henry (06/02/82)
One of the objections raised to the space-colony concept has been the total lack of understanding of how to run closed-cycle ecosystems. Attempts at creating simple closed systems that are self-sufficient in water and nutrients (not just oxygen) haven't been too successful so far. A report in the May issue of JBIS indicates that this situation has now changed. Fifteen months ago, JPL ecologist Joe Hanson prepared a number of small ecosystems consisting of one-liter flasks containing imitation seawater, assorted algae, numerous microorganisms, and inch-long tropical shrimp. The necks of the flasks were then fused shut, sealing the systems off completely from the biosphere: only light and heat get in or out. The little ecosystems are doing quite well. In a few the shrimp have died, but in most they are thriving. The algae are healthy even in the flasks with no shrimp left, suggesting that microorganisms are supplying carbon dioxide. There are other differences between various flasks; for example, different algae species are dominant in different flasks, although they all started with pretty much the same mix. The reasons for these differences are not well understood. Hanson is now trying to figure out non-invasive ways of measuring what is going on in the flasks. If this problem can be solved, these long-lived "microecosystems" may be a major breakthrough in the science of ecology, permitting controlled and repeatable experiments on whole ecosystems for the first time. The thing I find most interesting about his technique is that the stable ecosystems did not arise out of systematic planning, with a small number of species and carefully-planned interactions and cycles. I have long thought that the way to get a space colony's ecosystem going is just to transport a slice of Earth's biosphere and let it adjust to the new environment by itself.
REM@MIT-MC@sri-unix (06/03/82)
From: Robert Elton Maas <REM at MIT-MC> After the reported round-1 closed-ecosystem experiment, I suggest the following plan: Divide each of the round-1 successful systems in half, resealing one and conducting a detailed analysis on the other. The main thing to find out is whether any materials toxic to human life are abundant in the successful closed ecosystems. Throw out those which are toxic. For round-2, attempt to construct a large ecosystem containing exactly what was determined to be in each of the non-toxic successful ecosystems. Of course some tiny but necessary lifeform will be omitted, but if the first round-2 experiment with pure materials fails we can try again with a small amount of natural crud thrown in (i.e. throw in a small amount of what started the original experiment). With the system dominated by the analyzed result of the round-1 experment, but with crud thrown in to supply a seed crop of anything else needed, I expect each round-2 experiment will stabilize to exactly what the corresponding round-1 experiment did, rather than jumping to some other stable mix. This should be verifiable by comparing analysis of the round-2 results with the correspond round-1 analyses. Next, I guess we need to perform perturbation tests on the successful round-2 mixtures. See if we can add a foreign substance and have the mixture return to its original state after a while. We may find there are a finite number of stable mixtures, that adding foreign substances either returns to the same mixture or jumps to another, and we may find a recipe for jumping a mixture from any existing state to any desired state. Hopefully there's at least one stable mixture that has a high ambient level of oxygen (sufficient for human breathing) and is stable against moderate amounts of oxygen-removal algae-removal and human-waste-return. If so, we've solved the space-station problem. I hope they have funding for additional research!
steveg (06/05/82)
I suspect that you will find that ecology is a science that is not as amendable to this sort of simple minded "formula-istic" piecwise approach. - steve gutfreund