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Re: Aquatic Plants Digest V3 #145

    This is interesting Charley. You got me thinking; what if algae were not the ones
controlling the shrimp population? What if, by making a larger environment and add
fewer consumers, the consumer population checks the algae population instead. I know,
I know; you're about to say, the population of shrimps and algae would soon reach an
equilibrium point anyway. Yeah, that's what I figured too, but still, reaching
equilibrium from an increase in the consumer population would be more stable. Would it
not?    I also go to thinking; then how does the earth balance so well? I figured that
there are extremely large numbers of producers supporting us. From countless numbers
of photosynthetic plankton to miles of forests. And all that to support just a few
weak humans who can't seem to do it right.


>
>
> ------------------------------
>
> Date: Tue, 17 Mar 1998 13:20:02 -0700
> From: Charley Bay <charleyb at cytomation_com>
> Subject: RE: self-contained ecosystem
>
> Rice writes:
> > <<  She said that these shrimps live by eating
> > > the algae that grows inside the sphere, and, in turn, the algae grows on the
> > > waste. Light is provided by normal room florescent. She also says that the
> > > shrimps live from 5-10 years and by the time they die, they will have
> > > already had many baby shrimps to replace them. I figured that the shrimp
> > > population in this sphere is checked by the amount of food they have,
> > > which is dependent on> the amount of light. >>
>
> Bob Dixon (IDMiamiBob <IDMiamiBob at aol_com>) responded:
> > With any attempt you make at this, the balance in a sealed container system
> > will find its own balance between the photosynthetic producer and the animal
> > living off it.  The trick is to figure out what species to use, and then
> > introduce only those two species.
>
> I believe Bob is right.  This "self-contained system" concept has been a
> hobby of mine for a number of years now.  The spheres in discussion
> are just as Rice describes, a sealed glass ball with algae, marine water,
> marine algae, and a small pocket (20-40%) of air.  They are the commercial
> results of research conduced by NASA and other organizations over the
> past few decades on sealed viable systems.
>
> Of course, the interest by NASA is obvious:  Determine factors for sealed
> systems so one can remain viable N-days in orbit.  The goal has been to
> increase the number "N".
>
> Olga Betts <sae at arts_ubc.ca> asked:
> > Am I wrong in thinking that this would be impossible. Surely the sphere
> > could not be completely enclosed. The living things would need air.
>
> You are correct.  These spheres must have some air, and they do,
> ranging from 20-40% air.  However, because the low oxygen demands by
> the brine shrimp, and the oxygen production potential of the algae, the
> sealed glass sphere is able to recycle the oxygen.  This fails if the sphere
> remains in the dark:  If the algae "oxygen factory" does not get light
> input, it effectively shuts down, oxygen becomes limited, and the brine
> shrimp die.  Presumably, anaerobic bacteria can then attack both the
> algae and the dead brine shrimp and you have a failed system (no restart).
>
> When these were first sold, they ranged from $40 to $120 (the larger ones
> being the most expensive).  Then, the novelty wore off and the price
> dropped.  Warranties for viability ranged from 6 months to a year, but
> nobody warranties them after a year.  I seem to recall such systems
> living as long as 6 years with good light input and temperature
> control (try to keep them from overheating).  However, they all fail
> after a period of  time with no restart.
>
> This only works at the very lowest trophic level.  Since only 10%
> of biomass actually gets converted into additional biomass at the
> next level (90% is lost to energy expenditures), and since photosynthesis
> is only about 2% efficient, it is prohibitive (today) to build any sealed
> system with any three trophic levels that lasts more than a couple
> years. Any animal with real oxygen demands makes this much more
> difficult.
>
> - --charley
> charleyb at cytomation_com
>
> ------------------------------