Yala coastal lagoons (Mahaseelawa and Buthawa): summer hypersalinity and benthic diatom shifts?

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Arjun Evaporite930 rep

What seasonal evaporation rates concentrate lagoon water to 50 PSU, and how does this shift food web dynamics for wading birds and mugger crocodiles?

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Accepted Answer

The coastal villus and lagoons of Yala Block 1 (Mahaseelawa, Buthawa, and Patanangala) are separated from the Indian Ocean by tall sand dunes. During the dry season (July to September), strong southwest monsoon winds and solar heat drive daily evaporation rates exceeding 8mm. As surface water volume shrinks, salinity spikes past 50 PSU (hyper-saline, higher than open ocean water). Freshwater teleost fish die off, replaced by blooms of halo-tolerant benthic diatoms and brine flies (Ephydridae). Large flocks of Painted Storks, Spoonbills, and Spot-billed Pelicans gather to feast on trapped aquatic fauna in the shallows.

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Dr Bandara DWC1890 rep

Mugger crocodiles retreat to deep muddy wallows along the river margins or excavate 5-meter burrows into clay banks to estivate during peak hypersalinity.

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A
Arjun Evaporite930 rep

Inter-monsoon October rains breach sand spits naturally, flushing saline basins into the sea and restoring freshwater river inflow.

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Prof Gamhewage Bio1950 rep

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