Ecological peculiarities of Eurasian inland saline and alkaline soda waters

Inland permanently alkaline soda waters (ASW) are characterized by the dominance of Na⁺, HCO₃^- and/or CO₃^2-, whereas non-permanently alkaline saline waters (SW) are typically dominated by Na⁺, Cl^- and/or SO₄^2- ions. Eurasian ASW and SW constitute unique ecosystems characterized by various ecological peculiarities, where the combination of shallow water depth, intermittent hydrological cycle, high diurnal water temperature fluctuations, high inorganic turbidity, a wide salinity range, alkaline pH, high concentrations of coloured dissolved organic carbon, and hypertrophic conditions creates compound ecological extremes. The essential differences between the trophic systems of endorheic ASW and SW can be attributed to certain distinct physical and chemical properties. Among these, the higher inorganic turbidity, dissolved organic carbon, and phosphorus concentrations characteristic of ASW-in contrast to SW-are particularly prominent. Consequently, the chlorophyll-a concentrations are substantially lower than expected relative to extreme phosphorus availability results in 'phytoplankton biomass paradox phenomenon' in ASW. This paradox phenomenon can be explained by light limitation from high inorganic turbidity and relative nitrogen deficiency caused by permanent high alkalinity. In contrast, net heterotrophy and the 'zooplankton biomass paradox' also occur in both intermittent ASW and SW, driven by endorheic hydrological characteristics and abundant waterbirds populations of these waters. The simultaneously occurring dual ecosystem control (bottom-up and top-down) exerted by waterbirds is characteristic of both endorheic intermittent ASW and SW. The 'phyto- and zooplankton biomass paradox' and the dual ecosystem control of waterbirds have previously been less quantified in inland standing waters.