THE CLOSED EQUILIBRATED BIOLOGICAL AQUATIC SYSTEM - GENERAL CONCEPT AND ASPECTS OF BOTANICAL-RESEARCH

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 condition s on several successive generations of aquatic organisms. Teleost fish es and water snails in the zoological component produce CO2, ammonium ions and waste compounds which can be utilized after ammonium is oxidi sed in a microbial component by the botanical component consisting of a rootless, aquatic higher plant species which eliminates ions, i.e. n itrate, and produces oxygen for animal respiration. An electronic comp onent serves as a data-acquisition and regulation device for temperatu re and oxygen-dependent illumination of the plant chamber. A comprehen sive interdisciplinary research programme, focused around the CEBAS, i s especially well developed in the field of zoology. It covers a groun d laboratory and preparations for two scheduled spaceflight projects, as well as aspects of combined animal-plant food production modules fo r human nutrition in bioregenerative space life-support systems and fo r terrestrial production sites. In the botanical research programme, m orphological investigations on Ceratophyllum demersum L. performed wit h 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 remar kable symmetry in the arrangement of tissues was observed in stems and older leaves. The photosynthetic capacities of Ceratophyllum in the C EBAS-MINI MODULE proved to be more than sufficient for life support, a nd experiments on nitrate uptake into the plants showed their capacity to utilize ions from the water.