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Re: Algae:plant competition and carbon

Roger Miller wrote:

> I checked a couple sources and came up with (all in weight ratios):
> 
> C:N:P in aquatic plants (from Walstad, based on 40% carbon)
> 285:   11:1

True aquatics or all the common ones like swords/amphibious plants included
as well?
Both true aquatics and macro algae have more space between adjacent cell
walls to provide flexibility (There are exceptions on both sides but
generally speaking). If they did not have this they would break easily. Many
plants will break. Kelps are like rubber. They also do not have to deal with
so much gravitational & desiccation issues. Some intertidal algae do.

These amphibious plants have more cell wall/structural/cuticle and less
space in between the cells adjacent to each other. This makes them more
rigid along with secondary cell wall thickenings etc. This C source adds up.

> 
> Data from Raven:
> C:N:P in phytoplankton
> 75: 9-11:1  (Chlorella)
> 49: 5- 9:1  (Euglena)

These need no support relative to the larger plants, therefore less
cellulose(carbohydrates) and less carbon by weight.
> 
> C:N:P in freshwater macroalgae
> 117: 6- 8:1  (Nitella)
> 174:   17:1  (Hydrodictyon)

These are some of the more representative groups of algae in our tanks but
the Nitella is more plant like and the Hydrodictyon (soccer ball algae) is
more like more common hair algae perhaps. Pretty close (117) to the 106
phyto's. I'd imagine Oedogonium, BBA and others are not to far off.
Cladophora has more.
 
> 
> C:N:P in marine macroalgae
> 106: 3- 4:1  (Macrocystis)
> 600:25-50:1  (Laminaria)

That doesn't match with what I was told by the professor. I will double
check with him on that one. Perhaps he switched the Laminaria around.
That's seems too low for the Macrocystis though. How can the average phyto's
be the same as something as large and specialized as Macrocystis? I'll look
into it but it doesn't seem right. There's a Raven book around here
somewhere.
> 
> There's a huge variation in these values, and there was some data
> processing involved but the trend is fairly clear.  Larger algaes have
> more carbon relative to N and P than do smaller algaes.  Plants are
> higher yet.  The Laminaria analysis is odd.  The P content is very low,
> giving very high N:P and C:P values, but pretty normal C:N ratios.

Algae is odd to begin with:) Compare Ulva to Codium.
> 
> In discussing variations among the algae, Raven suggested a correlation
> between the high C content of the larger algaes to the presence of a
> thicker cell wall.

This is my main sticking point on this as well.
> 
> Where are our typical nuisance algae relative to the types shown here?
> Green water is phytoplankton, so that's fairly clear.  Diatoms aren't
> addressed.  My guess is that our tough, attached and filamentous algaes
> have thick cells walls and are more similar to the macroalgaes than they
> are to the phytoplankton.  Either way, carbon would still be higher in
> plants than in algae.

The cell walls in the samples I've looked are thicker in some species such
as Cladophora and Nitella, Chara. These are also more plant like(higher)
algae. They aren't particularly difficult to deal with.
 But the other problem algae tends to be smaller.
> 
> Certainly it seems possible that carbon could limit plant growth in
> cases where it doesn't limit algae growth.  On the other hand, there are
> so many other variables involved that I don't think the compositional
> analysis alone provides a very strong argument.

Certainly as the plant and algae growth is multi factorial. But it does show
that in order for each to grow, that a much larger % of Carbon is needed for
the plants relative to the algae that cause us problems per unit of energy
expended.
> 
> Interestingly (to me, anyway) Raven pointed out differences in the
> concentration of electrolytes (K, Ca, Mg) between different algae and
> related those to the volume of vacuoles in the cells.  It would be
> interesting to see how that variation carried over into aquatic plants.

Some are plain weird and make no sense. Some kelps concentrate carbon
monoxide in the pneumatiphores up to over 10% in some samples. There's
certainly far less known about algae physiology than plants. So much is just
not known. Few folks go into algae. But plants like algae concentrate some
solutes for no good obvious reason and some are poisonous/toxic.

Regarding concentrations of internal masses % etc: algae and plants
concentrate things once they get it. Even if the level of N:P:C are low in
the surrounding waters. It is not automatically reflective to more C but it
certainly seems to be  helpful for less energy usage to carry out these
concentrating processes in plants relative to algae. C can become limiting
for plants much easier than for algae based on mass ratios alone. Nothing
too new here but something to consider.
Regards, 
Tom Barr