Artificial reef modules breathe new life into waning Vaan Island, Kanimozhi pays visit

The survey also observed new coral colonies, and an increase in the spread of seagrass on Kariyasalli and Vilangusalli islands.
Artificial reef modules breathe new life into waning Vaan Island, Kanimozhi pays visit

THOOTHUKUDI: The deployment of artificial reef modules around Vaan Island has increased the land area to as much as 3.75 hectares from just 2.33 hectares in the past seven years, revealed a recent underwater biodiversity survey of the Gulf of Mannar conducted by the Suganthi Devadason Marine Research Institute (SDMRI).

The Gulf of Mannar, consisting of 21 islands, is an ecologically sensitive area stretching between Mandapam and Kanniyakumari. The islands are categorised into four, namely, Thoothukudi group (four islands), Vembar group (three islands), Keelakarai group (seven islands) and Mandapam group (seven islands). Of the 21 islands, Vilanguchalli of the Thoothukudi group and Poovarasanpatti of the Keelakarai group had got submerged as per a survey conducted in 2017.

The Vaan Island, which spanned over 20.08 hectares in 1969, broke away into two pieces in 2013 due to climatic changes, and the northern part eroded fast resulting in its submersion. A survey by SDMRI scientists at Vaan Island in 2015 alarmingly revealed that its size had reduced to just 1.53 hectares (during high tide) and 2.33 hectares (during low tide).

When the report was brought to the notice of authorities, the State government sanctioned funds under the State Coastal Zone Development Fund for deploying artificial reefs in the area through the SDMRI in order to conserve the island from further erosion. Later, the project also received funding from the Union government under the National Adaptation Fund for Climate Change (NAFCC), said sources.

Accordingly, as many as 10,600 multipurpose perforated trapezoidal artificial reef modules were laid out in a specific manner around the island by SDMRI scientists headed by Dr JK Patterson Edward in 2016. Referring to the survey conducted in August 2022, Patterson told TNIE that the island has witnessed a morphological change with the area increasing to 3.75 hectares (low tide level) from 2.33 hectares recorded in December 2015.

"The artificial reefs have helped to mitigate ill-effects of the wave energy climate, hydrodynamic conditions, and to reduce the intensity of erosion. They not only ensured the restoration of the island from further erosion but also facilitated the deposition of sediments. As many as 34 fish genera have been observed around the artificial reef modules. High densities of corals growing on them enable the artificial reef modules to behave like natural reef ecosystems," Patterson said and added that the structural complexity of the artificial reefs has made them a safe haven for the epifauna and fish, and a conducive region to find food.

The artificial reef modules become a habitat for marine life and prevent fish migration during periods of elevated temperatures and thereby helping sustenance of small-scale fisherfolk's livelihood. The survey also observed new coral colonies, and an increase in the spread of seagrass on Kariyasalli and Vilangusalli islands. The coral cover of the Gulf of Mannar suffered from a mortality rate of 16% during the 2016 bleaching event.

From 2015 to 2016, the coral areas in Kariyachalli island decreased from 44.32% to 34.01%, and from 26.78% to 19.75% on Vilanguchalli Island. However, coral rehabilitation measures have increased the live coral cover during 2016-21 from 34.01% to 41.69%, and from 19.75% to 23.70% in Kariyachalli and Vilanguchalli islands respectively.

Similarly, the rehabilitation of seagrass meadows has yielded good results as the acreage has doubled. Researchers had already noted that the Thoothukudi group of islands had experienced the highest reduction of land mass to a tune of 71% in the last 49 years due to rampant coral mining activities apart from the vagaries of climate and sea levels. Previous studies had also predicted that the Koswari and Kariyachalli islands are likely to submerge by 2036. When asked, Patterson said appropriate intervention measures like artificial reef deployment and coral rehabilitation would help save these islands from submergence and also safeguard the coast, biodiversity, and local livelihoods.

MP Kanimozhi Karunanidhi visited Vaan Island to inspect the artificial reef deployment project on Saturday. "This project by the State government has been successful in restoring Vaan Island's land area and also helped conserve coral reefs and other marine species. As the nearby islands of Koswari and Kariyachalli are also on the verge of submerging, steps will be taken to implement such artificial reef deployment projects there too," she said. Collector Dr K Senthil Raj, corporation commissioner T Charushree, mayor NP Jegan Periyasamy, district forest officer Abishek Tomar, additional collector V Saravanan and officials from NABARD were also present on the occasion.

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