Behavior of simple closed ecological systems; lower nutrient concentrations allow longer persistence of grazer populations.

We expect to develop self-sustaining extraterrestrial colonies, and they will approach being closed ecological systems. Using simple closed ecosystems containing Daphnia magna, three species of algae, and microbes, we tested multiple conditions to study long-term organism survival, which is only possible with adequate nutrient recycling. Closed and open systems behaved differently from one another at high nitrate concentrations; in closed systems, the animals were dead by day 14; in open systems, the Daphnia populations persisted beyond 273 days.

Why did carbon become the pseudo-limiting factor in aquatic closed ecological systems?

Closure from the earth's atmosphere is a critical test of an ecosystem's ability to function. In our earlier testing of autotrophic Closed Ecological Systems (CESs), a C:N ratio of 26.4 (3.

Ecosystem functions and densities of contributing functional groups respond in a different way to chemical stress.

Understanding whether and to what extent ecosystem functions respond to chemicals is a major challenge in environmental toxicology. The available data gathered by ecosystem-level experiments (micro- and mesocosms) often describe the responses of taxa densities to stress. However, whether these responses are proportional to the responses of associated ecosystem functions to stress is unclear.

Copper Dynamics and the Mechanism of Ecosystem Level Recovery in a Standardized Aquatic Microcosm.

The Standardized Aquatic Microcosm (SAM) was used to assess the effects and behavior of copper at the ecosystem level. The concentration of algal cells and Daphnia magna, pH, dissolved organic carbon (DOC), and dissolved and ionic copper concentration were measured for 489 d and used to explain the recovery sequence of a community of organisms. The results indicate that a resistant algal species was crucial for initiating the recovery sequence in these microcosms and that the timing of D.