Establishing mollusk colonization and assemblage patterns in planted mangrove stands of different ages in Lingayen Gulf, Philippines

We investigated the assemblage patterns and species composition of infaunal mollusks in different ages of planted mangroves (6-, 8-, 10-, 11- and 18-year old) in Lingayen Gulf, northwestern Philippines. The study aimed to determine if the mollusk assemblage was associated with the developing forest and if such patterns could provide evidence for restoration of habitat functionality. A total of 11 mollusk species were recorded. Only two species, Cerithidea cingulata (Gmelin, 1791) and Nerita polita (Linnaeus, 1758), consistently appeared in all stands where the former had increased biomass in maturing stands and the latter peaked in intermediate age stands. Vegetation structure and biomass, and sediment characteristics changed as plantations matured. Likewise, mollusk assemblages (based on species composition and biomass) significantly varied among different age stands. Such changes in assemblage patterns were correlated with vegetation and sediment characteristics. The groupings of mollusks species in the different stands can be categorized into: decreasing (species that have initially high biomass but disappeared in older stands); no detectable change (species that did not show any change in biomass); peaking (species that initially had low biomass, peaked at intermediate stands, and then diminished in mature stands; and, increasing (species that have increasing biomass with maturing stands). In summary, this study affirmed: (1) rehabilitated mangroves with increased forest structure and biomass can be effective in facilitating infaunal colonization; and (2) mollusk assemblage patterns changed as stands grow older.