Humans benefit from a variety of ecosystem services provided by seagrass meadows. However, seagrass conservation efforts appear to be insufficient, as evidenced by its low representation in marine protected areas around the world. Protecting seagrasses benefits not just the seagrass itself, but also the macrobenthic invertebrate assemblages that dwell beside it and contribute indirectly to the various environmental services through their functions. Studies comparing seagrass-associated invertebrate assemblages and functional trait composition within and outside marine protected areas are uncommon, so the current study compares invertebrate assemblages and functional trait composition from a marine protected area (Gulf of Mannar Marine National Park) and an adjacent non-marine protected area (Palk Bay) along the southeast coast of India. The species richness (mean S = 83.3) and density (mean D = 6276.6) of seagrass-associated macromolluscs were higher in marine protected areas than in non-marine protected areas (mean S = 54.6, mean D = 5264.0), but not the species diversity (mean H’ = 2.1 for marine protected areas, mean H’ = 2.0 for non-marine protected areas). Protected seagrass ecosystems, on the other hand, exhibited much higher species richness within functional groups (i.e., deposit feeders (mean S = 5.5), micro-/macro-grazers (21.7), predators (34.8), ectoparasites (2.1) and suspension feeders (19.3)), suggesting that the protection status supports functional redundancy. The study's findings reveal the importance of protection status in enhancing macromollusc assemblages in seagrass ecosystems, which improves the ecosystem's resilience and function.

We conducted field studies to compare protected and unprotected seagrass ecosystems in a tropical setting in terms of the richness of the macrofauna that is associated with seagrass, particularly macromolluscan assemblages. Using quadrats, seagrass diversity and density were evaluated. Using modified dredge-trawl and push-net, macromolluscan diversity and density were measured and compared between protected and unprotected areas. To assess the functional species richness, abundance, and diversity between the protection status, the identified macromolluscan species were assigned to trophic categories (herbivores, carnivores, and omnivores) as well as feeding guild types (deposit feeders, micro-/macro-grazers, predators, ectoparasites and suspension feeders).