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Underwater Townships: Building Customised Artificial Reefs

Creating artificial reef habitats to raise and nurture life in coastal waters is an ongoing success story in the restoration of balance on various coasts across the world, notably Mexico and Japan. Closer home, the Coromandel Coast has also witnessed interesting efforts to restore ravaged marine ecosystems through the introduction of customised artificial reefs. Our contributor, Arun Vaddi, has been part of this effort, and he relays to us his experiences and learnings from the field.


The Coromandel coast on the east of the Indian peninsula stretching from Orissa through Andhra Pradesh to the southern tip of Tamil Nadu has always harboured interesting man-made and natural phenomena. A smattering of vivid colours on the earthen hues of the native land, and a myriad range of beaches, estuaries, rocky outcrops, backwater lakes, canals, mangroves, mudflats, and salt pans litter the entire stretch. The area is also whipped by cyclonic storms with unrelenting regularity. It has even seen a major Tsunami as recently as December 2004.

Smack bang in the middle of this stretch within peeping distance of the metropolitan city of Chennai lies the backwater lake of Muttukadu. Its surroundings, a microcosm of all the features mentioned above. It is flanked to the north and the west by the burgeoning city of Chennai and its IT corridor, to the east by the open ocean unhindered up to 1000kms where it hits the Andaman islands and the super seismic zone of the Indonesian archipelago, and to the south by the high seas of the Indian ocean. This variety and expanse ensure an interesting mix of aquatic flora and fauna in a variety of sizes, shapes, and colours.

A satellite map showing the village of Kovalam, Muttukadu, the Buckingham canal, and the ever-expanding IT corridor in the South of Chennai. Photograph by: Arun Vaddi


Underwater Townships and Communities

The nearshore waters are home to a number of reefs formed by natural rocks. While the shallow waters hold ornamental reef fish, breams, and others, deeper waters house pilot whales and other bigger faster fish. Dolphins cavort in both ranges in large numbers.

A diver can see big and small boulders draped in algae, whip coral, soft coral, and gorgonians, commonly known as sea fans. These corals and algae are clipped and tended by longfin bannerfish and butterflyfish, and in these gardens swim ornamental fishes like five line snappers, over 30 centimeters long sweetlips, longfin banners, Triggerfish, sweepers, surgeons, and fusiliers in tens and hundreds and thousands. On the bottom can be seen the gliding lionfish and over 60 centimeters long groupers perching on the bottom, waiting patiently for potential food. There is also a healthy population of crustaceans like crabs, mussels, oysters, shrimp, and lobsters.

A garden of gorgonians and whip coral brimming with reef fish like angelfish, butterflyfish, and breams. Photograph by: Devatva Raj

Close-up shot of a sea fan, swaying in mild currents. These make for comfortable habitats for seahorses, which cling on to the Gorgonids using their prehensile tail and catch food in the water flowing by. Photograph by: Devatva Raj


Habitat destruction has been the cause of great worry on this coast. The drop in the population of small fish has lead to the movement of bigger pelagics farther away from these coastal waters and into newer habitats. A number of fish like sharks, sailfish, marlin, tuna, and others have migrated to newer feeding grounds. This has thrown the ecology of the coastal region into disarray and the livelihoods of dependent communities are landing in a dismal state of affairs. There have been various findings and regulations that have been announced to alleviate this, but bringing them into practice has been a challenge.

Dr. Joe K Kizhakudan, Principal Scientist, CMFRI Chennai says that in the 90s, the UN, along with various organisations associated with the high seas had announced at a convention that no material that is not specifically designed and constructed for the purpose of artificial reefs will be introduced into the ocean with the intention of promoting the growth of reefs. Sadly, very few people, even those in associated areas are aware of this and continue to avoid best practices. The indiscriminate dumping of random structures and objects into the ocean in an effort to promote artificial reefs is causing unintended damage. The negative effects of leaching from submerged tyres, Ferrous compounds from items like cars and trucks and other non-galvanized iron, and chemical pollution from abandoned offshore rigs and other structures have been well researched and documented.

Under these conditions, a few projects have come shining through like a ray of hope. The torchbearer among these has been the Customised Artificial Reefs project. Creating artificial reef habitats to raise and nurture life in the coastal waters is an ongoing success story in the restoration of balance on the coromandel coast. The coastline is however forever influenced by powerful currents, winds, and weather systems. In the words of Dr. J. F. Thomas Goreau Ph.D., of Harvard University, the inventor Bio-Rock and the President of the Global Coral Reef Alliance, “The dynamics of this site is very complicated due to rainy/dry season flow variations plus waves, and it really needs to be studied very carefully by coastal engineers based on detailed site mapping.”

Of the various technologies available, research was conducted to see the best suited for these very active waters and it was found that systems like bio-rock and others were too fragile and small scale to be effective in these waters. Large stable concrete structures were then decided upon and designs were created keeping various purposes in mind. Three structures are currently in use: 

The TRIANGLE- This is a triangular tunnel-shaped concrete structure with small openings on the sides. The surface is textured and uneven to increase surface area for the development of bacteria and algae that will promote the growth of corals and other life forms. The triangular structures are very effective for ornamental reef fish like angels, butterflyfish, bannerfish, goatfish, and damsels, as well as snappers and breams.

The PIPE- This is literally a concrete pipe. The surface is finished with the same rough textured treatment. The pipe mainly supports groupers and is also known as the grouper module. Many varieties of eels also find the PIPE very conducive as their this habitat.

The RING-FLOWER- The ring flower module is an interesting one in terms of design and also plays a crucial role in the development of the reef. It is a concrete ring filled in by a flower-like motif. The nooks and crannies provide ideal spawning spaces for the fish securing the roe/eggs. They also provide safe space for juveniles, protecting them from being eaten by larger fish that find it difficult to reach into these spaces. Foraging fishes like anchovies and also shrimp and other crustaceans find this to be an ideal place.

Schools of black spot snappers, Lutjanus ehrenbergii, and yellow back fusiliers, Caesio xanthonota, over the artificial reef. Photograph by: Devatva Raj

Ring Flower Modules, waiting to be submerged under the sea. Photograph by: CMFRI

A triangular Reef Fish Module being deployed to make a home for reef fishes. Photograph by: CMFRI


About 130 such reefs have been deployed along the Coromandel coast, of which 14 are in the Kovalam-Muttukadu area. Each reef currently holds standing biomass of 25 to 30 tonnes providing a healthy resident population. This has also attracted bigger fish to return in larger numbers to these waters including some that have totally disappeared from here. Healthy plankton blooms from the artificial reefs have lured whale sharks to visit these waters. Once thought to be a rarity, they have now become regular seasonal visitors. These gentle giants make for quite a spectacular sight from boats and in the case of responsible divers, their unbelievable size and grace can be viewed from underwater. There are also the stray juvenile manta ray, a number of large stingrays, and other rays spread over this stretch.

A whale shark, Rhincodon typus, swimming right under the surface to feed on a plankton bloom nearby. Photograph by: Diksha Dikshit


The Curio Collection


The teeming aquatic life in the Muttukadu lake provides for the enormous range of resident, as well as migrant birds, which flock over these waters in hundreds. Resident spot-billed pelicans, painted storks, black-headed ibises, and cormorants grace the creeks here every dusk and dawn. Flamingos, both lesser and greater, glossy ibises, egrets, and many more migratory birds can be seen making their annual pit stops here and refueling before their journey back North.

A spot-billed pelican fishing amidst surfers at Kovalam beach. Photograph by: Bay of Life


Blue Dragon

Glaucus atlanticus, this beautiful alien-like sea slug is a gastropod mollusk nudibranch, it preys on the venomous Portuguese man-o-war jellyfish and instead of digesting its venom, it stores it in its appendages, so try not touching this beauty with bare hands. A pelagic animal that floats upside-down on the surface and travels with ocean currents.

A Dorid nudibranch gliding into a crevice in the natural reef. Photograph by: Devatva Raj


The Little Sailor

Vellala vellala or little sailor are cousins of the jellyfish. But unlike any other, they have in-built sails to help them navigate the vast oceans. They are characterised by small shimmering groups of shiny translucent sails moving with the wind on surface of the ocean.

A little blue sailor, Velella velella, a cousin of jellyfish, sailing the winds at water surface. Photograph by: Bay of Life



The Kovalam beach is a well-established Olive Ridley nesting site where a seasonal collection of eggs, their incubation, and release of hatchlings into the ocean is carried out at various points on the coast.

Evolving Realities and Rays of Hope

With the advent of mechanized fishing systems, bottom trawling, and other such practices, the small fish population has dwindled considerably. There is not enough time for this aquatic flora and fauna to rejuvenate as all stages from spawn through juveniles to adults are swept away indiscriminately. After separating commercially viable catch the by now dead bycatch is dumped back in the sea or sold for chicken feed and fertiliser.

Ghost nets carpet the reefs. Ghost nets are fishing nets that are lost or discarded into the sea. They can be found haunting the seas free-floating or entangled with reefs and rocks while killing marine life till they are physically removed. “Some of the submerged nets have aged so much,” says Diksha Dikshit, the in-house marine biologist at DIVEIndia, “that you can find coral growing on them”.

A soft coral entangled in a torn ghost net. Photograph by: Devatva RajA torpedo ray, not yet stuck in the bundle of ghost net. Photograph by: Avantika


Another bane to the existence of healthy fish life is waste and untreated sewage, which is illegally being dumped into the Buckingham canal and along its banks. The constant influx of untreated waste through the canal has affected the underwater ecosystems considerably. “You don’t find fish like sea bass and emperors at the canal mouth anymore”, states Hanif Muhammad, who has been into sport fishing in Kovalam for over 15 years now. “Once these fish used to visit these waters in plenty”, he added.

To warrant the success of these efforts, an understanding of the succession and progression of life in these artificial reefs is required. To facilitate the same DIVEIndia Conservation, with their team of marine biologists and divers, has started a long-term monitoring program, comparing old and new artificial reefs and natural reefs. They have also invested themselves in setting up reefs to supplement the existing ones as smaller auxiliary/satellite reefs.

The Bay Of Life Surf School has been working incessantly over the years on the clean-up of the beaches and water bodies and rejuvenation of mangrove and mudflat systems. They have also been training local youngsters in water sports management and training to supplement their income from fishing.

Service organisations like The Rotary Club and various citizen’s groups have now shown interest and are exploring ways of getting involved in this restoration effort of Artificial Reefs that has been showing consistent positive results. Citizen science will thus have a big role to play in the future.

The fishermen are buoyed by the success of the artificial reefs. Many villages have requested for reef system near their fishing grounds and vowed to maintain them. They have realised using less invasive and strenuous methods was giving them high-value catch.

There is constant standing biomass of 20 to 30 tonnes on each of these artificial reefs, fourteen of which are in the Kovalam area. This has resulted in a substantial increase in the income of the fishing community. What’s more, the destruction of habitat is minimal to non-existent. There is also no bycatch of any kind. While the reefs here are 250 to 300 tonne systems, the scale at which this is being done worldwide is much bigger. Off the coasts of Mexico and Japan structures of 1000 to 2000 tonnes are not uncommon. This should be possible here very soon with added interest being shown by the fisherfolk, the government, and a number of other organisations if supported by the corporate sector and aided by international funding.

Goldlined seabream, Rhabdosargus sarba, swimming over the artificial reef and Malabar groupers, Epinephelus malabaricus, waddling at the bottom near, well, Grouper Modules. Photograph by: Devatva Raj


Restoration and rehabilitation form an integral part of the conservation of habitat. Building a new habitat is a way of least invasion that can help not just in preserving populations but also in their growth. Born of this idea, these artificial reefs are a beautiful success story of man endeavouring to strike a balance between his personal needs and his responsibilities towards nurturing the environment.



This author would like to express his gratitude to the following people and institutions for their inputs:

Ms. Diksha Dikshit, Marine Biologist, DIVEindia Chennai; Dr. Joe Kizhakudan, Principal Scientist, CMFRI Chennai; Showkath Jamal, Founder, Bay Of Life Surf School; Devatva Raj, DIVEindia Chennai; Bay Of Life Foundation, Chennai; CMFRI Chennai

About the Author /

Arun is a film and theater professional, a Partner at DIVEIndia, Chairperson of Projects at ESRAG South Asia (Environmental Sustainability Rotary Action Group), as well as Proprietor, True Blue Media. He has worked extensively with citizen’s groups and government authorities on waste management and plastic mitigation in Ooty. This resulted in the ban of single-use plastic and also plastic bottles and packaging in the entire district. He has designed and executed programs to clean deep-sea ocean beds with the Coast guard, and with his own divers in the Kovalam/Muttukadu coastal region of Chennai, Tamil Nadu. He is currently working on artificial reef structures in the ocean and mitigation of waste entering the oceans near the Chennai Coastline. Arun is also an Advanced Scuba diver specialising in deep diving and night diving certified by NAUI USA (National Association of Underwater Instructors), a certified paragliding pilot, and is obsessed with Weimaraner dogs that he breeds and shows internationally.

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