Continuing its efforts at conservation, the Tamil Nadu government will soon formulate a comprehensive conservation and management policy to provide the highest protection to the ecologically sensitive coral reefs and associated biodiversity and ensure sustainable livelihood to thousands of fisherfolk living close to the corals. These coral reefs are situated in the Gulf of Mannar and the Palk Bay adjacent to the four southern coastal districts of Ramanathapuram, Thoothukudi, Tirunelveli, and Kanniyakumari, encompassing a total area of 107.38 square kilometres. The predominant reef type in this region is the fringing reef. Additionally, there are smaller reef patches along the coastlines.
The marine biodiversity within the Gulf of Mannar is remarkable, with 4,223 species of marine flora and fauna, largely attributed to the extensive coral reefs. The total area of the major reefs in the gulf spans 66.28 square kilometres.
Decline in coral cover
Over the past five decades, these coral reefs have suffered a decline in health and coverage owing to a combination of climatic and anthropogenic factors. These include coral mining, which was active until 2005, overfishing, destructive fishing practices, pollution, coral bleaching, disease outbreaks, bio-invasions, space competition, and algal blooms. As a result, the live coral cover in the Gulf of Mannar decreased from 37.0% to 27.3% between 2005 and 2021, according to a study by the Department of Environment, Climate Change, and Forests and Suganthi Devadason Marine Research Institute (SDMRI).
Similarly, coral species diversity in the Palk Bay is significant, with 63 species recorded in about 20.5 square kilometres. The average coral cover, which was at 30.8% in 2007, dropped to 18.72% by 2019, primarily because of a range of climatic and non-climatic threats. A critical aspect of the Palk Bay’s reefs is their location near the mainland. Despite their ecological significance, these reefs do not receive the same level of legal protection as the reefs in the Gulf of Mannar. The absence of formal protection underscores the need for the conservation and management of the Palk Bay’s coral reef ecosystems, the study notes.
Coral reefs, comprising an array of marine flora and fauna, are critical to ecological balance as well as economic prosperity. These ecosystems are pivotal habitats, offering sustenance and shelter to numerous species of significant commercial value, including fish and shellfish. Despite occupying a mere 0.1% of the ocean floor, coral reefs are a sanctuary for approximately 25% of all known marine species. Coral reefs function as a natural defence against coastal threats such as waves, storms, and tsunamis.
Climate change
The coral reefs along the Tamil Nadu coast are primarily threatened by coral bleaching, caused by climate change. Coral bleaching occurs when the water temperature exceeds 30 degrees Celsius. This phenomenon has become an annual occurrence during the summer. While the corals recover from bleaching as the temperature drops, the events of 2010 and 2016 were exceptions, with significant coral mortalities.
Furthermore, ocean acidification, another consequence of climate change, is affecting the corals in Tamil Nadu, though the full extent of its impact remains to be quantified. These challenges underscore the urgent need for targeted conservation strategies to protect and preserve the coral reefs amid changing climatic conditions. Other threats include the growing accumulation of marine debris and derelict fishing nets in reef areas that cause a substantial mechanical damage to the corals and their associated organisms.
A threat since 2005
The invasive exotic alga, Kappaphycus alvarezii, has been a threat since 2005. Destructive fishing practices, including bottom trawling, trap fishing, and surface-supplied diving, are a significant concern as they cause a considerable mechanical damage to the corals in the Gulf of Mannar. Further threats include pollution, development activities, tourism, and pilgrimage, which contribute to the degradation of the coral ecosystems.
The Palk Bay’s coral reefs, facing similar threats, are particularly susceptible to human-induced challenges such as destructive fishing and pollution. This situation underscores the critical need for comprehensive management and protection strategies to safeguard Tamil Nadu’s coral reefs against these threats, says the study. Government-led enforcement and patrolling, coupled with awareness campaigns, provision of alternative livelihood, and community development initiatives, have been pivotal in conservation, says J.K. Patterson Edward, SDMRI director, and one of the authors of the study. Eco-development activities, sponsored by the Gulf of Mannar Biosphere Reserve Trust, have also played a significant role. These initiatives have empowered the local fishing communities, providing them with additional or alternative sources of income. Such efforts have helped to reduce the pressure on marine resources, particularly on the coral reefs, contributing significantly to their conservation and sustainability, says Jagdish S. Bakan, Wildlife Warden, Gulf of Mannar Marine National Park.
“The protection and conservation of the coral reefs in the Gulf of Mannar is a complex and challenging task as the reef areas are very close to the highly populated coast. Considering the importance of the ecosystem and prevailing climatic and non-climatic threats, the government, which has been pro-active, will formulate a policy for coral reef conservation,” says Supriya Sahu, Additional Chief Secretary, Environment, Climate Change, and Forests.
