The closed equilibrated biological aquatic system: general concept and aspects of botanical research

Abstract.

The Closed Equilibrated Biological Aquatic System (CEBAS) consists of four subcomponents which form a closed (artificial) aquatic ecosystem initially designed to study the long-term influence of space conditions on several successive generations of aquatic organisms. Teleost fishes and water snails in the zoological component produce CO₂, ammonium ions and waste compounds which can be utilized after ammonium is oxidised in a microbial component by the botanical component consisting of a rootless, aquatic higher plant species which eliminates ions, i.e. nitrate, and produces oxygen for animal respiration. An electronic component serves as a data-acquisition and regulation device for temperature and oxygen-dependent illumination of the plant chamber. A comprehensive interdisciplinary research programme, focused around the CEBAS, is especially well developed in the field of zoology. It covers a ground laboratory and preparations for two scheduled spaceflight projects, as well as aspects of combined animal-plant food production modules for human nutrition in bioregenerative space life-support systems and for terrestrial production sites. In the botanical research programme, morphological investigations on Ceratophyllum demersum L. performed with light and electron microscopy have demonstrated a gas lacuna system which, in addition to starch grains in the plastids, might regulate the buoyancy of the plant and/or serve as a `gas skeleton'. Also, a remarkable symmetry in the arrangement of tissues was observed in stems and older leaves. The photosynthetic capacities of Ceratophyllum in the CEBAS-MINI MODULE proved to be more than sufficient for life support, and experiments on nitrate uptake into the plants showed their capaCity to utilize ions from the water.