Category Sea/Ocean

As fish populations decrease globally, researchers assert that the focus should be on working with other countries rather than on just local numbers. Why is that? Come, let’s find out.

Political boundaries are the work of humans. Wildlife do not recognise them. And, fish are no different. Dwelling in water bodies, they freely cross countries. Studies have indicated that there a few fish species that “migrate over long distances”. As it happens, fish egg and/or larvae may originate in one place and be carried to faraway places (this could be to even other countries), thanks to ocean currents. “Often one nation’s fish stocks depend on the spawning grounds of a neighboring country, where fish release eggs and sperm into the water and Larvae hatch from fertilized eggs.”

A recent study has discovered that “global fisheries are even more tightly connected than previously understood”. With fish and spawn connected to several regions, the world’s coastal marine fisheries are essentially “a single network”, aided by ocean currents. Ocean current patterns vary with seasons. But, mostly these currents are sluggish (though there are a few regions where the currents are faster). Despite this, spawn can travel far. Here’s an example. “Even a gentle current of 0.1 miles per hour can carry spawn 40 miles over a month, and some species can float for several months.” Add to this the fact that different “fish species spawn in different seasons, and a single species may spawn in several months at different locations”, and what we get is fish species in one country steadily arriving from or drifting to other countries over different periods of time.

So what happens is that if fish populations in one region dwindle. “the amount of fish spawn, or eggs and larvae, riding the ocean currents from there to other countries would also decline dramatically, resulting in further loss of fish elsewhere”. To ensure food security and employment to those dependent on fishing, it is important for countries to understand this deep interconnectedness of global waters and chalk out ways to guard them.

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Imagine a forest underwater or a tapestry of green inside the ocean. That’s just what a kelp forest is. Though kelps are considered the forests of the sea and look like plants, they are not plants. Kelps are large brown algae, and together, the different species of kelps form kelp forests.

The kelp forests figure among one of the most dynamic and diverse ecosystems on earth and offer a habitat for marine organisms such as invertebrates, fishes, and other algae and play many key ecological roles.

Kelps cover 25% of the world’s coastlines. They provide food and shelter to marine animals. These can be seen around the world, across polar as well as temperate coastal oceans. They live in cold waters that are rich in nutrients.

While they remain attached to the seafloor, they grow towards the surface of the water and depend on sunlight to generate food. If the ideal physical conditions are satisfied, then kelps can grow 45 cm a day. Some of these species are seen to measure up to even 45 m long.

Kelps and climate change

Kelp forests play a highly crucial role in battling climate change as they are good at sequestering carbon, thereby ensuring the health of the coastal environment. They are also capable of absorbing excess nitrogen and phosphorus that run into the oceans from the land.

Studies have shown that a third of the globe’s coastal environments depend on kelp to combat local pollution and sustain fisheries. Apart from helping maintain the health of the marine ecosystem, kelps are also commercially harvested as they find applications in food production, textiles, pharmaceuticals, and so on.

The health of the kelps is dependent largely on oceanographic conditions and as such they can disappear and reappear based on this. For instance, sea urchins can destroy the kelp forests. Moreover, strong individual storms can affect the kelp forests by tearing out the kelps from the floor of the sea.

These dense canopies of algae are also facing many threats. Water pollution, rising sea temperatures, overgrazing, overfishing, and water pollution are some of the reasons for the depletion of kelp forests.

Studies prove that Southern Australia and Northern California have lost 95% of their kelp forests.

Their depletion is seen along the coastlines of every continent and this affects the fish, livelihoods and economy that are supported by the kelp forests.

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The longest species of seaweed is the giant kelp Macrocystis pyrifera. It is found near the Californian shore and in different parts of the world near the Pacific Ocean. The longest specimen that has been verified is 60 metres long but unofficial reports say that even longer specimens have been found.

They form large and dense kelp forests, which become habitats for a number of different marine species. They are often located in cold and clear waters, where they resemble tall grass although they are not part of the grass family. It is a type of brown alga and belongs to the large kingdom of Protista. Since kelp is not a plant, it does not have roots and obtains its nutrients from a structure called a holdfast by which it attaches itself to the rocky bottom of the ocean. But kelp are similar to plants by the fact that they use photosynthesis to harvest the Sun’s energy and do not feed on other organisms to keep themselves alive. They are also one of the fastest growing species and are known to grow up to 60 centimetres in a single day when given perfect conditions. Strikingly, when the kelp reaches the sea surface, it grows horizontally and floats as large mats that shade the water column and the sea floor below it.

The kelps also become a source of nutrition once they decompose in the sea bed. Sea otters even use these giant kelps to avoid being floated away while they sleep.

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The Great Barrier Reef covers an area of 348,000 square kilometres, and is the longest and largest reef complex of the planet. In fact, this remarkable site is one of the seven wonders of the natural world. Located on the north-east coast of Australia, the Great Barrier Reef is home to a huge diversity of species and habitats. This ecosystem is intricately interconnected, making it one of the richest and most complex natural ecosystems on earth.

It is home to over 1,500 species of fish, 400 species of corals, and 4,000 species of molluscs. It also hosts 240 species of birds along with a number of sponges, anemones, marine worms, crustaceans, and other species. This giant marvel is also home to many endemic and threatened species listed by the International Union for Conservation of Nature (IUCN). These features make it a very popular tourist destination and thus contribute to the economic development of the country.

In order to safeguard and preserve the reef, it was declared as the Great Barrier Reef Marine Park in 1975, and the supervision of the park was handed over to the authorities of the Marine Park.

Owing to its significance in the ocean ecosystem, the Great Barrier Reef was added to UNESCO’s World Heritage List.

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Occupying about one-third of the surface of the planet, the Pacific Ocean is the largest ocean on earth. It lies between the continents of Asia and Australia on the west and is bordered by North America and South America on the east. It covers an area of 161.76 million square kilometres without counting in the South China Sea. It has double the area and more than double the water volume of the next largest water-body, the Atlantic Ocean. It covers more area than the total land surface of the globe.

The Pacific Ocean meets the Arctic Ocean in the Bering Sea in the Northern Hemisphere and in the Southern Hemisphere, it mixes with the Atlantic Ocean in the Drake Passage between Tierra del Fuego in South America and Graham Land in Antarctica.

One cannot clearly say where the Pacific and Indian oceans become separate, but a line of islands extending eastward from Sumatra, through Java to Timor, extending across the Timor Sea to Cape Londonderry in Australia is usually considered as the points of separation of the two. The deepest point in the Pacific Ocean is in the Mariana Trench. It is located in the western Pacific located around 200 kilometres east of the Mariana Islands to the east of the Philippines.

The Pacific Ocean Basin also contains 75 per cent of the world’s volcanoes and forms the Ring of Fire, which is a ring of Pacific Ocean volcanoes around the ocean basin. There is also an interesting story behind the name of this ocean.

It was Ferdinand Magellan, who gave the name Pacific inspired from the Latin word ‘pacificus’ meaning ‘tranquil.’ It is said that he felt the ocean to be unusually calm as he entered its waters and this led to the name.

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A 400-million Euro, 500-MW project to generate heat for the Finnish capital will use seawater from the Baltic even when the sea surface is frozen.

Seawater will be carried to the heat exchangers via a 17-km tunnel being bored from the Baltic seabed – where the temperature is a constant 2 degree C year round. Heat exchangers will transfer and concentrate the heat from the seawater-which is returned to the sea through a nine-km tunnel-to the district heating system where it will reach around 88 degree C.

Already home to the world’s largest heat pump, Helsinki is aiming to become carbon neutral by 2050, and the new pump alone is expected to provide up to 40% of the city’s heating requirements when it goes online in around 2029. A utility company currently provides around 8% of Helsinki’s heating through recovering heat from waste water and the excess from data centres and other buildings.

Frequency converter technology plays an essential role in heat pump product development. ABB’s frequency converters increase the efficiency of Oilon’s heat pumps in almost all of its sites in Helsinki. Frequency converter control can be used for the variable rotational speed control of a heat pump compressor.

“A heat pump must be able to handle different load and temperature conditions. Frequency converter control enables precise control and a large partial capacity range,” Martti Kukkola explains.

Frequency converter technology has Finnish roots – the first frequency converter developed by the engineers of Strömberg controlled the speed of metro trains in Helsinki. In ABB’s hands, the technology has evolved into an extensive frequency converter range, and ABB Finland is responsible for the technology’s global product development.

“Our reasons for choosing ABB are reliability, an extensive range, and equipment that is functional from a techno-economic perspective,” Kukkola says.

Using Oilon’s and ABB’s technologies, Helen has been able to provide its customers with more energy-efficient solutions to cover heating and cooling needs. Valuable heat is produced in a climate-friendly way as a by-product of cooling.

“As a technology leader, we want to be the trailblazer for energy efficiency, and by cooperating with partners, we can do more and have a greater influence in this area. It is valuable to be able to build a more sustainable future with Oilon and Helen by combining Finnish innovation expertise,” says Mika Männistö, Sales Director, ABB Motion Finland.

Energy-efficient frequency converters and motors offer substantial potential for cutting greenhouse gas emissions. ABB encourages all stakeholders to cooperate within the framework of the Energy Efficiency Movement to bring about a comprehensive reduction in energy consumption.

Credit : Energyefficiencymovement.com

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So much of our oceans is still unexplored and remains a mystery. In fact, it is safe to presume we know more about the surface of Mars than about Earth’s seafloors! But whatever  we little know of life in ocean depths is intriguing, fascinating, and incredible. The deep oceans are low on sunlight and plants but high on pressure, and yet, several creatures call this space home. Here’s a glimpse of how they have adapted to life in unforgiving conditions.

Colours that help

Since they dwell in open waters without plants or rocks to hide under to safeguard themselves from predators, many creatures benefit from disguise. Some of them are red. rendering them difficult to spot since red light does not penetrate those depths. Some others are transparent, again tough to spot. Many others are bioluminescent, a good tool to confuse predators.

Heard of sea snow?

Since ocean depths hardly have any plant, finding “live meal” is a tough task. Apparently, the duration between two live meals can be even up to three weeks for a marine creature! That’s where marine snow or sea snow comes into play. When no live meal is available, the next best thing to turn to is the dead. Organic particles from the surface waters – disintegrated bodies of animals and plants, mingling with fecal matter-drift down in what is known as “marine snow”.

What is chemosynthesis?

At the cracks between oceanic plates are hydrothermal vents – these are the hot springs on the ocean floor. These vents send out chemical compounds such as hydrogen sulphide. These chemical compounds are used for preparing food – much like sunlight is used in photosynthesis. This process used by microorganisms such as bacteria to create food (such as glucose), is called chemosynthesis.

Though humans still don’t have a complete understanding of ocean depths, we’re definitely leaving our mark there- and, sadly, not in a good way. With global warming, over-fishing, and pollution, we’re changing the composition of the oceans they are acidifying, and hosting crustaceans with microplastics, as far deep as the Mariana Trench, the deepest location on Earth.

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A dip in the waters in the Hirsholm islets off the northern shores of Denmark is like diving into a giant aquarium. Amidst the dazzling colours of its vibrant marine life, tiny bubbles from the seabed soar to the surface like clear blobs. The unique phenomenon is caused by the presence of methane gas. The gas was probably formed due to the microbial decomposition of plants deposited thousands of years ago under the sea. As the gas seeped up through funnels in the floor, chemical reaction with underwater microbes hardened the sand particles into sandstone structures. Water currents washed away the surrounding loose sand, leaving behind solid stone columns, arches and slabs, which became thriving hubs of plant and animal life. The methane constantly bubbles out through vents in these columns, resembling air bubbles in a fish tank. The site is an important centre of marine biology.

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Important ocean habitats that offer us compelling evidence about the risks posed by climate change, coral reefs are large underwater structures made up of the skeletons of colonial marine invertebrates called coral. Also referred to as “the rain forests of the seas”, scientists believe that one out of every four marine species live in and around coral reefs. This makes them one of the most diverse habitats of the planet, providing for a huge portion of Earth’s biodiversity.

Each individual coral is referred to as a polyp. Coral polyps live on the calcium carbonate exoskeletons of their ancestors, adding their own exoskeleton to the existing coral structure. As the centuries pass, the coral reef gradually grows, one tiny exoskeleton at a time, until they become massive features of the marine environment.

Corals are found all over the world’s oceans, from the Aleutian Islands off the coast of Alaska to the warm tropical waters of the Caribbean Sea. The biggest coral reefs are found in the clear, shallow waters of the tropics and subtropics. The largest of these coral reef systems, the Great Barrier Reef in Australia, is more than 1,500 miles long (2,400 kilometers).

Scientists have explored only about 20 percent of the ocean’s floor, according to the National Oceanic and Atmospheric Administration (NOAA). As such, ocean explorers continue to discover previously unknown coral reefs that have likely existed for hundreds of years.

Most of the substantial coral reefs found today are between 5,000 and 10,000 years old, according to CORAL. They are most often found in warm, clear, shallow water where there’s plenty of sunlight to nurture the algae that the coral rely on for food.

Coral reefs cover less than 1 percent of the ocean floor — all the reefs combined would equal an area of about 110,000 square miles (285,000 square km), only about the size of the state of Nevada. Nonetheless, they are among the most productive and diverse ecosystems on Earth.

About 25 percent of all known marine species rely on coral reefs for food, shelter and breeding. Sometimes referred to as “the rainforests of the sea” for their biodiversity, coral reefs are the primary habitat for more than 4,000 species of fish, 700 species of coral and thousands of other plants and animals, according to CORAL.

Coral reefs are typically divided into four categories, according to CORAL: fringing reefs, barrier reefs, patch reefs and atolls. Fringing reefs are the most commonly seen reef and grow near coastlines. Barrier reefs differ from fringing reefs in that they are separated from the coastlines by deeper, wider lagoons. Patch reefs typically grow between fringing and barrier reefs on the island platform or continental shelf. The rings of coral that make up atolls create protected lagoons in the middle of the oceans, typically around islands that have sunk back down into the ocean.

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Scientists have discovered the world’s largest plant off the Australia coast- a seagrass meadow that has grown by repeatedly cloning itself. Genetic analysis has revealed that the underwater fields of waving green seagrass are a single organism covering 180 sq.km. through making copies of itself over 4,500 years.

Scientists confirmed that the underwater meadow was a single organism by sampling and comparing the DNA of seagrass shoots across the bed, wrote Jane Edgeloe, a study co-author and marine biologist at the University of Western Australia.

A variety of plants and some animals can reproduce asexually. There are disadvantages to being clones of a single organism. such as increased susceptibility to diseases- but “the process can create hopeful monsters” by enabling rapid growth, the researchers wrote.

The scientists call the meadow of Poseidon’s ribbon weed “the most widespread known clone on Earth”, covering an area larger than Washington, the US.

Though the seagrass meadow is immense, it’s vulnerable. A decade ago, the seagrass covered an additional seven square miles, but cyclones and rising ocean temperatures linked to climate change have recently killed almost a 10th of the ancient seagrass bed.

Did you know?

• The species is commonly found along parts of Australia’s coast, and grows “like a lawn” up to 35 cm a year, Which is how they arrived at this plant’s age.
• This specific plant is believed to have spread from a single seed.
• The plant is hardy, growing in different types of conditions within its present location – from a variety of temperatures and salinities to extreme high light conditions, all of which would have been very stressful to most other plants.
• A place in the Guinness World Records

The Poseidon’s ribbon weed has entered the Guinness World Records as the “largest single living organism based on area”. The weed has claimed its title from a honey mushroom, which is spread over 2,385 acres in the U.S. The mushroom is still “the world’s largest fungus”.

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The octopus is a surprisingly complex creature and, quite possibly, the world’s original “blue blood.” Its 500 million neurons are distributed throughout its head and body, compared to the 100 billion neurons in our brains. The octopus’s brain power isn’t easily apparent at first glance, but it’s proven itself capable of planning, reasoning and — predicting sporting matchups. On the planning front, researchers have discovered that octopuses in Indonesia will gather coconut shell halves in preparation for stormy weather, then take shelter by going inside the two pieces of shell and holding it shut.

So what makes these smart sea creatures so adaptable? The ability is literally in their blood. The same pigment that gives the octopus blood its blue color, hemocyanin, is responsible for keeping the species alive at extreme temperatures. Hemocyanin is a blood-borne protein containing copper atoms that bind to an equal number of oxygen atoms. It’s part of the blood plasma in invertebrates.

Blue-hued hemocyanin binds to oxygen in the blood and transports it throughout the octopus’s body to supply tissues, a critical factor in its survival. Octopuses have three hearts and need more oxygen than most other invertebrates, so the hemocyanin allows octopuses to get a steady oxygen supply, even when it isn’t readily available in their environment. It also ensures that they survive in temperatures that would be deadly for many creatures, ranging from temperatures as low as 28 degrees Fahrenheit (negative 1.8 degrees Celsius) to superheated temperatures near the ocean’s thermal vents.

Researchers suspect the “blue blood” adaptation is the result of the octopus’s inability to migrate away from challenging environmental conditions.

Credit : How stuff works

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The blue-ringed octopus may look cute and harmless at the first glance. But take care; it is an extremely poisonous animal!

These small octopuses are common in coral reefs and tide pools of the Pacific and Indian Oceans. They usually stay hidden in crevices, shells or marine debris, their tan-coloured body blending in with the surroundings. But the ‘true colour’ of this shy little thing comes out when threatened by somebody. Bright blue rings appear all over its body as a warning signal, which have given it the name.

If a human is bitten by the blue-ringed octopus it can cause respiratory distress and paralysis and other symptoms too, like nausea, blindness and heart failure.

The venom is not just to fight the enemies, it helps in feeding too. These octopuses usually hunt small crabs and shrimp, but will also eat molluscs and small fish. The octopus delivers the paralyzing venom into the prey. The venom is produced by its saliva, which also contains digestive enzymes. So the flesh of the prey is partially digested before the octopus sucks it out. The blue-ringed octopus is not hurt by its own venom.

The box jellyfish feeds on prey like fish and shrimp, but it does not want their escape struggles to damage its delicate tentacles. So the jellyfish uses its powerful venom to stun or kill the prey instantly. The venom of the box jellyfish is among the most deadly in the world, attacking the heart, nervous system and skin cells. Humans struck with this venom sometimes go into shock and drown before reaching shore. The survivors have to endure intense pain for weeks, and carry scars where the tentacles touched. These jellyfish do not fire venom at anything that the tentacles touch. The stinging cells only react to some chemicals on the skin, so there’s no wastage of their weapon!

Also known as sea wasps and marine stingers, these deadly jelly-fish mostly live in the coastal waters near Northern Australia and in the Indo-Pacific. The box jellyfish are so named because of their cube-like shape. This group include various species of various sizes; the largest measuring about a foot across, and with tentacles about ten feet long. Some divers use tight-fitting clothes that cover the whole body to escape their venom.

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The Mediterranean Sea holds a wonder that beats all – something that never dies! It is a jellyfish whose scientific name is Turritopsis dohrnii.

Jellyfish start their lives as larvae, which attach themselves to a suitable place like a rock. Then they are transformed into polyps that have a small body with tentacles. These polyps then clone themselves to form others and create a colony, or a medusa, which is the jellyfish.

When this jellyfish dies, or is physically damaged, the decaying cells form new polyps, and later return to their jellyfish state. This way they could live forever under the right conditions! However, they don’t actually achieve immortality because these tiny wonders are eaten by fish or other animals, or die by other means.

Although the jellyfish has ‘fish’ in its name, it is not fish. It is not made of jelly either. Unlike a fish, it is an animal without a backbone found in oceans and seas around the world. The name jellyfish derives from the jelly-like bodies of these animals. Jellyfish are found in oceans and seas all over the world, in the deepest as well as in shallow water.

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Meet someone whose body tells his own life’s story that runs into centuries! The ocean quahog, a bivalve mollusc that can live more than 500 years, is the longest-lived solitary animal.

The shell of an ocean quahog is a treasure-house of information for scientists. Its shell grows periodically throughout life and the growth patterns visible on the shell function as a calendar. They help not only to tell the age of the animal, but also to know more about the marine environment in the past. For example, scientists would be able to tell from the shell of a quahog, how warm the seas were two centuries ago! The quahogs are the only surviving species of a family of similar claims that had lived during the Dinosaur era!

The ocean quahog (Arctica is landica) lives in the North Atlantic Ocean, buried in sandy sea beds. It feeds on the organic matter it gets by filtering water using its siphon. Interestingly, their feeding activity seems to depend on how much light is available! Thus, in the northern-most regions where they are found, they mostly feed during eight months of the year. During the remaining months, they feed for only a few days.

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Urchin usually means a young child who is raggedly dressed and behaves badly. But sea urchins get their name from an old meaning of this word – the hedgehog. Sea urchins have a globular body that is full of spines, like a hedgehog.

The sea urchins belong to a group called echinoderms, or spiny-skinned marine invertebrates. The largest of this species are the red sea urchins, whose outer skeleton can have a diameter of more than 18 cm and spines, a length of up to 8 cm. They are a colourful sight under the sea, varying between a uniform red and dark burgundy, crawling slowly over the sea bottom using their spines as stilts.

The sea urchins are among the longest-living animals, with a life span of over 100 years. But that does not mean that they don’t face any danger in the sea. They are eaten by some fish like the wolf eels, sea stars, crabs etc. Large adults, of course, are often left alone by these predators. But sea otters eat even the largest sea urchins, cracking them on rocks. Young sea urchins usually seek shelter under the spines of the adults, and emerge only when they reach approximately 5 cm in diameter.

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Everybody loves a good pearl. Did you know that the mussel it comes from is admirable, too?

The freshwater pearl mussels are one of the longest-lived invertebrates. Scientists have determined that they can live for up to 210-250 years. Scientifically known as Margaritifera margaritifera, these are bivalve molluscs, meaning they have a compressed body enclosed within a hinged shell. Inside the shell is a thick, iridescent layer called the mother-of-pearl. The freshwater pearl mussels live on the beds of fast-flowing rivers, feeding by taking in water and ingesting any fine organic matter that comes with it.  Just imagine, an adult mussel can filter more water in a day, than what you use for a shower! They live seemingly safe, partly buried in sand or gravel. Yet, they are never safe because of the fine-quality pearls they can produce. Humans have always exploited them in the search for pearls, and these mussels have now become an endangered species.

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Yes, they do! In fact the rougheye rockfish are among the longest-lived marine fish species, some of them recorded as old as 205 years. They grow very slowly, and mature late in life.

Does the name of this fish strike you as strange? They really have ‘rough eyes’, because of spines along the lower rim of the eyes. They are also nicknamed ‘blacktip’ rockfish because their pectoral fins have black ends.

The rougheye rockfish live in the Pacific Ocean, from northern Japan and the Bering Sea to southern California. They usually live at depths between 170 to 660 metres, near the seafloor around caves, crevices and boulder fields. They feed mostly on shrimp, but also go for crabs, tiny crustaceans and other fish. The females usually spawn between February and June, releasing larvae from their ovaries. These fish grow to a maximum length of about 97 cm, and their record weight is 6.7 kg.

For most part of the year, the larger fish remain solitary or roam in small groups, but during some periods, the rougheye rockfish form schools.

For most part of the year, these fish remain solitary, but during some periods, the rougheye rockfish roam around in schools (group).

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The newly hatched, or neonate, ghost shark was found at a depth of 1200m off the east coast of New Zealand’s South Island. The rare discovery of a juvenile ghost shark off New Zealand’s South Island coast will help researchers better understand the biology and ecology of this mysterious deep water fish.

Ghost sharks or chimaeras are one of the most elusive fish species in the world. They have existed for hundreds of millions of years, but not much is known about them because they usually reside at depths of up to 2,000 metres. The neonate or hatchling was found at a depth of 1,200 metres.

Ghost sharks, also known as ratfish, spook fish or rabbitfish, are not actual sharks but are closely related to sharks and rays. They are cartilaginous, meaning their bodies have stiff armour-like plates and bone-like cartilage. Adult ghost sharks have venomous spines in front of their dorsal fins. Embryos grow inside their egg capsules on the sea floor and feed off the capsules until ready to hatch (between 6 to 12 months).

Critical missing details about the species’ life cycle makes monitoring chimaera populations difficult. Sixteen per cent of all ghost shark species are threatened or near threatened.

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If an award was given for the most easy-going and placid animal in the water, it would definitely go to the manatee. Manatees look like giant, elongated lumps of dough with large paddle-shaped tails and wrinkled heads.

They have whiskers growing from their chins and rectangular, nail-tipped flippers. Usually grey or brown in colour, the manatee is one of the most friendly and curious creatures you can encounter underwater.

These plant-eating herbivores graze on sea grasses and other aquatic plants. These gentle giants are also called ‘sea cows’ because of their docile dispositions. They can grow to a length of up to 13 feet and weigh about 590 kg.

They can hold their breath for up to 20 minutes underwater, but usually come up every 2 to 3 minutes to breathe. They spend their time resting for up to 12 hours suspended near the surface of the water or lying on the bottom of shallow, slow-moving rivers, saltwater bays and canals. However, they are capable of reaching speeds of up to 25 km/h, in short bursts, when required.

These marine mammals look like oversized otters or seals but are actually more related to elephants! They are so friendly that it sometimes gets them into trouble! Manatees will swim over to any curious looking object (like a passing boat) and try to examine it. Consequently, many of them get cut by propeller blades and bear the scars on their backs.

They are found in the shallow, marshy coastal areas and rivers of the Caribbean Sea, the Gulf of Mexico, the Amazon basin and West Africa. They cannot survive in temperatures below 60 degrees, which is why they migrate from the open waters of the Gulf of Mexico to natural springs in Florida during the winter months.

The main challenges for manatees are human-related issues, such as habitat destruction and manmade objects such as boats and ships. Other threats include adverse temperatures, predation by crocodiles on their young and diseases. Their numbers are declining and they are listed as ‘Threatened’ in the IUCN List.

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The Shortfin Mako Shark is found in tropical and temperate seas all over the world. It has a streamlined bullet-like shape and small dorsal fins (as its name ‘shortfin’ suggests) that minimize drag, making it an extremely fast swimmer.

It can grow to a length of 3 metres and weigh around 135 kg.

At speeds of 50 km/h, it is one of the fastest sharks in the ocean. It is metallic blue on top and white below. It has large, well developed eyes and a mouthful of teeth. In fact its name ‘Mako’ comes from the Maori language and means tooth or shark tooth. The Maori tribes of New Zealand prize Mako teeth and use them to make necklaces and traditional jewellery.

The Mako is an extremely aggressive and energetic fish. Anglers, who have experienced a Mako Shark at the end of their line, liken the experience to wrestling with an angry crocodile! A hooked Mako will not give up easily and takes a series of flying leaps into the air struggling with the line. Sometimes it will even land on top of the angler and the boat!

This shark also leads an eventful life in the ocean. It preys on and attacks swordfish and will often enter into a battle with these dangerous adversaries. Mako sharks are often seen with swordfish stabs and puncture wounds in their body and some even have broken pieces of the swordfish bill lodged in their heads!

This deadly and beautiful predator was once abundantly found in the world’s oceans. Overhunting by recreational anglers as well as for commercial consumption has brought its population down drastically. It is currently listed as ‘Endangered’ on the IUCN List.

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A swordfish is a long, scaleless fish with a sword-shaped bill and a large dorsal fin. Its bill is flatter as compared to the marlin and the sailfish and is thus also called ‘broadbill’. It can grow up to 10 feet long and weigh as much as 650 kg! It is a highly elusive, migratory and solitary fish.

It reaches a top speed of about 120 km/h and preys on other fish such as lantern fish, cuttlefish, squid and herring. It has special organs near its eyes that heat up its eyes and brain in the cold water. This helps it to see better and hunt more effectively.

The swordfish prefers to hunt alone at night and likes to swim around in deep waters. It is an apex predator with very few threats except sharks and humans. The swordfish, like all billfish, can have high levels of mercury in their bodies as they hunt on smaller fish. The mercury from these small fish gets deposited over the years in the swordfish.

Although swordfish is considered a delicacy and many restaurants serve it on their menu as a special dish, eating it should be avoided by children, pregnant women and sick people.

Swordfish populations were declining at one point due to overfishing but since then have recovered. They are now listed under ‘Least Concern’ in the IUCN List.

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Sailfish, marlins and swordfish are part of the billfish family – all apex saltwater predators. Like marlins, the sailfish is one of the fastest fish in the ocean, reaching speeds of about 112 km/h!

It gets its name from its huge sail-like dorsal fin that allows it great manoeuvrability and speed in the water. It is able to retract this sail when required (much like the sail on a real ship!) and uses this fin as a shield to trap small prey and prevent them from escaping. Additionally, like the marlin, it uses its elongated bill to pierce and slash its prey! Its bill also allows it to cleave through the water and contributes to its streamlined shape.

It feeds on sardines, anchovies, squid and octopus. Females are much larger than the males. They can reach a length of about 3 metres and weigh up to 100 kg. They breed in large numbers and are not under much threat in the ocean from predators or humans. They are listed under ‘Least Concern’ in the IUCN List.

Sailfish are capable of changing their colour in order to communicate or while hunting prey. Often they will sneak up on unsuspecting fish before the prey sees it.

They are valued as game fish and are often caught for sport, not meat. They are often very difficult to reel in as they put up a fierce fight that may last for hours! One could say that these are one of the most redoubtable opponents that humans face in the ocean.

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THE COELACANTH (PRONOUNCED SEEL-uh-kanth) is an enormous, bottom-dwelling fish that is unlike other living fishes in a number of ways. They belong to an ancient lineage that has been around for more than 360 million years. Coelacanths can reach more than six feet long and weigh about 200 pounds, and they’re covered in thick, scaly armor. It’s estimated they can live up to 60 years or more.

There are two living species of coelacanth, and both are rare. The West Indian Ocean coelacanth (Latimeria chalumnae) lives off the east coast of Africa, while the Indonesian coelacanth (Latimeria menadoensis) is found in the waters off Sulawesi, Indonesia. They are the sole remaining representatives of a once widespread family of lobe-finned fishes; more than 120 species are known from the fossil record.

Their jaws are hinged to open wide. Unique to any other living animal, the coelacanth has an intracranial joint, a hinge in its skull that allows it to open its mouth extremely wide to consume large prey.

They have tiny brains. A coelacanth’s brain occupies only 1.5 percent of its cranial cavity. The rest of the braincase is filled with fat.

Credit: wired.com

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The leatherback sea turtle is the largest turtle species on Earth. Found in almost all the oceans, it can grow up to 2 metre long and weigh up to 1.000 kg! It is also the only turtle species to not have a hard shell; its shell is leathery.

Unlike other sea turtles, the bony shell of the leatherback is not visible. Instead it’s covered by a leathery layer of black or brown skin, hence the turtle’s name. The shell has seven ridges running from front to back. Leatherbacks are the largest of the seven living sea turtle species, growing to more than 6.5 feet (two meters) in length and weighing up to 2,000 pounds (900 kilograms). Leatherbacks are found in tropical and temperate marine waters all over the world. They live off both the east and west coasts of the United States, and also in Puerto Rico, the Virgin Islands, and Hawaii. Leatherbacks spend most of their lives at sea and sometimes look for prey in coastal waters. Leatherbacks have been documented diving deeper than 4,000 feet (1,200 meters). By contrast, scuba divers typically descend to only about 100 feet (30 meters). Additionally, the Pacific leatherback is the fastest aquatic reptile and can reach speeds of 22 miles an hour (35 kilometers an hour).

Jellyfish make up the biggest portion of their diet, but they also eat seaweed, fish, crustaceans, and other marine invertebrates. Leatherbacks have downward-pointing spines in their throat, which allows jellyfish to be swallowed, but prevents them from coming back up. The migratory and pelagic lifestyle of the leatherback turtle makes it extremely difficult to investigate the ecology of this species at sea, which in turn hinders the conservation of this reptile at a global scale. The majority of our knowledge on the leatherback turtle comes from studying them during their reproductive phase when females migrate to tropical areas where they ascend onto beaches to nest.

Credit : Wildlife guide 

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Beluga whales are white whales that live in the Arctic. They attract a lot of attention to themselves because of their unique color and the lack of a dorsal fin. Unfortunately, they are kept in captivity more than any other whale or dolphin species. Due to the irresponsible behavior of humans they are now on the edge of extinction. Belugas are pretty and friendly white whales, and their color helps them to stay alive and protects them from danger. There are many interesting facts about the Belugas that you should know and share with your kids.

Belugas are toothed whales, but they never chew their food. They swallow their prey. Another reason why the Beluga Whale is an endangered species is the fact that they have babies only once in three years. The female Beluga always gives birth to one calf and nurses it until it’s two years of age. The period between conception and birth for Beluga whales is 15 months. So, all in all, a female Beluga can give birth to only one new offspring every three-and-a-half years. The word Beluga comes from the Russian word for white. Although, they are born dark-grey, and it takes eight years for them to turn completely white. Amazing, right? Beluga whales can swim backwards. Beluga whales, just like dolphins, have been known to save people’s’ lives by pushing them to the surface when they are drowning. A captive Beluga saved a free diver’s life in 2009 while she was competing. This fact only confirms how good animals are to us even after all the cruelty they suffer. The Belugas are threatened mostly by being captured for captivity, hunting, climate change, oil and gas development, and industrial pollution. The wild predators that hunt them are Orcas and polar bears. Beluga whales are also known as the canaries of the ocean because of their incredible capability to produce different sounds. Scientists recorded eleven types of sounds that Belugas use to communicate with each other, to identify objects or calculate distance. They have a bulbous structure in their forehead that serves as an echo box where all the sounds come from. High-pitched whistles, clicks, mews, bleats, chirps, and bell-like tones are some of the sounds recognized by scientists. The Beluga’s neck is incredibly flexible and can move up and down and left and right. Such neck flexibility helps the whale to spot their prey easily. Beluga whales living in captivity have been recorded mimicking the human voice. It’s quite amazing to hear them imitating the human voice, but on the other hand, that means they spend so much time surrounded by people in an environment that is not their natural habitat. Beluga whales are highly social creatures that like to communicate with each other and with other species as well. They live in groups called pods, and they travel together everywhere. To spot them in real life, you must visit the Arctic Ocean coastal waters where they spend most of their time. Belugas can live 70 to 80 years, though in captivity they only reach a half of that age. Beluga whales can dive up to 25 minutes non-stop, and reach depths of 2624 feet. The beluga can change the shape of its bulbous forehead, called a “melon”, by blowing air around its sinuses.

Credit : Out door revival

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The ocean is never still. Whether observing from the beach or a boat, we expect to see waves on the horizon. Waves are created by energy passing through water, causing it to move in a circular motion. However, water does not actually travel in waves. Waves transmit energy, not water, across the ocean and if not obstructed by anything, they have the potential to travel across an entire ocean basin.

Waves are most commonly caused by wind. Wind-driven waves, or surface waves, are created by the friction between wind and surface water. As wind blows across the surface of the ocean or a lake, the continual disturbance creates a wave crest. These types of waves are found globally across the open ocean and along the coast.

Credit: National Ocean Service

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Praia do Cassino (Portuguese for Casino Beach) is the longest sea beach in the world and is located in the southernmost of the Brazilian coast, on the South Atlantic Ocean, in the state of Rio Grande do Sul. It is the longest uninterrupted sandy seashore in the world, with various sources measuring it from 212 kilometres (132 mi) to 254 kilometres (158 mi), stretching from the Molhes (breakwaters) at the entrance of the Rio Grande seaport in the north to the mouth of the Chuí Stream, on the border with Uruguay, in the south. Praia do Cassino in Brazil stretches for 241.40 km.

Cassino Beach is known as the oldest spa in Brazil, dating back to 1890. The beach was developed by the Suburban Mangueira Company as a tourist destination. The director of the company, Antonio Condido Sequeira, and the investors of the company acquired the land in the beach area with the help of the state government and built a tourist complex on January 26, 1890. Later this tourist center became very popular and big companies started investing here. At the time, Brazilians of German, English, Portuguese, and Italian descent often came to the beach to enjoy the sea in expensive hotels. The persecution of Italians and Germans during World War II and the ban on roulette in 1948 had a devastating effect on the region’s economy.

The Praia do Casino was recognized as the longest beach in the world by Guinness World Records in 1994.

Around 150,000 tourists visits Praia do Cassino every year. During the summer season, especially from December to January, the number of tourists visiting this place increases. Tourists can be seen participating in various activities including swimming and surfing. This beach is home to the largest number of seals in the world. Many tourists visit these seals by boat.

Credit: Wikipedia

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Canada, the second largest country in the world by total area, is comprised of ten provinces and three territories. Canada also has the longest total coastline among all of the countries of the world. The country’s 202,080 km long coastline fronts on the Pacific Ocean to the west, the Atlantic Ocean to the east, and the Arctic Ocean to the north. Most of the Canadian provinces and territories, with the exception of Alberta and Saskatchewan, have their own respective coastlines. The coastline of the country exhibits varied landscapes across different parts of the country, and most shoreline types are present around the Canadian coastlines, with the exception of such tropical and subtropical ecosystems as mangrove swamps and coral reefs.

Credit: World Atlas

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Only a few fish can adapt to life in the restricted space of a tank, but even these will die if they are not given the right surroundings.

The aquarium must be carefully prepared. On the bottom there should be a mixture of sand and pebbles to give a realistic look. Underwater plants are useful because they help to keep the water pure by absorbing waste products and providing oxygen. The water must be neither too cold nor too warm and it must not contain any harmful substances. It should cover to the aquarium is often used, to reduce evaporation and prevent the fish from jumping out.

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Fishing is one of the oldest activities known to man. Early man who lived on houses erected on poles above the water of lakes, soon learned how to catch the silent creatures that swam around underneath the surrounding waters. The fishing methods of those primitive peoples did not differ much from the lines, nets and hooks of today.

The implements used in fishing can be quite complicated, such as the lobster pots that are sunk, laden with bait, to the sea-bed and the nets which are rigged up by groups of people working together. When these nets are dragged along the water they are known as trawls.

Other types of nets are placed in the water to form a ring which is then gradually closed round the fish and lifted out of the water. This method is known as purse seining. In other netting systems fishermen simply block the fish’s means of escape and force them to swim into a special area where they are caught.

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Did you know the oceans absorb 30% of the CO2 emitted on Earth? At the outset, this might seem like a good thing because it means less carbon dioxide in the air and therefore reduction in global warming. But in the past decades, scientists have realised this comes at the cost of changing the ocean’s chemistry.

When carbon dioxide dissolves in seawater, it forms carbonic acid. When emission increases, a lot of CO2 dissolves in the ocean. Incidentally, the rise in CO2 emission is primarily attributed to human activities. The more the CO2, the more acidic the water gets. Subsequently, the pH level of water goes down. (pH is a measure of how acidic or basic water is.) This process is known as ocean acidification. Ocean acidification has the potential to damage the ocean chemistry. Even a small change in the acidity of seawater can have harmful effects on marine life, impacting chemical communication, reproduction, and growth.

Impact on shelled creatures

Ocean acidification affects ocean species in varying degrees. Creatures such as mussels, clams, urchins, starfish and corals are the worst affected. They make their shells and skeletons by combining calcium and carbonate from seawater. As acidification changes the chemistry of the ocean, these organisms struggle to build their shells and skeletons. Even if they are able to build skeletons in more acidic water, they may have to expend more energy which might otherwise be needed for activities such as reproduction. Further, scientists have found that ocean acidification causes shells of some species to dissolve and slows moulting in crabs and lobsters.

Acidification may also limit coral growth by corroding its skeletons. When reef-building corals are affected, a host of marine life that call the reef their home will also be affected.

Impact on fish

A small change in pH can make a huge difference to survival. In humans, a drop in blood pH level of just 0.2-0.3 can cause seizures, coma, and even death. Similarly, fishes are sensitive to pH. If their blood pH drops, they will have to burn extra energy to get rid of the excess acid in their blood through their gills, kidneys and intestines. This will reduce their ability to carry out other tasks such as hunting, escaping predators and reproducing.

Studies have shown that acidification changes the way sounds get transmitted through the water, making the underwater environment noisier.

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A group of barracudas is called a battery. Barracudas are ferocious, opportunistic predators, relying on surprise and short bursts of speed, up to 43 km/h, to overtake their prey.

Barracuda are snake-like in appearance, with prominent, sharp-edged, fang-like teeth, much like piranha, all of different sizes, set in sockets of their large jaws. They have large, pointed heads with an underbite in many species. Their gill covers have no spines and are covered with small scales. Their two dorsal fins are widely separated, with the anterior fin having five spines, and the posterior fin having one spine and 9 soft rays. The posterior dorsal fin is similar in size to the anal fin and is situated above it. The lateral line is prominent and extends straight from head to tail. The spinous dorsal fin is placed above the pelvic fins and is normally retracted in a groove. The caudal fin is moderately forked with its posterior edged double-curved and is set at the end of a stout peduncle. The pectoral fins are placed low on the sides. Its swim bladder is large. Speedy and dynamic, they are slim, with small scales. Barracudas also have two well-separated dorsal fins, a protruding lower jaw, and a large mouth with many large, sharp teeth.

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The wind is the only thing that propels the sailing boat, so how can a boat sail against it? Amazingly, the most important force that drives a boat into the wind is suction.

The boat’s sail is like an aircraft’s wing on its side. On the outwardly curved, leeward side the wind has to flow around the sail, creating a powerful suction effect pulling the sail towards it. The same principle applies to an aircraft, which gets lift from the suction on the top of its wings.

The suction effect is produced by the laws of aerodynamics. The air that is diverted around a curved sail becomes compressed so that it can squeeze past. When a moving stream of air is compressed its speed increases – a draught under a door can be surprisingly strong for this reason. And when the wind’s speed increases, a lot of pressure occurs. This is because the faster the air is moving, the fewer molecules there are in any given space.

The area of low pressure on the leeward side of sucks that sail towards it with the twice the force that the same strength of wind can push into it on the windward side.

So the wind forces the boat sideways. However, the keel – or centreboard – of the boat resists the sideways movement. The wind’s force is then converted partly into a forward movement of the boat and partly into a tilt to leeward which the yachtsman has to counteract by leaning out from the other side of the boat. The boat sailing close to the wind is bound to move substantially sideways – an effect called leeway. But the helmsman can compensate when plotting his course.

Boat can sail directly into the wind, but at 12 m yacht can sail only 12-15 degrees off the wind. To go in the direction of wind is coming from, the boat has to zigzag, or make a series of tacks. The closer a boat sails to the wind, the slower its speed will be. The helmsman can go faster by making wider zigzags at a bigger angle to the wind, but then he has to travel farther.

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The sinking of them British liner Titanic in 1912, after it collided with an iceberg, spurred scientists to find a means of detecting underwater obstacles. And early form of sound detection was used by British and American forces for submarine detection during the First World War. Modern sonar (sound detection and ranging), which uses the echoes from emitted sounds, was developed by the French scientist Paul Langevin.

Today, echo sounding is used in ship navigation to determine water depth and by fishing vessels to spot shoals of fish, as well as for Marine research and mapping the seabed. Sound pulses, generated electronically, are beamed through the water and echoed back to the ship by any obstacle up to about 6 miles (10 km) away. The returning signals are displayed on a video screen.

Sound travels through water at about 1600yds (1500m) a second – around four times faster than in air. As with radar, the distance to the obstacle is calculated from the time the echo takes to return, and the Doppler shift of the sound waves shows if the object is moving.

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Most of the world’s international telephone conversations are carried by cables laid along the seabed, linking the continents. Communications satellites have not yet removed the need for submarine cables – even the ‘hotline’ between Washington and Moscow uses them. But what happens when a cable fails?

The first transatlantic telegraph cable, laid in 1858, failed within a few weeks. Today the risk of failure has been much reduced by using polythene insulation, and by choosing safer routes that avoid volcanic activity, strong currents and fishing grounds where trawlers may snag their nets on the cables. In shallow sea, cables are often buried.

Despite these precautions, failures still happen. Large telecommunication companies, such as Cable and Wireless, have maintenance ships standing by round-the-clock to carry out repairs.

The job is done by remote-controlled submersibles, as big as a medium-sized van, which are lowered into the water from the maintenance ship, dive to the seabed, locate the fault and attach lines to the surface and repaired on board the ship.

CIRRUS (Cable Installation, Recovery and Repair Underwater Submersible) and it’s even more sophisticated successor ROV128 are controlled through an ‘umbilical’ cable from the ship and powered by hydraulic thrusters.

A submersible’s first job is to find the fault. It follows the line of the cable on the seabed, picking up faint low-frequency signals sent along the cable from the terminal station ashore. If a cable is broken, the water will form a short circuit that will link the individual wires together. When the signal disappears, the submersible settles on the ocean floor and exposes the damaged cable with a powerful jet of water which blows away the layer of sand and silt.

CIRRUS is equipped with powerful lights and television cameras, both colour and black and white, which enable operators on board the ship to see every detail of the seabed. Using the pictures as guidance, the operators extend powerful manipulator arms and grip the cable. CIRRUS uses a special blade to cut the damaged cable, and leaves an acoustic ‘pinger’ on the seabed to mark the spot.

It then rises to the surface, picks up a strong steel line, takes it down to the seabed and clamps it to one end of the cable. The cable is then winched up to the surface. The same process is used to receive the other end of the cable.

Once the cable has been repaired and joined together on board the ship, it is lowered carefully back to the seabed.

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Ever since the 19th century, scientists had tried to invent an effective self-contained breathing device for divers. But if their inventions worked at all, they involved cumbersome diving suits or restricting safety lines. Then in 1943 a French naval captain, Jacques-Yues Cousteau, and his colleague Emile Gagnan, invented the aqualung. Cousteau used the invention to dive to depths of 200ft (60m).

A person’s lungs are not powerful enough to expand against the pressure of water below about 18in (450mm). Water pressure increases rapidly with depth, and at 33ft (10m) it exerts a pressure equal to 2 atmospheres – nearly 30lb per square inch (2 kilos per square centimetre).

To breathe underwater, a diver has to receive air at the same pressure as the surrounding water. This is what the aqualung – or scuba (self-contained underwater breathing apparatus) – provides. Air is stored at high pressure – up to 3000lb per square inch (200 atmospheres) – in cylinders on the diver’s back with a tube to a mouthpiece.

At reaches the diver through a two-stage regulator. The first stage reduces the pressure to about 150lb per square inch (10 atmospheres) above the surrounding water.

The second stage, in the mouthpiece, supplies the diver with air at the same pressure as the surrounding water. A flexible diaphragm in the mouthpiece is open to the water on one side and to an air chamber on the other side. As the diver inhales, the diaphragm is drawn inwards and presses against a lever in the chamber. This opens a valve to let in air from the tube, which drops in pressure as it enters.

When the diver finishes inhaling, the air coming into the chamber pushes against the diaphragm, shutting the valve and cutting off the airflow.

Even when the diver is not inhaling, an increase in water pressure as he dives pushes the diaphragm forward to open the valve and let in air from the tube. So the air in the mouthpiece chamber is always at the same pressure as the surrounding water.

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On the bed of the Atlantic, 2½ miles (4km) down, Dr Robert Ballard saw the bulk of the liner Titanic looming in front of him. He and the crew of the miniature submarine Alvin were the first men to set eyes on the ocean giant since she was sunk by an iceberg nearly 75 years earlier. ‘Directly in front of us was an apparently endless slab of black steel rising out of the bottom – the massive hull of the Titanic,’ he wrote.

Of a second dive – one of nine he made in the Alvin during July 1986 – Dr Ballard recalled: ‘Here I was on the bottom of the ocean, peering at recognizable, man-made artefacts designed and built for another world. I was on the bottom of the ocean, peering at recognizable, man-made artefacts designed and built for another world. I was looking through windows out of which people had once looked, [at] decks along which they had walked, rooms where they had slept, joked, made love. It was like landing on the surface of Mars only to find the remains of an ancient civilization similar to our own.’

The Titanic sank about 450 miles (720km) south of Newfoundland, in the early hours of Monday, April 15, 1912. Of the 2200 people on board, only 705 were saved. It was the liner’s maiden voyage.

But it was not until September 1, 1985 – thanks to modern technological aids – that the wreck was located by a joint French-American expedition, headed by Dr Ballard.

The first step in finding a lost wreck – if it is not found by accident – involves meticulous research in historical archives which should establish as accurately as possible where the vessel went down. Sometimes, this can be quite straightforward.

The Mary Rose, King Henry VIII’s flagship, sank in 1545 in relatively calm waters in the Solent – within sight and hearing of hundreds of people ashore, including the king.

As she sail with a fleet of 60 other warships to confront a French invasion fleet, she heeled in the wind and water poured through her starboard gunports. Her cannons broke their moorings and rolled across the decks, adding their weight to the starboard side. The Mary Rose capsized, drowning 650 men. Her position was known, then lost or forgotten. And it was more than 400 years before she could be raised.

The location of ships that went down in sight of land is usually well documented. The Scilly Isles and Britain’s western approaches harbor at least 400 recorded wrecks and hundreds of unrecorded ones. And an estimated $1 billion worth of gold, silver, jewellery and porcelain lie around the coasts of Florida, the West Indies and Central America.

One of the richest finds was a flotilla of ten Spanish treasure ships off Florida. They set sail for home Havana, Cuba, in July 1715, laden with gold, emeralds, pearls and 2300 chests of newly minted coins from Mexico City – treasure worth at least $50 million in modern currency. The ships were caught in a hurricane and went down south of Cape Canaveral.

During the 1950s, local hotelier Kip Wagner, an avid beachcomber, found a few blackened silver coins in Sebastian Inlet, 40 miles (64km) south of Cape Canaveral. Researching their origin, he read about the fleet – and became convinced he had found some of its treasure. He sent a coin to the Smithsonian Institution in Washington, which told him that it could not be from the fleet, because it had sunk 150 miles (240km) farther south.

Undeterred, Wagner and a friend, Dr Kip Kelso, continued their own research and found that Bernard Romans, an English mapmaker, in 1775 had described the place where the fleet went down and had even drawn a map. Armed with a secondhand mine detector, Wagner searched the beaches near the area described – and found a huge hoard of valuables, including a gold chain and pendant, auctioned for $50,000, and a diamond ring worth $20,000.

Wagner put to sea and began to dive up find the wrecks. The treasure he ultimately recovered was worth more than $5 million.

Wagner’s use of a mine detector triggered the use of modern technology in the search for wrecks. In 1970, Rex Cowan, a London solicitor, decided to search for a Dutch East Indiaman, the Hollandia, lost off the Scilly Isles in 1743. He knew from contemporary accounts roughly where the wreck might be, but divers could find no trace. Cowan used a magnetometer – an instrument towed behind a ship which detects anomalies in the magnetic field caused by iron objects such as cannons.

After months of crisscrossing the likely area in a grid pattern, Cowan and his team finally got a reading only a few days before the end of the diving season in September, after which weather conditions tend to be unfavorable. They went below, found nothing, but returned the next day – and discovered cannons bearing the monograph of the Amsterdam chapter of the Dutch East India Company. Next they discovered a silver spoon bearing the crest of a Dutch family, the Imhoff-Bentincks, one of whose members was known to have been aboard the Hollandia, confirming the source. Ultimately, more than 35,000 silver coins, worth around £1 million, were found.

Magnetometers proved unsuccessful, however, in rediscovering the Mary Rose. Although she had sunk only a few hundred yards from the shore, she was covered by mud and sand when the search for the wreck began. A magnetometer found a buried cable not recorded on Admiralty charts – but no wreck.

The breakthrough came from another modern invention – sonar. Developed for underwater warfare, sonar sends out sound signals and records the echoes as they are reflected off solid objects.

A type of sonar called a sub-bottom profiler, which can detect objects embedded in mud or sand, produced signals suggesting the presence of a mound on the seabed – and something solid beneath. Three years later, tides had removed some of the silt from the port side of the wreck and timbers could be seen. Then began the historic recovery and the painstaking recording of its contents – a unique time capsule of life aboard a medieval man-of-war.

But the rediscovery of the Titanic must rank as the most remarkable deep-sea find. It lies too deep for divers and finding it in the immensity of the North Atlantic with only a rough idea of where it lay called for special skill. The joint French-US team used a deep-sea sonar device to search the ocean floor and find the wreck – then a remote-control underwater camera to take the first pictures. A year later, Dr Ballard, a marine geologist from the Woods Hole Oceanographic Institute, Massachusetts, saw the wreck for himself, from the three-man submarine Alvin.

The submarine landed on the bow and the bridge. A remote-control underwater robot camera. Jason Junior, described the Grand Staircase, photographing still-hanging chandeliers, clocks, silverware, and the interiors of staterooms.

With such techniques, few wrecks anywhere beneath the Earth’s oceans are beyond man’s reach. If they are worth investigating mankind now possesses the technology.

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Here are the twelve incredible facts about jellyfish:

1. Jellyfish are invertebrates, that is, they have no spinal cord (the backbone that helps us sit up).
2. Jellyfish have no brains – they have no hearts or eyes. Yet, they have been around in the seas for over 500 million years since history began to be recorded. In all these years, the shape of the jellyfish has hardly changed. They still strongly resemble their ancestors from 500 million years ago. Remarkable!
3. The box jellyfish is considered the most vermous marine animal in the world. It has a cube-shaped body. Its tentacles are covered in poison-filled darts. Some of these box jellyfish have venom that can kill humans. Anyone stung by one of them can go into cardiac arrest or die within minutes.
4. Jellyfish are mostly water. About 5% of jellyfish bodies are made of structural proteins, muscles and nerve cells, while the remaining 95% is water. Human bodies, by comparison, are up to 60% water.
5. Groups of animals are usually given a collective noun as a name. A group of cows is a herd, for example, while many fish swimming together form a “school.” Jellyfish groups can go by three different names. A collection of jellyfish is called a “bloom,” “smack,” or “swarm.” Which other group is called a “swarm”?
6. Jellyfish are not classified as a variety of fish. Fish are vertebrates that live in water and breathe through their gills. Jellyfish, on the other hand, are invertebrates, meaning they have no backbone and they absorb oxygen from water through membranes.
7. In 1991, over 2,000 jellyfish polyps were blasted into space to test how they reacted to the lack of gravity. Those jellyfish reproduced in space, creating over 60,000 jellies, but the space-bred jellies weren’t able to function.
8. While some are poisonous, jellyfish can be a delicacy. There are some 25 edible types of jellyfish. They’re typically added to salads or are pickled. As raw fish, they have a salty taste and the consistency of noodles.
9. One type of jellyfish is described as immortal. The Turritopis dohrnii jellyfish is thought to be immortal, since it can turn into a colony of polyps (individual organisms). As the jellyfish grows old, it settles on the sea floor and becomes polyps. The polyps then give birth to new, genetically identical jellyfish.
10. Jelyfish tend to follow the currents of the ocean as they move. So they can be found around the world in every type of ocean water. They can thrive in warm tropical water or cold Arctic water. They’ve been found at the bottom of the ocean and near the surface.
11. Since jellyfish don’t have any bones, it is difficult to find fossils of ancient jellies. But in 2007, a preserved jellyfish fossil was discovered in Utah that’s thought to be over 505 million years old. Dinosaurs lived from about 245 million to 66 million years ago, meaning jellyfish pre-date them by at least 250 million years.
12. Bioluminescence is the term for  creature’s ability to produce its own light. Some jellyfish have this and produce an internal glow.

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In July, 2019, two divers were swimming off the south-western tip of England. They hoped to see some rare fish, but what they came across blew their mind away. Crossing their water-path was a huge hulk of a barrel-jellyfish (Rhizostoma pulmo). The giant jellyfish was the size of a human being. It is a rarely seen species. Luckily, the divers – biologist Lizzie Daly and underwater cinematographer Dan Abbott – managed to film the mammoth creature.

The divers then shared the encounter in a Facebook video they posted on July 13. This was the time when Britain was running the Wild Ocean Week campaign to raise funds for the United Kingdom’s Marine Conservation Society. People has been invited to present pictures of any strange creatures underwater.

The divers actually saw the giant jellyfish emerge from the murky water. The fish is also called the dustbin-lid jellyfish. It is characterized by eight thick arms ending in tentacles. Its head is large and rounded. Put together, these features make it look like the lid of a garbage bin. Barrel jellyfish sometimes wash up on the shore.

The largest

Is the barrel jellyfish the largest of the species? No. That award goes to the lion’s mane jellyfish (Cyanea capillata), the largest known species in the world. This coldwater jellyfish has 1,200 long, trailing tentacles. If you measure the length of the tentacle, an individual lion’s mane jellyfish can be as long as 120 feet (36.5 metres). The tentacles of a lion’s mane can sting 50 to 100 people in just a few minutes if it is let loose among a crowd. Most encounters cause temporary pain and localized redness.

On a July day in 2010, around 150 beach-goers at Wallis Sands State beach in New Hampshire in the U.S. were study by the remains of a lion’s mane jellyfish that had broken up into countless pieces. Thankfully it caused temporary pain and redness around the area of the sting.

The smallest

The smallest of the species is called Irukandji (Malo maxima). It is 1 mm long and 5 mm across the part that looks like a lid. Box Jellyfish (Chironex fleckeri) is the most venomous. It is found in the Australian coasts and is considered the most poisonous, deadliest and meanest of all the jellyfish. The variety of box jellyfish known as the sea-wasp or marine-stinger has been declared one of the most deadly creatures on Earth.

Their food

What do they eat normally? Jellyfish typically eat small plants, shrimp, or fish. They use their tentacles to stun prey before eating it. According to the Mayo Clinic, if you find yourself stung by a jellyfish, your best course of action is to remove any tentacles carefully with tweezers and soak the area in hot water. If a person gets a severe reaction or becomes unconscious after a sting, seek medical attention immediately.

Picture Credit : Google