4.1.2.2. Ecology and natural distribution
Artemia populations are found in about 500 natural salt lakes and man-made salterns
scattered throughout the tropical, subtropical and temperate climatic zones, along coastlines
as well as inland (Fig. 4.1.15.). This list still remains provisional as more extensive survey
work should lead to the discovery of many more Artemia biotopes in different parts of the
world (Table 4.1.1.). The distribution of Artemia is discontinuous: not all highly saline
biotopes are populated with Artemia. Although brine shrimp thrive very well in natural
seawater, they cannot migrate from one saline biotope to another via the seas, as they
depend on their physiological adaptations to high salinity to avoid predation and competition
with other filter feeders. Its physiological adaptations to high salinity provide a very efficient
ecological defense against predation, as brine shrimp possess:
• a very efficient osmoregulatory system;
• the capacity to synthesize very efficient respiratory pigments to cope with
the low O2 levels at high salinities;
• the ability to produce dormant cysts when environmental conditions endanger the
survival of the species.
Artemia therefore, is only found at salinities where its predators cannot survive (> 70 g.l-1). As
a result of extreme physiological stress and water toxicity Artemia dies off at salinities close
to NaCl saturation, i.e. 250 g.l-1 and higher.
Different geographical strains have adapted to widely fluctuating conditions with regard to
temperature (6-35°C), salinity and ionic composition of the biotope. Thalassohaline waters
are concentrated seawaters with NaCl as major salt. They make up most, if not all, of the
coastal Artemia habitats where brines are formed by evaporation of seawater in salt pans.
Other thalassohaline habitats are located inland, such as the Great Salt Lake in Utah, USA.
Athalassohaline Artemia biotopes are located inland and have an ionic composition that
differs greatly from that of natural seawater: there are sulphate waters (e.g. Chaplin Lake,
Saskatchewan, Canada), carbonate waters (e.g. Mono Lake, California, USA), and
potassium-rich waters (e.g. several lakes in Nebraska, USA).