Slippery sailors of the sea: India’s Sea snakes

In Indian mythology, Vishnu, the Lord of preservation, is said to have been supported by a giant sea snake called Shesha that rests on the cosmic ocean upon which the entire world is balanced. Snake Vasuki was wielded as a rope to churn milk from the ocean. Our myths, legends and stories have always integrated sea snakes and serpents into their storylines. Whether these stories have portrayed them as holy, higher entities or as ruthless monsters, they have familiarized the idea of sea snakes in us since our childhood. Out of the 3000 species of sea snakes found across the globe, India is endemic to 26 species according to a report catalogued by Chennai’s National Centre for Sustainable Coastal Management (NCSM).

Herpetologist Nirmal Kulkarni says that all snakes can swim. “In fact, all snakes are good swimmers and have to drink water in order to survive. Water snakes are a common grouping of snakes that are found in the vicinity of water bodies.” But land snakes and sea snakes are distinctly different from each other in their physiology, adaptations and behaviour. Sea snakes, which are largely venomous creatures that fall in the Elapidae or cobra family, have a flatter body than land snakes and own rudder-shaped tails that facilitate them in sifting through their marine ecosystem. Eyes and nostrils are situated at the top of their heads for most sea snakes. As air-breathing creatures, these features aid them in breathing with only the tip of their head peeking above the surface of the water. Although some of these slithering monsters could grow as long as 2.7 metres, most adults attain a length of 1–1.5 metres during their lifetime.

Sea snakes are categorized into two basic kinds. True sea snakes, which are labelled under the genus Hydrophis, are the ones that live their whole life exclusively in the sea. The other variety called sea kraits is segregated into the genus Laticauda and consists of snakes that favour plodding in estuaries, mangrove swamps, coral reefs and mud flats rather than in the nearby water body itself. 52 of the total sea snake species are identified as true sea snakes.

Sea snakes are predominantly found in the tropical and sub-tropical coastal regions of the Indian and Pacific oceans. The hook-nosed sea snake (Hydrophis schistosa) is the most prevalently found species in India. They are distributed across a range of deep and shallow waters. Also known as Beaked sea snakes, these are lethally venomous creatures who rely on their toxins to catch their prey instantaneously in the aquatic ecosystem. They possess a beak-like or hook-like rostral scale that protrudes above their mouth. They are usually known to prefer sea catfishes, eel-tailed catfishes and pufferfishes. Annulated sea snake (H. cyanocinctus), which has unique triangular stripes over a cream coloured body, and the many-toothed Malacca sea snake (H. caerulescens) are two other types in the Hydrophis genus or true sea snakes that are native to India.

The Rainbow Water Snakes (Enhydris enhydris) are largely freshwater snakes that pervade settings like marshlands, ponds, rice paddies etc. Two long, pale stripes run down the length of its body and intersect on the crown.

In the other category of Sea Kraits in the Laticuda genus, India is home to Banded Sea Krait (Laticauda colubrina) and Blue Lipped Sea Krait (Laticuda laticaudata). The Banded Sea Krait also referred to as yellow lipped sea krait, are nocturnal species that contain alternating markings of black with blue, white or grey rings. They also have a prominent yellow snout, thus the name Yellow lipped sea krait. These snakes crawl up into limestone caves and rock crevices to lay their eggs. The Blue Lipped Sea Krait or Blue-ringed sea krait is the reptile replica of the blue-black version of “Is the dress blue-and-black or gold-and-white?” It is found in abundance on the coasts of the Bay of Bengal.

Some other sea snakes that traverse the oceans of the Indian Ocean are Annandale’s Sea Snake (Kolpophis annadalia) and Shaw’s Sea Snake (Lapemis curtus). From Genus Rhabdops, species like Rhabdops olivaceus and the Rhabdops aquaticus populate the streams of West Bengal.

However, the continuity of these sea snakes is threatened by climate change, excessive fishing and increased human intervention. Sea snakes are found as bycatch in fishing nets and are often killed or left to die by the fishermen. Although these snakes are protected under schedule IV of the Indian Wildlife (Protection) Act, 1972, they are of no economic value to the fishermen, and that lands as a huge disadvantage to the sea snake population. A significant incident of Mass bycatch would be the one in Goa where 81 hook-nosed sea snakes were found dead over an expanse of beach shore as small as 30 meters. Tragically, the same woe repeated itself only a couple days ago with 69 dead hook-nosed sea snakes. We could prevent such incidents by directing more incentives to sea snake monitoring and research, more funds into constructing safer fishing gear etc.


  1. Distribution of Sea Snakes in the Indian Coastal Waters by P. Kannan and M. Rajagopalan
  2. Sea snakes –
  4. Threatened and undocumented sea snakes of India – Mongabay news

Through the ordeals of an island: How to survive when you’re stuck on an island by India’s coastline

From literary classics like Lord of the Flies to films like Castaway and Blue Lagoon, the “stranded at an uninhabited island” trope is extremely pervasive in the realm of fiction. The trope is so familiar that it even earned a name to it; Robinsonade. A Robinsonade is a storyline that follows one or more characters who are marooned in the wilderness due to unanticipated causes and are left to claw and scrape from what nature has to offer. However, surviving on an island post a shipwreck in real life could be harder and more dangerous than the romantic renditions that films have fed us. So how do you survive when you’re stuck in a land with only endless stretches of ocean to look at. It might be a physically and emotionally crippling process that could sway one’s judgment easily.

Therefore, the first tip that one must try their best to follow is to keep calm. Help might be on its way already, so keeping cool and not panicking will best help conserve your energy. Gather as many essentials as you could from the ship and quickly swim away (preferably breaststroke) from the shipwreck, since the sinking ship might cause suction and pull you into the water. It is always advised to be prepared with a set of requirements beforehand, like flares, a first aid kit, flashlights, batteries, mirrors to reflect on surfaces, magnifying glasses, a matchbox, drinking water, canned food etc. Carefully look for injuries on your body since an infection that isn’t nursed properly or a blood clot may reduce the odds of your survival drastically at a later stage. Former Navy Lieutenant commander Paul Hart said that the first essential you should rummage for after wreckage is ‘rubber boots’ to protect your feet.

Shelter, food and fire should be your biggest priorities if you’re abandoned on an island.

A good and safe shelter is essential to protect you from exposure to the harsh climate and predatory animals that might be around. A shelter can play a big role in saving you from a heat stroke if the weather is extremely hot, or from hypothermia if the weather is unbearably cold. Bamboo stems and palm fronds must be abundantly available in the tropical islands around the Indian coastline. Bamboo, being one of the strongest woods available, is an ideal foundation to hold up your shelter. Firmly fix a few large bamboo stems into the ground and top them with dried palm fronds, which will act as the roof.

Your chances of survival are ten folds higher if you find a freshwater source near you. A study based on modern-day hunger strikes proposes that an average human can conveniently survive without proper food sustenance for as long as two months. Yet, it takes less than 8 days without water to take down a person. Dehydration leads the cells of our body to shrink and severely impedes blood circulation, oxygen circulation and most other essential body functions for survival.

Possible sources of freshwater around you are island rivers, lakes, ponds, caves etc. Water usually collects in valleys, so moving downhill spikes up your odds of finding a waterbody. Pay attention to the direction in which animals are moving by following footprints on the ground and to which way birds are flocking towards. Plush greenery is also a good indicator that there’s a water body nearby. Lend your ears to nature while you’re resting, because you might be able to hear a stream or river running nearby. It’s strictly advised not to consume saltwater directly from the ocean, especially since the salt might cause dehydration. If it rains on the island you’re stranded on, you can also conserve rainwater in a pit. Coconut water is a ready source of water and nutrition (like potassium, vitamin C and carbohydrates) on a tropical island. Be sure to not shake the tree from the bottom to acquire the coconuts since the chances of the fruit falling on you is fatally high. Carefully climb up the tree and pluck them. Most tropical islands around the Indian coastline will house a dense growth of flora and fauna. You can feed on berries, fruits and nuts while you hunt for small animals or fish.

The crucial thing to do after finding water is to purify it. Although you might be deceived by how clean a river might look, it could be wallowing with a range of harmful bacteria and viruses. Boiling is the best way to kill microorganisms. You could break a bamboo stem and use it as a water bottle or store water in the shells of fruits or nuts. Feel free to improvise with what resources you can find around you. Carving tools out of sticks and branches could come in handy when you need a spear to catch fish, snails or crabs to eat. It’s best to avoid jellyfish, fish that have spikes or puff up. Now it’s time to build a fire, and roast some fish and moon-gaze in the dark.

The most pivotal essential, while you’re stuck on an island, is fire. It’s going to be the key source of warmth and will help repel predatory animals and insects. Collect as much wood as possible and slowly build a fire. Anything from tree barks to coir can fuel the fire, given that they’re completely dry. It’s a bonus if you began a fire on flat and dry ground close to a firewood source.

In William Golding’s Lord of the Flies, Peggy lights a fire by focusing the sun with her spectacles. This eventually became the crucial plot point that helped the stranded boys to be rescued. Fire could also save the day by catching the attention of a ship or plane that might pass the island.


  1. wikiHow – How to survive after a shipwreck
  3. – Castaways: Seven incredible stories of human survival
  4. HowStuffWorks – How to survive a shipwreck
  5. Lord of the Flies – William Golding

The Fall of the Coral Reef: Lakshadweep

Situated about 200 to 440 kilometres off the Malabar Coast, Lakshadweep is an archipelago of 36 islands in the Arabian Sea, of which 10 are inhabited. All of India’s coral reefs are Fringing reefs, except for Lakshadweep, which houses a breathtaking boundary of atoll reefs. An atoll is a ring-shaped coral reef that partially or entirely loops around a lagoon. This feature makes Lakshadweep a unique destination to check off one’s bucket list. This cherished uni-district Union Territory of India houses 12 atolls, three reefs and five submerged banks. Tourist brochures allude to its scenic beauty and the multitude of activities it offers like scuba diving at Kalpeni Island or Snorkeling at Agatti Island while advertising Lakshadweep.

Lakshadweep is a dwelling ground for a large body of diverse flora and fauna. With several species of seaweeds and seagrasses, mangroves, molluscs, marine fishes, corals, and economically and ecologically crucial species like tuna, dolphins, whales, marine turtles and sharks, the colourful Lakshadweep is a melting pot of endemic wealth. Corals constitute a major part of the island’s ecosystem and play a crucial role in controlling the conditions of the island.

Coral reefs are soft-bodied underwater ecological communities with colonies of coral polyps bound together by calcium carbonate that deposit over them with time. Although mistook as plants, corals very much fall under the category of Animalia. However, being an incredible sight for sore eyes isn’t their only purpose. As humongous, breathing systems, corals have the capacity to control global warming to a substantial level by regulating carbon dioxide in the ocean. Since corals also catalyze seagrass growth, they help form a stable seabed as a consequence. Corals, along with their surrounding biodiversity, also aid in purifying the water. Researcher R.M. Hidayathulla remarks that “The corals of Lakshadweep are the lifeblood of the islands.” They especially sustain a diverse range of marine organisms in their immediate habitat, and the deterioration of coral health is bound to affect the quality of life for these organisms and vice versa. 

The six species of seagrasses named in the islands of Lakshadweep, which include Thalassia hemprichii and Cymodocae rotundata, significantly help in fending off erosion of the beaches. The indigenous green turtles of Lakshadweep majorly feed on Thalassia hemprichii. This example is indicative of how codependent these species are on each other.

The practice of coral mining is increasingly becoming a prevalent plague in Lakshadweep. As a cheaper and abundantly available alternative to cement, the corals are predominantly used for construction activities like building roads, houses, seawalls etc. Seagrasses and weeds are predisposed to decrease when the coral numbers dwindle, therefore accelerating the erosion of seabeds. This is a major threat to the islands as it could eventually lead to the submergence of the entire island.

Other anthropogenic activities in and around coral islands like excessive fishing, poaching, lagoon dredging, and urbanization in the immediate environment of the corals also cause a threat to their existence.

However, the biggest evil looming over the islands of Lakshadweep is global warming. Increasing temperatures of seawater are not only perilous for the coral reef, but also to the entire island ecosystem. A report laid forth by the Intergovernmental Panel on Climate Change predicts that our coral reefs could undergo a mass die-off by the year 2040.

Due to increased seawater temperature, coral bleaching has become a new nightmare. The corals accommodate algae over them, with which they have a symbiotic relationship. The corals provide the algae with a home to thrive in and photosynthesize, while the algae provide nourishment to the corals. It is these algae that decorate the corals with a hue of colours.

Although the aesthetic value of the corals is the pivotal factor for Lakshadweep being a key tourist destination, the quality and health of the corals have also slowly begun trickling into the tourist discourse. One tourism agency even advertises Kadmat Island as an “Unspoiled coral mine and marine reserve” to better appeal to the public.


  1. Marine Biodiversity of Lakshadweep: An overview Basudev Tripathy
  2. Lakshadweep island – Wikipedia
  3. Excessive mining leads to declining coral reefs in Lakshadweep – The Hindu
  4. The Great Coral Grief of Lakshadweep islands by Sweta Daga –
  5. The dying corals of Lakshadweep –

The Clean for the Olive Green and Blue

Since time immemorial, Chennai’s coast has proved to be an important aspect of the city. Playing several roles such from a busy harbour, to a site of leisure and fun, life without a beach in Chennai is quite difficult to imagine! The coast is bound by the Bay of Bengal, making it an important marine ecosystem. A large variety of flora and fauna can be found along the coast of Chennai that is said to have existed for thousands of years. 

Over the last few decades, however, this ecosystem has been rapidly declining due to an uncontrolled amount of anthropogenic (environmental change caused or influenced by people, either directly or indirectly) activities along the coast. The coast that was once famous for the nesting of Olive Ridley Sea Turtles had become a site for food stalls and social activities, increasing the usage and dumping of plastic and other waste in our beach. 

Every year, between January and May, thousands of Olive Ridley Sea Turtles can be spotted on Chennai’s beaches as they make their way to lay their eggs on the very beach where they were born in! That’s what makes this coastline so beautiful. In an effort to conserve and protect this fragile ecosystem, E.F.I hosted voluntary beach cleanups over the weekends to spread awareness and clean our beaches. Take a look at the cleanups conducted so far!

The Mega Beach Clean up of January 2022

The heavy rains from the North-East Monsoons of 2021 filled up the lakes and ponds in Chennai. Somewhere else, things were not the same. Our beaches. Tonnes of waste from the city got spewed into the sea. On a fine winter Sunday morning, with a cool gush of air that had blown past us, with gloves tightened, and with sack bags in hands, our volunteers were ready to pick up non-biodegradable waste from Chennai’s fragile coast. Our day started with the collection of trash from 10 different locations in South Chennai. Locations are given below: 

  1.     Broken bridge to Olcott Kuppam stretch 
  2.     Ashtalakshmi beach
  3.     Arupadai veedu beach
  4.     4th Seaward road, Thiruvanmiyur
  5.     Palavakkam beach
  6.     Neelankarai beach
  7.     Olive beach (Injambakkam)
  8.     Injambakkam beach
  9.     Akkarai
  10.     Panaiyur     

   Beach clean up summary:

S. noLocationNo of VolunteersNo of sack bags collectedTotal amount of Garbage
1Broken bridge2401301560
2Ashtalakshmi beach1401101320
3Arupadai veedu  beach4020240
44th Seaward beach7060720
7Olive beach9460720
912 volunteers540 sack bags6468 kgs of garbage

Fabulous February

Over 250 volunteers united to stand against pollution on Sundays and emerged victorious at 3 beaches, the Ashtalakshmi Temple beach, 4th Seaward Beach and the Neelankarai Beach. Close to 2.2 tonnes of plastic and other waste were removed from these beach stretches!

The Oh-So-Blue March

The ‘Water’ month as we like to call it never ceases to amaze us. Over 6 massive cleanups were conducted along the coast, hosting over 623 volunteers as the heat began to seer on. But the summer heat didn’t stop our beach warriors! Close 6.5 tonnes of waste were removed from our beaches during this month!

April and the upcoming months

We’ve so far been able to conduct activities every weekend and will be continuing to do so in the upcoming months! We invite you to join us in this effort to clean for olive green and the blue.

For regular updates, follow us on our social profiles!

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Volunteer for India and her Environment with E.F.I

Common Bivalves in Chennai

by Goutham Krishna

Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia

Bivalves are marine or freshwater molluscs characterized by a shell that is divided into two valves that are inter-connected to one another at a hinge. Bivalves are species that lack head and typical molluscan organs like radula and odontophore. Some of the primitive bivalves ingest sediments. The absence of the head and other molluscan organs of the bivalves can be explained by this largely sedentary and deposit-feeding or suspension-feeding lifestyle. Bivalves are also referred to as Lamellibranchiata and Pelecypoda in the scientific literature of the earlier centuries.

The majority of bivalves are marine and can be found in or on practically any substrate at any depth. Bivalves are common on rocky and sandy coastlines in shallow seas. Bivalves range in size from one millimeter (0.04 inch) to the enormous clam Tridacna gigas, which can grow to be more than 137 centimeters (54 inches) long. Bivalve species can be mainly categorized into clams, scallops, oysters, and mussels. Oysters are widely used for edible purposes by humans and other species. Also, bivalves are highly important in maintaining the marine food chain. Apart from marine habitats, bivalves are also seen in fresh water and brackish water.

Various species of Bivalvia are commonly seen on the Chennai coast. Some of them like Peacock mussel and White hammer oyster are used by the natives for edible purposes. Names and details of some of the bivalves common to the coromandel coast are listed below.

Ark Shell (Anadara Indica)

They are marine bivalvians belonging to the family, Arcidae. Arc shells are characterized by boat-shaped shells with long, straight hinge lines bearing many small, interlocking teeth. They are mainly found in tropical seas and hence are a common sight on the Chennai coast. They are harmless to human populations in any manner.

Two toned Cardita (Cardites bicolor)

Two-toned Cardita, known as “Vaṇṇa vari maṭṭi” in Tamil is another bivalve that is commonly seen in Chennai coast. As its name suggests, Shells of two-toned Cardita are in dual-tone. They are used for fisheries purposes and are harmless to human beings.

Cuneate Wedge Clam (Donax cuneatus)

This species is mainly seen in shallow water on beach sand. It travels between high and low tide marks with the tides, burying itself in the sand every time the waves expose it. it is usually about 2.5 cm long and is commonly found on the shores of Chennai.

Pen shell (Pinna bicolor)

Pinna bicolor is a species of bivalves belonging to the family Pinnidae. It is a tropical Bivalvia, majorly found in the Indian ocean. Henceforth it is a common sight on the coromandel coast.

Sunset Siliqua (Siliqua radiata)

Siliqua radiata is a Bivalvia belonging to the family Tellinidae) is commonly called a sunset shell. They inhabit the sandy bottom of beaches in small burrows.

Peacock Mussel (Perna viridis)

The Peacock mussel, is an economically important mussel, a bivalve belonging to the family Mytilidae. It is harvested for food but is also known to harbor toxins and cause damage to submerged structures such as drainage pipes. It is native in the Asia-Pacific region and is also common on the Chennai coast.

Dancette Clam (Sunetta scripta)

This species can be distinguished by its elongate anterior dorsal margin and slightly posterior umbo. The overall shape is elongate, ovate. The posterior margin is nearly straight and forms a distinct angle at its confluence with the ventral margin, and belongs to the family of Veneridae.

Windowpane Oyster (Placuna placenta)

The windowpane oyster (Placuna placenta) is a bivalve marine mollusk in the family of Placunidae. They are edible but valued more for their shells (and the rather small pearls). The shells have been used for thousands of years as a glass substitute because of their durability and translucence.

Trough Shell (Mactra sp)

Mactra is a large genus of medium-sized marine bivalve mollusks or clams, commonly known as trough shells or duck clams. The word “trough” in the common name refers to the fact that all Mactra shells have a large ligamental pit at the hinge line, which in life contains a large internal ligament. Most bivalves in other families have an external ligament instead.

 White Hammer Oyster (Malleus albus)

The White Hammer Oyster is one of the most unusual types of marine bivalve molluscs and is easily recognized by its greatly elongated hinge extensions and corrugated valves. Internally the shell valves exhibit a nacreous (pearly) appearance. The closely related species, the Black Hammer Oyster (Malleus malleus) has a much darker shell than the White Hammer Oyster, but sometimes occurs in the same localities

Tranquebar Scallop (Volachlamys tranquebaria)

A beautiful scallop is usually found in the Indian ocean at shallow depths. They come in an array of gorgeous colors and patterns. The first occurrence of the Tranquebar scallop Volachlamys tranquebaria in the Vellar estuary, southeast India is reported ith photographs.

Blue Button

by Goutham Krishna

Scientific name: Porpita porpita

Phylum: Cnidaria

Family: Porpitidae

Blue button, scientifically known as Porpita porpita is a marine organism found in the tropical and subtropical waters of the Pacific, Atlantic and Indian Oceans. These organisms are found on the western coast of India, which is bounded by the Arabian sea. They consist of colonies of hydroids found floating and propelling in the coastal sea waters. Their body is divided into two parts, which are the float and the hydroid colony. Float is the main body of the organism with a round / disc liked shape. The hydroid colony are elongated branches arising from the main body like tentacles. Hydroid colony is generally bright blue or yellow in color.  Carl Linnaeus was the first scientist to identify blue buttons in 1756.

Though they are commonly known as blue button Jellyfish due to their physical similarities with Jellyfishes, they are not genetically related to jellyfishes. Also, the blue buttons are organisms that cannot swim in ocean water. Instead of swimming, they are floated on the ocean surface with the assistance of winds and ocean currents. They are part of the neustonic food web, which includes all the organisms and species present on the surface of oceans. They hunt crabs and fish for feeding. Also, they are preyed on by various marine species like the sea slug, the blue dragon etc.

Blue button jellyfishes are hermaphrodites, i.e., with both male and female reproductive organs in the same species. Hence, they can produce sperms and eggs of their own. The mature polyps release eggs and sperm into the water, which fertilize on their own. After this, they turn into larvae which further develop into young polyps. These species communicate with each other with the help of pores present in its body.

These species are generally of zero economic and utilitarian importance to human beings. Though the stung of blue button jellyfishes are not seriously harmful to human beings, they can cause skin irritations. Due to global warming and the associated rise in oceanic temperature, a sudden rise in the population of Blue button Jellyfishes have been recorded in various parts of Earth. Overpopulation of these species is not good, considering their ability to create damage in the existing equilibrium of marine habitat.

The Ecological Engineers: The Lungs of the Sea

by Abdullah S

Seagrass are plants that grow in shallow waters of the ocean. They are similar to the flowering plants on the land. Monocotyledons are a group of plants like grasses, lilies, and palms. Seagrasses belong to Monocotyledons. It is often confused with seaweeds or algae but is different. They have a long oval or strap-like leaves with small flowers and roots. They are evolved from terrestrial plants. They need sunlight to prepare their food through photosynthesis. It is one of the reasons why they can mostly be found in ocean regions lagoons and bays where sunlight can directly pass through. Seagrasses are so-called for their long leaves identical to flowering grasses on land. They are 72 different species of seagrasses in four major classes. They can form dense underwater grasslands that can be seen from space. Seagrass beds provide food and shelter to a diverse range of marine creatures from small organisms to large fishes. Even though it lacks attention from people, it is one of the most effective and productive ecosystems in the world which provides numerous essential services to human beings. Due to the high rate of human interventions, the seagrass beds are tremendously decreasing. All around the globe efforts are going on to restore this highly important and amazing ecosystem.


Seagrass in India
Seagrasses can be found across the coastal regions of India. They are found densely in large areas of Palk Strait and the Gulf of Mannar in Tamil Nadu. Seagrasses can inhabit any type of surface from muddy to rocky. However, the lush green sea grasslands are found covering a dense area mostly in the muddy and sandy surfaces.

Seagrasses reproduce both sexually and asexually. The sexual method is called submarine pollination which is similar to the pollination that happens in terrestrial plants. The sexual method is done by branching off their rhizomes. This character helps them to recover after being eaten by natural grazers like dugongs, manatees, turtles and even destructed by storms.


Benefits of Seagrass
The seagrasses are known for many ecosystem services. Hence they are known as ‘Ecosystem Engineers’.

  • They have a great part in maintaining the water clarity. They trap the dissolved particles in the thick dense grass beds and increase the water clarity. They also filter the nutrients that are released from industries to the ocean.
  • They protect the sea bottom from intense wave actions from ocean currents and stabilize the sea bottom.
  • One square meter of seagrass can produce 10 liters of oxygen every day through photosynthesis. Hence seagrasses are known as ‘The Lungs of the Sea’.
  • Seagrasses act as a nutrient pump in the nutrient-poor region by absorbing nutrients from the soil and releasing it to the water through their leaves.
  • It is the foundation of the coastal food web. The large grazers like dugong, manatees, green turtles feed on the seagrass directly hence maintaining its crop short. Mesograzers like snails and crustaceans feed on the epiphytes and keep the seagrass clean. Dead seagrass feeds as food for decomposers who feed on decaying materials.
  • Air purification: the world seagrass cover absorbs up to 83 million metric tons of carbon every year.

A single acre of seagrass cover can support 40,000+ fish and 50 million small invertebrates. The green bed is home to small invertebrates, fishes, mammals, and endless marine animals. The list goes on…


• Industrial waste
• Propellers of vessels cutting seagrass to small sediments
• Chemical fertilizers and pesticides

Reynolds reviewed by Emmett Duffy and Nancy Knowlton, P. L. (2018, December 18). Seagrass and Seagrass Beds. Smithsonian Ocean. Retrieved November 16, 2021, from

Sundararaju , V. (2020, October 19). Why we must conserve the world’s seagrasses. Down To Earth. Retrieved November 16, 2021, from

Portuguese Man o’ War

by Goutham Krishna

Scientific name: Physalia physalis

Phylum: Cnidaria

Family: Physaliidae

The Portuguese man o’ war, commonly known as the “blue bottle jellyfish” is a marine predatory species, commonly found in the Atlantic and Indian ocean. It is an organism that usually lives in the ocean surface, with venomous microscopic nematocysts and feeding tentacles that are powerful enough to sting and paralyze mall fishes, pelagic crustaceans, and other invertebrates. These tentacles are normally 30 feet longer with the maximum length can extend up to 165 feet. Portuguese man o’ war is a species that is found mostly in tropical and subtropical ocean waters. They are reported to be seen in the coastlines of India and there were several incidents of visitors and natives in the shore being stung by this species.  Though the chances of a human getting killed by sting from these species are slim, there had been some incidents where unfortunate deaths have been reported due to the same.

Though these species are called blue bottle jellyfishes due to their similarity in appearance with jellyfishes, they are not genetically related to jellyfishes at all. They belong to the category of species known as siphonophores which are a colony of specialized species called zooids that work together as one. The man o war’s present in the Pacific Ocean (Pacific man o’ war) which are usually smaller than the common Portuguese man o’ wars in the Atlantic and Indian oceans are currently recognized as the same species though recent advancements in genetic studies are suggesting that they might be different species.

These species do not have the ability to swim in the water, instead of swimming, they use the winds and ocean currents to propel forward in the sea surface. Records suggest that the name “Portuguese man o’ war” is derived from a medieval naval reference. Since their species generally floats in the surface seawater and at that time has a reference to 18th-century Portuguese warships called man o’ wars.

Every colony of Portuguese man o’ wars have common and specific sex. Though marine biologists aren’t completely sure how the Man O’ War procreates, Mating generally occurs in the autumn season when the male and female colonies discharge sperms and eggs respectively in the water. The newly fertilized larvae of man o’ wars buds of new zooids of same-sex while growing and thereby forms a new colony.

The organism is translucent and appears in diverse colors including blue, pink, orange etc. where blue is most common. Man o’ wars has some predators of their own, including loggerhead turtle, The violet sea-snail etc. Portuguese man o’ war, due to its venomous nature are rarely used for any humane purposes at all. Hence, they are of very low economic and utilitarian values for humans.

Tides – Peculiarities & Significances

by Goutham Krishna

Tides are the long shallow-water waves generally found in the ocean and sea by the gravitational attraction of the moon, rotation of Earth and to a relatively lesser extent by the gravitational attraction of the sun. The imbalance between Earth’s centripetal force and the above-mentioned gravitational forces acting on Earth’s surface creates some residual forces in the Earth’s surface; the horizontal component of these residual forces pushes ocean water into two equal tidal bulges in the opposite sides of Earth. These bulges are accountable for the formation of tides.

The regular rise and fall of the ocean’s water are referred to as high and low tides. High tides happen when water covers most of the shore after rising to its highest level whereas the low tides are characterized by the retreat of water to its lowest level, moving away from the shore. The rotation of tidal bulges according to the change in the moon’s position is responsible for the phenomena of high and low tides. According to the occurrence of high and low tides on a lunar day, the tidal cycle can be divided into diurnal, semi-diurnal and mixed. A tidal cycle with two nearly equal high tides and low tides per lunar day is called a semi-diurnal tidal cycle, whereas a tidal cycle, one each high and low tides per day is called diurnal. A mixed tidal cycle is when two unequal high tides and low tides occur per lunar day.

India has a total coastline of 7516.6 km in total, with the mainland having 5422.6 km coastline. The Indian mainland can be divided into the east coast and west coast according to its geographical location, where the east coast is bounded on the east by the Bay of Bengal and the west coast is bounded on the west by the Arabian sea. Both east and west coasts of India experience two high tides and low tides per day, but the tidal cycle of the east coast is semi-diurnal whereas that of the west coast is mixed.

The forecasted schedule of high tides and low tides of Chennai coast, which belongs to the southeast coastal line of India is given below,

The role of tides in balancing and maintaining marine life and the ecosystem is pivotal. We can find numerous marine flora and fauna that are highly dependent on tides and tidal patterns for their survival. There are many fishes, which depend on the tides for their food. These fishes wait for the tides to wash smaller fishes into the sea or to pull them to the areas where food is abundant. The migratory and feeding patterns of many fishes are directly linked with the tides. Also, there are various seabirds that catch fish depending on the tides. Moreover, the phenomena of tidal pools; which are the isolated pockets of rocks and seawater found in the intertidal zones, can host diverse marine species and vegetation. But at low tide zones, these species are exposed to sunlight and predators at varying degrees.

Apart from these, tides are also important as they have the potential to become a regular energy generator in the near future. Tidal energy is naturally abundant and renewable and more importantly, is an emission-free energy source. Presently there are 8 operational tidal energy power stations in the world and many are under construction and planning. India is planning to build a tidal power station in the Gulf of Kutch and the project is now in its R&D (research and development) stage. Hence tides will be a trump card in the future, for building resilience against climate change and its after-effects.

Coral Reefs of India

by Goutham Krishna

Coral reefs are a unique underwater ecosystem composed of reef-building coral species. Coral reefs are considered the most diverse and rich marine ecosystem on the planet, hosting about 25% of all marine species within an area less than 0.1% of the world oceans. Due to this peculiarity of the coral reef ecosystem, they are often called the rainforests of the sea. Reef-building corals are mainly found in shallow tropical and subtropical waters due to their biochemical requirements.

India, being centrally placed within the warm and tropical Indian ocean, therefore, exhibits the presence of Coral reef colonies in its marine territories. The main coral colonies in India are the Gulf of Kachchh, Lakshadweep, Palk Bay & Gulf of Mannar and Andaman and the Nicobar Islands. According to a study, the total area of coral reefs in India is estimated to be 2375 square kilometres. The three different types of reefs present in India include,

-> Fringing reefs: Reefs that are directly attached to the shore and spread towards the sea.

-> Barrier reefs: Separated from the landmass by a lagoon

-> Atolls: Continuous barrier reefs that extend all the way along a lagoon without any central islands

Coral reef colonies in India – Source: Research gate

As mentioned in the introductory part, coral reefs are rich in species diversity. The exact number of reef species present in the world is still unknown. The coral reefs of India are also hotspots of extraordinary biodiversity. According to a study done by Venkataraman, Indian reefs have a total of 199 species, recorded from 37 genera. Reefs in Andaman & Nicobar area are the most diverse coral reef ecosystem present in India, whereas the species diversity is relatively lower in the Gulf of Kachchh.

Coral reefs in Andaman – source:

Apart from the biocentric significances, coral reefs are important for human beings as they provide various value additions and services to humankind. The reefs have an undeniable role in industries like fisheries, pharmaceutical and minerals, tourism and allied sectors etc. Also, they provide various ecosystem services such as protection of the coastline, maintenance of air quality and Filtration of nearshore waters.  Hence coral reefs have direct and indirect impacts on the economy and livelihoods at an individual and societal level. In this context, the need to sustainably conserve coral reefs from degradation becomes of prime relevance.

Presently, coral reefs in the world are facing different types of threats which are either natural or anthropogenic. Climate change and its impact on the natural equilibrium is hampering the status of coral reefs also. Variation in content of salinity and pH in ocean water, increased sediment deposition, change in temperature pattern etc. are some of the natural threats faced by coral reefs whereas anthropogenic activities like Mining, bottom fishing, Ocean pollution, unsustainable tourism etc. intensifies their extent.

The situation of Coral reefs in India is no different. Experts estimate that three fourth of the coral reefs in India will be endangered by 2030 if no progressive measures are taken to conserve them. A multi-stakeholder approach to managing and conserving the coral reef system of India is immensely important. Scientific and sustainable approaches to protect the rainforests of oceans must hence be an urgent priority for us.