Bentota River mangrove oyster (Saccostrea cucullata) colonization: prop root tidal zones?

In the brackish estuary of the Bentota River (Dedduwa Lake), Hooded Rock Oysters (Saccostrea cucullata) colonize stilt roots of red mangroves (Rhizophora mucronata) in distinct vertical intertidal bands. Oysters cement their lower calcareous shell valves strictly within the mid-intertidal zone (between mean low water neaps and mean high water neaps). Submergence for at least four hours per tidal cycle allows active filter-feeding on suspended micro-plankton, while low-tide air exposure protects the oysters from subtidal predatory drills (Thais snails) and sea stars that cannot tolerate desiccation.