A simple closed aquatic ecosystem (CAES) for space Original Research Article

A closed aquatic ecosystem (CAES) was developed to study the effects of microgravity on the function of closed ecosystems aboard the Chinese retrieved satellite and on the spacecraft SHENZHOU-II. These systems housed a small freshwater snail (Bulinus australianus) and an autotrophic green algae (Chlorella pyrenoidosa). The results of the test on the satellite were that the concentration of algae changed little, but that the snails died during the experiments. We then sought to optimize the function of the control system, the cultural conditions and the data acquisition system and carried out an experiment on the spacecraft SHENZHOU-II. Using various sensors to monitor the CAES, real-time data regarding the operation of the CAES in microgravity was acquired. In addition, an on-board 1g centrifuge was included to identify gravity-related factors. It was found that microgravity is the major factor affecting the operation of the CAES in space. The change in biomass of the primary producer during each day in microgravity was larger than that of the control groups. The mean biomass concentration per day in the microgravity group decreased, but that of the control groups increased for several days and then leveled off. Space effects on the biomass of a primary producer may be a result of microgravity effects leading to increasing metabolic rates of the consumer combined with decreases in photosynthesis.