Arid and Semi-Arid Saline Lake

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The aquatic communities of saline lakes are comprised of a diverse range of biota  including archaeobacteria or halobacteria, eubacteria, cyano bacteria, algae, macrophyte (aquatic plant), crustaceans, insects, non-arthropod invertebrates and vertebrates including fish and birds. The aquatic ecology of saline lakes is primarily influenced by the interaction of three main drivers: salinity levels, frequency of inundation and nutrient loads.

Salinity levels: The composition of biological communities in salt lakes is different from that in freshwaters with differences in composition becoming more pronounced as salinity increases. As a general rule, both species richness and diversity in inland saline waters decreases with increasing salinity. The relationship between salinity and species richness is particularly clear at the upper end of the salinity spectrum. The number of species is greatest in subsaline waters, decreases dramatically at low salinities, and then continues to decrease gradually with increasing salinity. However, as a determinant of community structure, salinity levels appear to have minimal impact in highly saline systems and is of greatest importance when salinities are less than approximately 50 g/L. In hyposaline waters (between 3 and 20 g/L), most taxa present, at all taxonomic levels, are also found in freshwaters. The biota essentially comprises halotolerant freshwater forms. In mesosaline waters, (between 20 and 50 g/L), there are few halotolerant freshwater taxa and most of the biota comprises taxa restricted to inland saline waters of moderate salinity. In hypersaline waters (greater than 50 g/L), the biota is almost entirely restricted to highly saline waters with only a few genera and even fewer species also found in less saline waters. Since salinity often exceeds 50 g/L (up to 350 g/L and beyond in certain lakes), throughout most of the range of salinity in salt lakes, the biota of salt lakes is quite different from that of freshwaters.

Frequency of inundation: The frequency of inundation is important in determining species composition with occurrence patterns varying between commonly wet, intermittent (water is present on a seasonal basis) and episodic (water is present only after unpredictable rainfall events) saline lakes.

Nutrient levels: In combination with salinity and inundation regimes, nutrient levels are important in determining the dominant form of primary production, which in turn is an important driver of diversity and abundance patterns of the aquatic fauna.