoring DOC (Dissolved Organic
Carbon, or just adsorbance at 254 nm in a spectrophotometer) in a
planted aquarium. If correct, then DOC in an aquarium should be low
when the plants are completely nourished and should be higher when the
plants are deficient in nitrogen or phosphorus. A more rigorous support
would be possible by determining the actual sugars in solution, but that
would be more difficult.

Item 6 is the conclusion. It could be supported by proving item 4 and
showing that algae growth rates and occurance correlate statistically
with the changes in DOC in an aquarium.

One of the weaknesses of all this reasoning is that we don't know if our
common nuisance algae actually can use simple sugars; that's the problem
with appying item 1. So last week I set out to see if some of our
common nuisance algaes can use dissolved sugars. I only have a few in
my tanks, so that's what I used.

I set up two 1-quart bottles in a simple controlled experiment. Each
bottle was covered in duct tape to exclude light. One was filled with
dechlorinated tap water and the other was filled with dechorinated tap
water plus 1/24th of a 5 gram glucose tablet -- about 200 mg of
glucose. The water in both containers was changed every two days.

I took three algae samples from my tanks and split them more-or-less
equally between the containers. One algae sample was a green,
long-stranded hair algae that grows unattached in a sunlit bowl with my
emersed sword plant. One algae sample was a short-stranded green hair
algae that grows in bright artificial light or dim light and forms
loosely attached, dense mats on the substrate and tufts in protected
areas on leaves and aquarium equipment. The last sample was black brush
algae. This is a red algae that grows under bright or dim light (but is
more characteristic of dim light) and is firmly attached.

I placed the bottles in a cabinet, put an air stone in each container
and bubbled air through them for a week. I observed the contents of
each bottle every day. Today (a week after starting the test) I dumped
the bottles to see what I had left.

There were several problems with the experiment. Mostly, the agitation
caused by aeration made the hair algaes get matted and entangled.
Future attempts need to use less agitation and keep the samples
separated. Second, I didn't have any way to measure or weigh the
samples and hoped for clear-cut results such as the complete
disappearance of the failed samples. That didn't happen, so any
conclusion depends on my recollection of the sample size and a
comparison of the samples. Finally, the glucose concentration probably
needs to be smaller to more nearly represent conditions in an aquarium.

So, after it was all done, here's what I noticed and what it might mean.

I half-expected that one or both bottles would be taken over by blue
green algae. That didn't happen, and I'm not sure why. That may
indicate that whatever BGA accompanied my samples didn't use glucose. I
find that a little surprising.

The long-stranded hair algae in both bottles was smaller than it started
out to be. That could be just because it was matted and twisted by the
aeration, but my sense is that there was about a 50% loss of mass in
both bottles. This would indicate no response to glucose. This doesn't
surprise me much, as in my tanks the algae occurs only in bright light.

The short-stranded hair algae disappeared completely from the bottle
without glucose. Most of the sample appeared to break up into loose
fibers after the first 24 hours of the test. Some of the short-stranded
algae may still have been present but unobserved at the end of the
test. If it was present then it was tangled with the long-stranded
algae. The short-stranded hair algae was still present in the bottle
with glucose. It was loosely attached to the bottom of the bottle and
appeared to have at least as much mass as it started with. This
suggests that the short-stranded hair algae did use the glucose.

The black brush algae was still clearly identifiable in both bottles,
but in the bottle without glucose it appeared to lose about half of its
mass. Some of that BBA sample could have become entangled with the long
hair algae. The original mass appeared to be entirely intact in the
bottle with glucose, but it didn't appear to grow. So BBA appeared to
use the glucose.

There are enough problems here that I can't draw any real conclusions.

Ideally, if better experiments in the future prove out the results of
this test then we will have not just an explanation for some of out
sticky algae problems, but a new approach (organics control) for
cleaning up and controlling nuisance algae.

Roger,

That was an interesting post a couple of days back.
I've been trying to digest it. I'm out of my element
with most of this discussion, but wanted to comment.
In a discussion with friends, it was pointed out to me
that plants (which includes algae) can make use of
sugars, amino acids, etc. - it is the basis of tissue
culture.

You are referring to a nutrient stressed situation.
I’m assuming that you are referring to high light tank
with co2 supplementation and without adequate nutrient
supplementation, because most “planted fish tanks”
have an abundance of nutrients. The low tech planted
fish tank is where most folks experience algae
“problems”. But again, you are talking about a
nutrient stressed situation.

You mention that the plants might be leaking sugars
into the water, which makes this sugar food source
available for algae to use. This is difficult for me
to follow, but certainly, I’m not saying that you are
wrong. During lean times when plants are nutrient
stressed you conjecture that our plants begin to make
sugars as terrestrial plants do. I would think that
the plant is making sugar for its own use. The plant
controls the water flow into and out of the tissue.
If the sugars leak then wouldn’t it be in miniscule
quantities? The sugars need to be leaked by the
plant and absorbed by opportunistic algae. This is a
byproduct of a byproduct, as it were. Would this
effect be measurable in an aquarium?… I would think
that the bacteria bed would make use of the sugar
before the algae would.

Thanks for sharing your post with us.

"That was an interesting post a couple of days back. I've been trying to digest it. I'm out of my element with most of this discussion, but wanted to comment."

Thanks for taking the time. I hoped to get enough feedback to see if I
needed to change my thinking.

"In a discussion with friends, it was pointed out to me that plants (which includes algae) can make use of sugars, amino acids, etc. - it is the basis of tissue culture."

The ability of plants (and algae) to take simple carbohydrates out of
solution is also the basis for Seachem's Excel product. While I have
found plenty of references that indicate *some* algae will use sugars that
they get out of the water I haven't found any author willing to say that
they *all* will. I expect conciderable variability.

As a note, I'm using the term "sugar" to refer to most simple
carboyhydrates.

"You are referring to a nutrient stressed situation.
Im assuming that you are referring to high light tank with co2 supplementation and without adequate nutrient supplementation, because most planted fish tanks have an abundance of nutrients. The low tech planted fish tank is where most folks experience algae problems. But again, you are talking about a
nutrient stressed situation."

Specifically I'm referring to planted tanks low in nitrogen and/or
phosphorus. This could be high or low in other factors, though the
problem is likely to be more evident in tanks where there is a high rate
of photosynthesis.

"You mention that the plants might be leaking sugars into the water, which makes this sugar food source available for algae to use. This is difficult for me to follow, but certainly, Im not saying that you are wrong."

As near as I can tell from the literature it is well-known that aquatic
plants do leak organics into the water. There may be an evolutionary
advantage to that behavior.

"During lean times when plants are nutrient stressed you conjecture that our plants begin to make sugars as terrestrial plants do. I would think that the plant is making sugar for its own use. The plant controls the water flow into and out of the tissue. If the sugars leak then wouldnt it be in miniscule quantities?"


All plants (aquatic or terrestrial) and algae make sugars any time the
light is bright enough. Simple carbohydrates are the initial product of
photosynthesis. The plant normally builds all of its components out of
those simple sugars. Phosphorus is necessary in the intermediate steps of
carbohydrate synthesis and for the plants to make proteins and other
biochemicals they need other nutrients as well. That's were nitrogen,
more phosphorus and most of those other essential elements fall in.

If nitrogen or phosphorus is deficient then the plant can't make proteins
and other classes of biochemicals and the excess simple sugars build up.
Some of the sugars can be converted to woody material and some can be
stored, but not all of it. In terrestrial plants the excess sugars build
up; I think that after some point aquatic plants tend to lose the sugars
rather than retain them. Terrestrial plants might leak them too if they
could, but they since they aren't emersed in water it isn't so easy for
them to lose the sugar.

I have never read of a mechanism by which a plant could effectively slow
down the rate of photosynthesis, so the simple sugars are produced
regardless of whether the plant needs them, can use them, or has any way
to store them. Even detached leaves will continue to photosynthesize. At
some point the plant must start leaking those sugars back into the water.
The leakage rate would not be miniscule; the plant could potentially leak
all of the sugars that it synthesizes.

I think I've seen that happen in phosphate-deficient vals. Given CO2 and
light they bubbled and bubbled, which is direct evidence for
photosynthesis, but despite the evident photosynthesis there was no
evident growth for weeks. Where did they put the products of their
photosynthesis? Vals don't have noticable storage organs and there was no
anthocyanin evident in the leaves to indicate sugar buildup in the leaves.
I concluded that the plants leaked almost everything they
photosynthesized. There were concurrent algae problems.

"The sugars need to be leaked by the plant and absorbed by opportunistic algae. This is a byproduct of a byproduct, as it were. Would this effect be measurable in an aquarium? I would think that the bacteria bed would make use of the sugar before the algae would."

The "leaked" sugars could represent a big part -- even all -- of the
plants primary production, so this is a potentially major process, not
simply a byproduct of a byproduct.

The opportunistic algae are another matter entirely. Algae are highly
evolved specialists. The algae that live in our tanks probably have some
specific adaptation that allows them to thrive under aquarium conditions.
Out of all the thousands of algae species out there, there are only a few
that thrive to nuisance levels in our tanks. I suspect that the ability
to use dissolved sugars is one of the factors that determines which algae
species thrive in our tanks. So the algae aren't merely opportunists,
they are specialists at exploiting the conditions we provide them.

You are right that bacteria should be able to out compete algae for the
dissolved sugars, and in a natural environment that is probably what
happens. At least that is what I was told by a biology professor at the
local University who has a special interest in organic compounds in
natural systems.

We aren't dealing with natural conditions. Instead I'm talkin about
pathologic conditions brought on by nutrient stress in a mostly closed
environment. I think the availability of those sugars would be so high
that competition would be irrelevant. The sugar would be available to
both algae and bacteria.

This theory isn't really a "revolution" in thinking. Instead it's just a
different way of explaining a number of observations that are otherwise
difficult to understand; like how it is you can add nutrients and
discourage algae, which lots of us have found to work.

Along the lines of your hypothesis, I came across this interesting article
on a genetically engineered algae. It looks like they are taking algae's
natural ability for specialization and the ability to utilize simple sugars
one step further through genetic manipulation.

Scientists at a company in Columbia MD and Palo Alto CA have engineered a
new micro algae that uses glucose as its primary energy source instead of
sunlight. That's right this stuff grows in the dark! They accomplished it by
splicing a human gene that directs the cellular flow of glucose into the DNA
of an existing algae. Here is the link to the story

I guess there's a lot of money in that field right now. Now we have
genetically engineered algae that can get diabetes!

I've read about naturally occuring algae that lost the ability to
photosynthesize, and so are completely dependent on sugars they can get
out of their environment. They're called "leucophytes"; they have all the
internal structures that normal algae have (chloroplasts, in particular)
but no chlorophyll or other pigments.

laurentD a écrit:C'est bon, je compte sur toi pour traduire le machin ^^

laurentD a écrit:
Ce résidu de discussion date de 2001... Depuis cette date, rien...

laurentD a écrit:Scientists at a company in Columbia MD and Palo Alto CA have engineered a
new micro algae that uses glucose as its primary energy source instead of
sunlight. That's right this stuff grows in the dark! They accomplished it by
splicing a human gene that directs the cellular flow of glucose into the DNA
of an existing algae. Here is the link to the story[/i]

tilho a écrit:Laurent parlait du dosage des ingrédients, pas du dosage du produit final à utiliser en aquarium !

amphioxus a écrit:

laurentD a écrit:Scientists at a company in Columbia MD and Palo Alto CA have engineered a
new micro algae that uses glucose as its primary energy source instead of
sunlight. That's right this stuff grows in the dark! They accomplished it by
splicing a human gene that directs the cellular flow of glucose into the DNA
of an existing algae. Here is the link to the story[/i]

ben moi je ne retiens que ça...

purée laurent t'avais ça sous le coude depuis longtemps ?

bon, j'imagine que cela explique les algues sur le bord des feuilles.

reste plus qu'a expliquer les autres