open system than can survive in the relatively poor quality closed environment. Freshwater closed systems are often attempted by nature hobbyists and as experimental projects or demonstrations for biology classes. These require nothing more than a large glass jar with an airtight lid, a few cups of lake or river water, and mud or other substrate from the same body of water. Kept indoors at room temperatures, with exposure to sunlight from a window, such systems have been found to contain living organisms even after several decades. The original level of diversity always falls drastically, sometimes exhibiting interesting patterns of population flux and extinction. Multicellular organisms fare poorly. Eventually an equilibrium of micro-organisms is established. Make magazine Volume 10 contained instructions for creating a self-contained fresh-water "biosphere", which contained a freshwater amano shrimp, snails, amphipods, ostracods, copepods, rigid hornwort, duckweed, pond scum (for microorganisms), and small rocks or shells (as a pH buffer). In their paper "The Emergence of Materially-closed-system Ecology", Joe Hanson and Clair Folsome discussed the creation of Ecosphere-like closed ecosystems. In the paper Hanson stated that the composition of the closed ecosystems he created was 50% distilled water brought to a salinity of 11 parts per thousand by the addition of "Instant Ocean", 50% air, algae collected from the ponds of Halocaridina rubra shrimp (and their associated microbial populations), and 3 to 16 Halocaridina rubra shrimp (and their associated microbial populations). No container size was given. However, in similar, 2,000 ml setups the authors noted that while the survival rate of shrimp varies it averages 4 shrimp per 2,000 ml of container when not carbon, sulfur, or phosphorus limited or 1 to 8 shrimp per 1,000 ml when limited. They also noted that the shrimp population in all ecosystems declined from the starting number to a steady state within 60 days. In the media The ecosphere was reviewed by Carl Sagan in a 1986 Parade magazine article entitled "The World That Came in the Mail". The article is reprinted as a chapter in Sagan's last book, Billions and Billions. References Ecological experiments Controlled ecological life support systems Artificial ecosystems Products introduced in 1984