First approach to the characterization of the ecological succession on perforated trapezoidal multi-purpose reef modules: Building climate resilience

Abstract

The study reports the colonization and ecological succession of epibenthic communities on perforated trapezoidal Artificial Reef (AR) modules deployed in Vaan Island of Gulf of Mannar, southeast India. These AR communities assist in building climate resilience among the coastal ecosystems, which have faced severe climate change impacts during the last decade. Based on wave dynamics modeling studies, 10,600 modules were deployed in two layers to protect the Island from beach erosion and to enhance biodiversity. Randomly selected modules were subject to continuous monitoring from 2015 to 2020 to understand the ecological succession of the epibenthic communities. Hard corals turned out to be the dominant epibenthic category with 76.01 no.module−1(SE ± 2.16) by 2020. A total of 37 coral species belonging to 16 genera were found inhabiting the modules at the end of five years. The other major epibenthic categories were molluscs, hydroids, sponges, ascidians, octocorals and echinoderms with a total density of 40.44 no.module−1(SE ± 1.41) by 2020. A couple of years after the deployment, when hard corals started to flourish on the AR modules, the density of other epibenthic categories began to decline. A comparison of the numbers of epibenthic organisms on the inner and outer layers of AR modules reveals that the inner layer has a larger epibenthic community. After five years, the AR modules have started to act as coral refugia and are expected to create reef ecosystem analogous to natural reefs. The modules also provide the much needed topographic complexity for the fish to move in. This planned deployment not only helped in reef recovery and enhancement of associated biodiversity in Gulf of Mannar, which is severely impacted by global climate change, but also would serve to enhance the climate resilience of the coral ecosystems by increasing the coral biomass and thereby restoring the ecological services, which help to sustain the livelihood of the dependent small-scale fisher folk.