Context

The National Centre for Coastal Research’s (NCCR) proposal of dropping ‘melted plastic rocks or slabs’ on the seabed for growing coral reefs and address the problem of disposal of plastic waste has drawn criticism from the Gulf of Mannar (GoM) Marine National Park, which has been implementing coral rehabilitation programme since 2002.

About

• Coral reefs and seagrasses are important for biodiversity and livelihood but they are fast degrading owing to climatic and non-climatic factors.
• The impacts of climate change since 1998 and the effects of non-climatic factors, mainly destructive fishing practices, mining, pollution, and coastal development, have altered the community structure and health of corals and seagrasses. Lowtech and low-cost transplantation techniques have been successfully standardized and implemented in the Gulf of Mannar, southeast India.
• A coral rehabilitation technique, perfected in 2002, comprising selection of site, identification of suitable native species, precision in fragmentation, choosing fragment size, fixing positions, and effective monitoring protocols, resulted in good growth and a survival of 80.1%.

The Gulf of Mannar Marine National Park:

• The Gulf of Mannar (GoM) on the southeast coast of India is one of the four major coral reef areas in India with 117 corals species
• The coral reefs in GoM are formed primarily around the 21 uninhabited coral islands that occur between Rameswaram and Tuticorin.
• This area was declared as Gulf of Mannar Marine National Park by the Government of Tamil Nadu in 1986.
• For management purposes, the 21 islands of GoM have been put under three groups: Tuticorin group, Keelakarai group, and Mandapam group.
• GoM was once considered a biological paradise, but various human activities have put the ecosystem under stress with several biological resources dwindling. Coral mining, destructive fishing methods, climate change, and pollution have caused severe damage to the ecosystems of coral reef and seagrass.
• Massive corals were also used for the construction of building and roads during the 1960s.

Kariyachalli and Vaan islands in Gulf of Mannar:

• The Gulf of Mannar Marine National Park has proposed to cover one sq km of area in Kariyachalli and Vaan islands in Thoothukudi group in Gulf of Mannar for rehabilitation of coral reefs.
• Vaan is one of the 21 islands in the Gulf of Mannar, which was declared a marine biodiversity park in 1986.
• The GoM Marine National Park had been implementing the corral rehabilitation programme since 2002 and had so far covered eight sq km areas in GoM region, where coral reefs suffered bleaching and degradation due to climate change and high temperature.
• The rehabilitation programme, employing ‘concrete frame slabs’ method, would be launched after getting government approval.
• As the sea would be rough during the southwest monsoon season, they would commence the insertion of slabs after the end of the season.
• Proposal to drop around 200 concrete frames, tied with live corals around the two islands, where coral reef degradation and bleaching were noticed.
• Corals would start growing in 60 days using the concrete frames as sub-state. The acropora coral species would grow by 10 to 12 cm per year.

Why criticism?

• Suggestion from NCCR came that plastic waste materials could simply be wound around as hard substrates as a way of disposing of them and help build coral colonies.
• With International examples such as use of Worn out tyres were tried as artificial reefs in Florida and Costa Rica, but they turned out to be catastrophic.
• NCCR’s idea would turn the reefs into graveyards as Corals in the GoM are already stressed and bleached under climate change
• The structures might look useful initially, but would destroy corals lately.

Tamil Nadu deploying artificial reefs to save sinking islands:

• Sinking islands may become a reality with sea level rise and climate change in decades to come. Tamil Nadu has hit upon a novel idea to protect such islands on its coast—deploying artificial reefs near vulnerable islands.
• Artificial reefs, made of concrete, have been found capable of preventing further erosion of ecologically sensitive islands and regenerating coral biodiversity in the Gulf of Mannar.
• It is the first attempt in India to protect and restore a sinking island. Deployment of artificial reefs parallel to the sinking island in the seaward side reduces the effect of currents and waves, enhances fish habitats for higher fish production and protection of fish diversity.
• Natural corals get attached to artificial reefs over time and start regeneration.
• Following the success in Vaan, Tamil Nadu has proposed to undertake restoration of two more islands and has approached Green Climate Fund for funding of Rs 100 crore.

Concrete slab frame construction: A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel-reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving