Biosphere Jar

I have embarked on a project to create a self-sustaining (almost) ecosystem in a jar which will reside in my biology 11 classroom as a collection of live specimens alongside the numerous preserved specimens already on display in the room. The jar itself is glass and holds approximately two litres of water when full. The inhabitants of this "biosphere" in a jar are a shrimp (Neocaridina heteropoda), a Java moss plant (Taxiphyllum barbeiri), algae, various species of beneficial nitrifying bacteria, and other microorganisms. The concept behind this biosphere is that the nitrifying bacteria convert ammonia into nitrite and then nitrite into nitrate. The plant photosynthesises from light coming through the jar's glass, absorbs carbon dioxide and excretes oxygen, and takes in fertiliser in the form of nitrate. The shrimp eats algae and microorganisms growing on and off of the plant, breathes in oxygen and breathes out carbon dioxide, and excretes waste that break down to form ammonia. The algae fulfills the same role as the plant (except it is eaten by the shrimp). Because of this interdependent food web, this biosphere requires no outside input except light to maintain life inside itself.

This biosphere, however, is not a perfect ecosystem. Because the shrimp does not actually eat the plant, the plant will eventually need trimming back in order to prevent it from taking up too much space in the jar. Also, I determined that the light in the classroom was not supplying the biosphere with enough thermal energy, and so the jar is now placed atop a small raised pane of glass with a heating pad attached to its underside. My homemade biosphere was officially sealed on 5 November 2010. It will reside in my biology classroom for the rest of the school year.