Prashant, ShreyasGhanekar, ChinmayaDutta, SutirthaJohnson, J.A.2026-07-292026https://digitalrepository.wii.gov.in/handle/123456789/1453Rocky intertidal ecosystems have long served as natural laboratories for testing fundamental ecological theories. However, much of our understanding of community assemblages in these systems comes from temperate shores. In contrast, tropical intertidal ecosystems remain largely understudied. The disparity in environmental conditions between the temperate and the tropical zones limits our understanding of ecological processes. Therefore, investigating how environmental and biotic factors drive tropical community assemblages is critical for assessing the generalizability of existing ecological theory. This study examines the effects of environmental stress gradients ranging from the upper to the lower intertidal zones on community and functional assemblages in Goa’s rocky intertidal ecosystem. The influence of predation on community composition is also investigated within this ecosystem. To understand the effects of the environmental stress gradient and multiple fine-scale habitat characteristics on the community, a transect-quadrat method was employed across three study sites. The environmental stress gradient was found to be the main factor influencing community composition and structure, while sand cover, wave action and substrate complexity operated at finer scales within the broader gradient. Functional traits were compiled for the organisms found within the quadrats. This trait matrix was then used to assess whether motile and sessile animals respond differently to gradients of environmental stress and algae cover. Motile animals showed functional dispersion along the biotic gradient, while sessile animals showed a functional trait shift along the stress gradient. This suggests that motile animals may respond through biotic facilitation, driven by the combined effects of decreased stress and increased algal cover. Lastly, predator-exclusion cages were deployed to investigate whether predators considerably affect community composition. The experiment used Indothais blanfordi, a predatory sea snail, as the focal predator of Brachidontes mussels. Indothais had a strong effect on both Brachidontes mussels and community composition. Together, the results show that the environmental stress gradient structured the community through environmental filtering. However, the mechanisms through which this occurs are nuanced and depend on organismal life histories, biotic interactions and fine-scale habitat mediators. These findings extend environmental stress gradients and environmental filtering theory, developed primarily along temperate shores, into an understudied tropical system. In doing so, it provides an ecological foundation and methodological framework from which further questions can now be pursued.enIntertidal ecosystemEnvironmental stress gradientSpecies assemblageEffect of environmental stressCommunity structureThesis