Mangrove ecosystem is a highly dynamic environment due to the tidal and seasonal variations of its physical and chemical properties, influencing its diversity and community structure. Six mangrove ecosystems on the southern coast of Oriental Mindoro, Philippines, were studied, and their species composition, diversity, and structural community were determined using various diversity indices and vegetation analyses. Twenty-four mangrove species were recorded which was higher compared to the previous assessment conducted in 2014. The highest species richness was recorded in Roxas (16 species), while the lowest was recorded in Bongabong (nine species). Common mangrove species in the study sites are Avicennia rumphiana, Excoecaria agallocha, Rhizophora apiculata, Rhizophora mucronata, and Sonneratia alba. Interestingly, six species are considered new records in the southern district including Acanthus ebracteatus, Acanthus volubilis, Acrostichum aureum, Acrostichum speciosum, Heritiera littoralis, and Scyphiphora hydrophyllacea. Species diversity varied per mangrove site, with Roxas having the highest diversity and Gloria having the lowest. In terms of evenness, mangrove site in Bongabong has highly proportional species abundance distribution. The most diverse mangrove ecotypes can be found in the middle and landward zones, where growth conditions are favorable. The abundance of regenerating and small stem-sized mangrove trees classified the mangrove forest communities in Gloria, Bongabong, Roxas, and Bulalacao as early growth, whereas the mangrove community structures in Bansud and Mansalay were classified as old growth, characterized by large boles and tall mangrove trees. Occasional mangrove tree cutting and fishpond activities are both regarded as potential threats to the mangrove areas. Local environmental authorities should design their own mangrove conservation framework to guide them conserve and manage their local mangroves.
