Ecospheres, Carl Sagan, and Shrimp Bisque

Ecosphere here in the science museum - colour scheme may vary

An ecosphere, seen above and below, is a sealed glass aquarium in which a self-sustaining ecosystem exists. Algae, bacteria, micro-organisms and shrimp share the space, and all that is needed for the ecosystem to survive - which it can do for a number of years - is an indirect source of light and an agreeably mild temperature. England in July would do nicely.

The ecosphere is a closed system, which by definition means energy is free to leave and enter but matter must remain confined within. While ample parallels can be drawn between this miniature system and Earth, matter can still enter our system (the Chicxulub impactor, being a modest example), and leave it (as in the estimated 300,000 pieces space junk orbiting Earth, debris which Australian scientists have their sights set on to soon start lasering).


A bit of bio-history

The ecosphere was conceived in it its simplest form in the early 1980s. Joe Hansen of NASA’s Jet Propulsion Lab and other bio-scientists discovered that, as the Ecosphere website puts it: 'diverse colonies of microbes, alga’s, and higher life forms (colonies) could persist apparently indefinitely in closed lab beakers.'

Miniature ecospheres

A succinct breakdown of the process is given on the site: 'Plants - microscopic, stringy green algae - produce oxygen through photosynthesis. The half-inch red shrimp use the oxygen and exhale carbon dioxide, the raw material of photosynthesis. Bacteria and other microscopic creatures feed on the shrimp’s wastes, converting it into fertilizer for the algae, which are eaten by the shrimp.'

Among other things, the results had implications for the possibilities of long-distance space flight. Of the initial experiments, Hanson said the beakers had 'pretty much served the purpose I had in mind...The biology community in general believed that closed ecosystems smaller than the planet probably were not possible.’ Once that point had been proven, the miniature systems were produced for museums and private collections.

'Above that, I guess, they make a bisque and not an ecosystem'

Carl Sagan, cosmologist, astronomer and sender of the Voyager Golden Records, in writing about receiving his own ecosphere through the post, was quick to highlight the elemental symbiosis of its inhabitants:

'They breathe each other’s waste gases. Their solid wastes cycle also, among plants and animals and microorganisms. In this small Eden, the inhabitants have an extremely intimate relationship.'

He writes of being enthralled by the individual trajectories and motivations of the red shrimp, and comments a little more wryly about the required ambient temperature:

'All I have to do is make sure that they’re not in too much light or too long in the dark and that they’re always at temperatures between 40 and 85 degrees Fahrenheit. (Above that, I guess, they make a bisque and not an ecosystem.)'

Carl Sagan (on Earth)

It is worth reading his article in full, but here he eloquently contrasts that world with ours:

'The shrimp’s existence is much more tenuous and precarious than that of the other beings. The algae can live without the shrimp far longer than the shrimp can live without the algae. The shrimp eat the algae (and the microorganisms), but the algae mainly eat light. Unlike an aquarium, this little world is a closed ecological system. Light gets in, but nothing else - no food, no water, no nutrients. Everything must be recycled. Just like the Earth. In our larger world, we also - plants and animals and microorganisms - live off each other, breathe and eat each other’s wastes, depend on one another. Life on our world, too, is powered by light. Light from the Sun, which passes through the clear air, is harvested by plants and powers them to combine carbon dioxide and water into carbohydrates and other foodstuffs, which in turn provide the staple diet of the animals.

Our big world is very like this little one, and we are very like the shrimp. But there is at least one major difference: Unlike the shrimp, we are able to change our environment. We can do to ourselves what a careless owner of such a crystal sphere can do to the shrimp. If we are not careful, we can heat our planet through the atmospheric greenhouse effect or cool and darken it in the aftermath of a nuclear war. With acid rain, ozone depletion, chemical pollution, radioactivity, the razing of tropical forests and a dozen other assaults on the environment, we are pushing and pulling our little world in poorly understood directions. Our purportedly advanced civilization may be changing the delicate ecological balance that has tortuously evolved over the 4-billion-year period of life on Earth.'

Sagan closes with a fairly damning, if gently worded, admonishment of our species:

'It should not be impossibly difficult. Birds - whose intelligence we tend to malign - know not to foul the nest. Shrimps with brains the size of lint know it. Algae know it. One-celled microorganisms know it. It is time for us to know it too.'

The ecosphere in the science museum in Seville is similar to those on display in exhibits in Tokyo and New York, in that the scale of the sphere (and number of shrimp) is greater than standard versions. Here in La Casa de la Ciencia, the sphere can be found tucked into the corner of a hall shared with the cetaceans of Andalucia. More about those soon...