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Re: algae

> Tom wrote:
>> A plant needs a lot more of a nutrient ( say NO3) than the algae does. The
>> plant gets stunted at 1ppm or less for more than 3-4 days(a general range
>> for most plants). The algae just slows down but can still look bad.
> <snip>
>> Some glass algae can persist in absence of P. Plants certainly grow better
>> than algae can due to obtaining P etc from the soil(bacterial lysis etc &
>> PO4 complexes etc) but the algae can live on virtually nothing. Algae can
>> concentrate P at very low levels. Fish food is enough of a source for algae
>> to respond and grow to nuisance levels... but not the plants. Riccia
>> certainly does quite well with enough PO4. A number of other "difficult
>> plants" do very well in higher PO4 levels.
> This makes it sounds like the now venerable idea that aquarium plants
> will out-compete algae for low nutrients is actually wrong.  If algae do
> better at low nutrient supplies, then that competition will always be
> won by the algae.

That's kind where I'm heading. Heck many of us have tried a number of
combo's and tested down to nub so to speak and the damn algae won't submit
that way but does submit when the plants are taken care off well, from a
nutrient standpoint. At least that's what I keep seeing again and again.
> Under natural conditions plants usually dominate over algae when the
> dissolved nutrients are low.  That's the opposite of what you seem to be
> saying here.  Of course, under natural conditions the plants are rooted
> in a rich substrate and get most of their nutrients through their
> roots.  It's only the algae that suffer poor growth because of low
> dissolved nutrient levels.

Natural conditions vary greatly. Our tanks vary as much as we let them. Many
plants and algae would be pushed to competitive exclusion if things remained
the same in nature. It's that variation that allows more niches to exist and
more diversity. We can create our own niche here. I won't give up on that
part, perhaps the limiting notion but a "range" perhaps may be a better term
for this. 
> Under conditions with high dissolved nutrients algae usually dominate
> over plants because plants lose the competition for light, not the
> competition for nutrients.

Not duckweed, floaters etc.
> Most of use don't use a rich substrate and our aquarium plants have to
> compete head-to-head with the algae for dissolved nutrients.  There must
> be something in our aquariums that tilts the advantage to the plants,
> because with the same nutrient levels under natural conditions the algae
> will usually squeeze out the plants.

What exactly is this thing though. I've tried the highest lighting and rich
substrate with little water column nutrients. I've tried the water column
heavy approach as well with high light again. Got better results with the
water column..........it doesn't match but then again we are adding CO2,
stable nutrient supply etc
>> Most of the algae we hate has very efficient size ratios compared to the
>> higher plants. They can grow faster since there's less issue of transport,
>> most of the algae is a photosynthetic machine, no roots/xylem/flowers etc
>> that don't contribute to the production of plant mass. So it's ALL algae
>> production. We don't see the plants roots, xylem and other parts of the
>> plant. We see algae.
> Not all advantages go to the algae.
> The other thing that we don't see is that algae have relatively high
> energy and material demand compared to plants.  Phytoplankton don't just
> float around all day; they swim, and that takes energy.

Green water does and so do BGA's. Most that bug us are attached or entangled
like Cladophora. Their gametes swim (in most cases) though, but that's no
big deal.  

> Diatoms and
> other algae that build biofilms produce fairly large amounts of slime
> that they exude around themselves; that takes both energy and carbon.

The musilage is quite interesting in and of itself though from a biochemical
standpoint. Bacteria produce a similar matrix that acts a substrate in
pelagic systems in the Ocean. Quite cool. But that musilage can act as a
deterrent from other epiphitic algae attachment. Not a bad investment I
guess but it slows them down some.
> Even the alga that don't do these things still have to build up and
> maintain all of the metabolic "machinery" necessary to maintain life
> within a single cell; specialization is limited and I imagine that
> metabolic efficiency is limited along with it.

But less so than a plant? Or more so? Some plants like our fav Bryophyte,
Riccia is fast to respond to nutrient level influxes. But a more reserved
plant, say a crypt or a runner plant may take it's sweet old time. Those
roots take time as well to get going.
> Plants, on the other hand, are sedentary.  They don't swim.
> Non-pathologic plants exude some material (mostly through their roots)
> but nothing that compares volumetrically to the slime produced in a
> biofilm.  And of course, plants have highly specialized tissues and I
> suppose they should have higher metabolic efficiency as a result.

Most of those tissues are adapted to above water and then they reinvaded the
water, regressive evolution if you will..........like blind fish, beetles,
ampipods, etc cave fauna. This has happened a number of times over the eons.
Back and forth co-eviolution. The Ultricularia's are quite advanced and
others are as well but most are simpler plants, like the moss, Riccia,
horwort, floaters etc. Some do have some advanced traits, ie aerenchyma, but
it's a mixed bag.........

>> But since algae can live in low and in high levels of nutrients and are
>> seeming more efficient, why do the plants continue to dominate? Algae is
>> still there but it's not dominating. There's plenty of nutrients for the
>> algae as well as the plants. Why then is this happening? It seems like a
>> contradiction.
> I agree, but I wonder if the advantage has much at all to do with
> nutrients.  

That's what I think to a degree, how much? Less than being said often on
list IMO.

>Most algae (except the low-light specialists) may require at
> least brief periods of high-intensity light in order to get the energy
> they need to function; long periods or relatively low light may not be
> enough.  The result would be that our tank conditions lead to the
> selection of only a few, specialized algae.  You don't have to get very
> much direct sunlight on an aquarium before you see drastic changes in
> the type of nuisance algae that grow in the tank.

I had a sunlight tank that got the light for awhile. BGA was common along
the gravel line was about all I noticed. My C parva flower submersed that
way. Alga eand plants have much of the same access. Some plants can block
the algae and some algae can block the plants. In stable places, often I've
seen plants in clear water. Unstable, few plants, more algae. Same in a
tank. I've had good luck with lower lighting but it goes back to the car
analogy, faster higher lighting causes worse accidents if anything goes
wrong. Is it the light or is it the speed at which your driving the nutrient
> Algae are also subject to far higher grazing pressures than plants.

Well in our tanks! I have big grazer hands.

> Especially in our tanks, where the grazing species are selected so that
> plant grazing is discouraged and algae grazing is encouraged.  Algae
> grazing isn't limited to the macroscopic grazing we see and promote.  It
> also occurs on a microscopic level.  Some protozoans, for instance, feed
> on algae.

How much do they contribute to our tanks though? Good question there.
>> Perhaps the tide is only tilted when there's a nutrient that too low rather
>> than this popular "excess nutrient" idea.
> I don't assign much importance to excess nutrients.  You may recall the
> fairly long discussion that Steve Dixon and I had on that topic.  The
> fact is that a lot of essential nutrients are usually in excess;
> calcium, magnesium, chloride and sulfate all come to mind.  There aren't
> many problems associated with excesses of those nutrients.

Oh Steve and I talk of little else:) Bug us both. He's helped me figure out
some interesting things over the years. He tests often enough to see tends
and most are the same as mine. What we draw from these trends, well you can
only think about some.............

>> You can't eliminate
>> algae from limiting a nutrient down super low (there is not any real
>> absence, there's almost always a trace amount that's all the algae need to
>> show themselves in tanks often, were as the plants need far more to show
>> good growth, basically you can see the algae easier in response to nutrient
>> problems). They will be the first to use any nutrient when you add more back
>> into your tank. Plants can get stunted and weak. Algae? Stunted algae? Yes
>> you can hurt it some but it's still waiting for more nutrients to be added
>> back. Then when you do and add enough so the plants are not stunted anymore
>> you start to see a reduction in algae once again. Why?
> That's my experience.  I remember that Paul Krombholz came to the same
> conclusion regarding a problem hair algae.
> I suspect that algae are disadvantaged by their relatively high energy
> demands and their susceptability to grazing.

I wonder about the energy demand. Hummm, I got to go bug someone about this
one at least to get some general ideas of certain species requirements
there. I would think that they follow population and the nutrient supply
oscillations far closer than the plants do. As a result, as they get the
food, they drop off in numbers rapidly as well as gain population when it's
restored. But that doesn't explain the nutrient limiting problem. They
should still be more limited therefore than the plants themselves. But you
can do this method when combined with herbivores and "make it work" so to
speak. But the plants would be healthier in a richer environment and less
algae would be present.
>> Roger had pointed to the plants "leaking" idea of perhaps sugars etc
>> leaching out and cause perhaps some inhibition of algae.
> Er... I don't remember saying that.  I do remember saying recently that
> I thought nutrient-limited plants would leak sugars that would *feed*
> (not inhibit) specialized algae.  That is my current best explanation
> for nuisance algae growths that appear when plants are limited by
> nutrients.

I* know it was not that but along those lines:) But it could be but don't
folks that do water changes(lots) also have similar issues? I've seen a
number of Discus folks change lots of water and try to limit. No differences
but it could be nutrients also causing the problem, masking this idea.
>> But I've done
>> serious water changes........in effort to see if removal will encourage
>> algae growth of high nutrient levels without any effects( or at least
>> minimal effects) of any plant by products. I got even less algae after I re
>> added all the nutrients then did the same water change plus nutrient rebuild
>> each time. Plants grew like mad. What's up with all that?
> If I understand what you're saying then I think that would be consistent
> with sugars leaked by the nutrient-limited plants actually feeding the
> algae.  A big water change removes the products already leaked from the
> plants and takes away the suppliment that the sugars gave to the algae.

Sounds good, I like the idea.

> Bringing the nutrient levels back immediately after the water change
> would help keep the plants from leaking more sugars into the water.

I like that too.
> Rebuilding the nutrient levels doesn't do much to help the algae since
> the algae probably never was nutrient-limited.

I like that as well.
>> Oh well it's all just a guess anyway:)
> Hopefully our guesses are getting more educated as time goes by.

Best explaination so far in my book! But it sounds multivariable and that
would make sense on why it's so hard to pin down. Differences in growth
oscillations, herbivory levels, protoza (in some cases?), water changes,
nutrient ranges and consistency, and there's more........well perhaps that
ecological modeling class will help me put all this together. Someday I
Tom Barr
> Roger Miller