Plankton communities of saline pools in a former coal mining region

We examined the plankton communities of spoil heap saline pools in a former brown coal mining area in the Czech Republic now undergoing revitalization. Together with low concentrations of total phosphorus (0.01–0.1 mg L −1 ), we recorded extremely high values for salinity (up to 13,040 mg L −1 ), conductivity (3000–16,300 μS cm −1 ), alkalinity (8.5–15.8 mmol L −1 ), sulphates (up to 15,800 mg L −1 ), sodium (2900 mg L −1 ), magnesium (910 mg L −1 ) and calcium (250 mg L −1 ) that are typical for some waters in the area. To speed up the reclamation process and improve ecosystem functioning, the pools were grouped into three categories based on the conductivity and treated using cow dung, municipal wastewater treatment sludge and inorganic NPK (nitrogen-phosphorus-potassium) fertilizer at doses recommended for carp ponds. All three fertilization approaches produced a positive impact on zooplankton density and biomass, with the greatest biomass increase recorded in pools treated with NPK and cow dung at sites with conductivity up to 5000 μS cm −1 . Zooplankton diversity was strongly dependent on pool salinity, with the halophilous rotifer Hexarthra fennica strongly dominating (> 98% of total number) in high salinity pools. Several diatom and cyanobacterial halophilic species were also found in pools of higher salinity.