Brine shrimp can be found in salt lakes and brine ponds through out the world. They thrive in extreme environmental conditions such as high salinity and temperature where predators can not survive.
Temperature thresholds are different for different strains of Artemia. In general, brine shrimp can survive in temperatures between 6° C and 40° C, with the optimum in the range of 25° C to 30° C. The dehydrated cysts tolerate a much wider temperature range, which never occurrs in nature: absolute zero (-273° C) to almost 100° C.
Brine shrimp have been found in supersaturated brines at salinities as high as 340°/oo. The lower salinity limit in which Artemia is found in nature, is in most cases a function of the presence of predators. Artemia can survive in seawater or brackish water, but have no defenses against predation. As a general rule, lower salinity limits vary from place to place depending on the upper salinity tolerance level of local predators. Salinities in Lake Abert, Oregon have been recorded exceeding 80%.
Reproduction and Growth
Brine shrimp have the ability to reproduce in two different methods depending on environmental conditions. Under favorable conditions, fertilized eggs can develop directly into free-swimming nauplii. Under extreme environmental conditions (high salinity, low oxygen levels), eggs are surrounded by a thick shell and deposited as cysts which will remain inactive as long as they are kept dry or under anaerobic conditions; they will start to develop when the salinity drops below a certain threshold. At salinities above this threshold, cysts will not hatch because they cannot hydrate enough. The salinity threshold at which cysts will hydrate is different for different strains of Artemia. When the conditions are right for hatching, within a matter of hours, the cysts hatch into nauplii which grow to adults in a few weeks.
Adult animals reach 8-10 mm long. Under optimal conditions, brine shrimp can live for several months and reproduce at a rate of up to 300 nauplii or cysts every 4 days.
Brine shrimp are filter-feeders, ingesting organic detritus and microscopic algae and bacteria. In many areas, the presence of high numbers of shrimp often coincides with blooms of microscopic algae.
Artemia can be subject to serious predation in situations where the predator can withstand the harsh environmental conditions . Numerous fish and crustacean species and some insects regularly prey on brine shrimp. One group of animals which is not so limited by the salinity barrier is birds. Artemia can be an important part of the diet of several species of waterfowl, gulls, avocets, and flamingos. The principal bird species to be the major consumers of adult brine shrimp and cysts in Lake Abert, Oregon are the Northern Shoveler and the Eared Grebe. Brine shrimp comprise 30% and 17% of their diets, respectively.