Record of Coral-Associated Benthic Fauna Recruitment on the Biorock Reef Structures at the Reef Restoration Sites in the Gulf of Kachchh

Biorock technology is one of the latest coral reef restoration methods worldwide. This method induces the growth of calcareous marine organisms on a metal frame substratum supplemented by a small voltage of electric power. In addition, mineral accretion also occurs on the frame. The mineral-accreted structure acts as a calcified reef and attracts numerous coral reef-associated benthic fauna to thrive on the structure, thereby creating an ideal coral reef ecosystem. In the present study, to understand how bio-rock structures rapidly establish as functional reefs, the recruitment of coral reef sessile benthos and coral-associated organisms was assessed on the two bio-rock structures deployed in Mithapur and Arambhada sites in the Gulf of Kachchh. The assessment involved identifying the organisms in situ (confirming the identity with the support of macro photographs) and enumerating their abundance. The results showed that among the non-motile organisms, the highest recruitment was observed in ascidians, with 22.7% at Mithapur and 21.5% at Arambhada. Sponges, bryozoans, and hydrozoans showed the lowest percentages. Among the motile associates, molluscs exhibited high abundance, with 97.9% at Mithapur and 95.7% at Arambhada. Other groups recorded include arthropods, annelids, and Platyhelminthes. Among other life forms, crustose coralline algae (CCA) exhibited overall high recruitment, with 23.7% at Mithapur and 24.3% at Arambhada structures, enabling favourable conditions for coral larvae settlement. The seasonal trend showed the winter months favouring the highest recruitment, with reduced numbers in the post-monsoon and summer. During the monsoon season, increased water currents, bringing highly turbulent waters restricted the establishment of these associates. Mitigating steps such as removing turf and fleshy algal overgrowth and cleaning sediment deposition to favour the recruitment of associates during the monsoon season were proven successful. Continuous monitoring is required to assess the long-term effects of these interventions and to optimize strategies for reef restoration and resilience.