My Science School

Over the last few years, you may have come across several news reports on how coral reefs the world over are suffering. Come, let's find out what affects these coral reefs, and how this has an impact on humans too.

What are coral reefs?

Corals are marine invertebrates living in colonies. They take calcium carbonate from the seawater and make hard exoskeletons to protect their "soft, sac-like bodies". They use the exoskeleton of their ancestors while adding new layers to it. So, over a period of time as the new layers keep getting added, it forms large underwater structures called coral reefs. Each individual coral is referred to as a polyp. Most corals have a symbiotic relationship with an algae called zooxanthellae. They live in the coral polyp's body, and through photosynthesis, provide energy for themselves and the polyp. They also give corals their spectacular colours. Without these algae, the corals are colourless.

What is killing the coral reefs?

Coral reefs are found in all the oceans. When ocean waters warm, the corals expel the algae and return to their colourless selves. This is called coral bleaching. If oceans keep warming, the corals will not allow the algae to return, and will eventually die. A recent study by the Global Coral Reef Monitoring Network, a United Nations supported global data network, said the world's coral reefs will disappear if oceans keep warming. Coral reefs are important to several marine creatures because they provide shelter, are spawning grounds, and offer them protection from predators. So, when coral reefs die, it affects several living organisms. Not just that, they have a bearing on humans too.

Impact on humans

As natural barriers, coral reefs take the impact of waves and storm surges, and help coastal communities stay safe. Further, when coral reefs die, they cannot support marine organisms anymore, so many of those species die too. These include a variety of fish, crabs, shrimps, etc., which are consumed by humans. While the livelihoods of fishing communities are affected by the lack of such sea food, people consuming these are forced to look for other food options, which could cause an imbalance in food sources. Another important aspect is tourism. Tourism brings in plenty of money and supports several jobs directly and indirectly related to the reefs. When the reefs go, so will tourists and the money they bring in.

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Naval Base Kitsap is a U.S. Navy base located on the Kitsap Peninsula in Washington state, created in 2004 by merging the former Naval Station Bremerton with Naval Submarine Base Bangor. It is the home base for the Navy’s fleet throughout West Puget Sound, provides base operating services, support for both surface ships and fleet ballistic missile and other nuclear submarines as one of the U.S. Navy's four nuclear shipyards, one of two strategic nuclear weapons facilities, and the only West Coast dry dock capable of handling a Nimitz-class aircraft carrier and the Navy's largest fuel depot. Naval Base Kitsap is the third-largest Navy base in the U.S.

 It also provides service, programs, and facilities for their hosted combat commands, tenant activities, ships' crews, and civilian employees. It is the largest naval organization in Navy Region Northwest, and composed of installations at Bremerton, Bangor, Indian Island, Manchester, and Keyport, Washington. It received the 2005 and 2017 Commander in Chief's Award for Installation Excellence - the Best Base in the U.S. Navy.

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The Navy's Marine Mammal Program began in 1960 with two goals. First, the Navy wanted to study the underwater sonar capabilities of dolphins and beluga whales to learn how to design more efficient methods of detecting objects underwater, and to improve the speed of their boats and submarines by researching how dolphins are able to swim so fast and dive so deep. In addition to this research component, the Navy also trained dolphins, beluga whales, sea lions and other marine mammals to perform various underwater tasks, including delivering equipment to divers underwater, locating and retrieving lost objects, guarding boats and submarines, and doing underwater surveillance using a camera held in their mouths. Dolphins were used for some of these tasks in the Vietnam War and in the Persian Gulf. The Marine Mammal Program was originally classified, and was at its peak during the Cold War. The Soviet Union's military was conducting similar research and training programs in the race to dominate the underwater front. At one point during the 1980's, the U.S. program had over 100 dolphins, as well as numerous sea lions and beluga whales, and an operating budget of $8 million dollars. By the 1990's, however, the Cold War was over, and the Navy's Marine Mammal project was downsized. In 1992, the program became declassified. Many of the dolphins were retired, and controversy arose over whether or not it would be feasible to return unnecessary dolphins to the wild.

Credit : Frontline

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While bull sharks are commonly found along coastlines, bays, and harbors, they also frequent a most uncommon shark habitat—freshwater rivers.

The species has been spotted 2,500 miles (4,000 kilometers) up the Amazon River in South America and dwell in Lake Nicaragua, a freshwater lake in Central America. Bull sharks have traveled up the Mississippi River as far north as Illinois and are regularly spotted in India's Ganges.

Their ability to tolerate freshwater is rooted in salt retention.

Sharks must retain salt inside their bodies. Without it, their cells will rupture and cause bloating and death. Given this requirement, most sharks cannot enter fresh water, because their internal salt levels would become diluted.

But bull sharks have special physiological adaptations that enable them to live in fresh water. Their kidneys recycle the salt within their bodies and special glands, located near their tails, also aid in salt retention.

While scientists have learned how the animals survive in fresh water, it is less clear why bull sharks, almost exclusively, developed this amazing ability.

Heithaus, of Florida International University, speculates that "probably the biggest reason is that [freshwater tolerance] allows the juveniles, the little guys, to be in a place that's relatively safe from being eaten by other sharks."

Adult bull sharks likely gain their own competitive advantages from salt retention. However, scientists have yet to uncover precisely what those advantages may be.

Heithaus said a big question for him is what bull sharks gave up to acquire their unique ability to survive in fresh water. "If they were a master of all trades, in both fresh and saltwater, we should see bull sharks dominating coastal waters," the marine biologist said. "There must be some cost to having that amazing ability."

Freshwater tolerance could be rooted in competition for saltwater food resources, where perhaps bull sharks suffered and needed to develop an edge. The ability might also be tied to disease susceptibility or other unknown and unstudied issues.

Credit : National Geographic

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Leatherback sea turtles are the biggest turtles on Earth. An adult leatherback sea turtle is generally longer than an average-size man is tall. Unlike other species of sea turtles, which have hard shells, the leatherback's shell is leathery; it feels almost rubbery. The shell is black, often speckled with white or yellow spots. These huge reptiles lived 100 million years ago—during the age of dinosaurs—but their future is uncertain.

Leatherbacks are one of the more endangered creatures on Earth. They are often caught by accident in fishing nets. Stuck underwater, they drown. Sea turtle nesting habitats are also being destroyed, and the eggs they do lay are illegally collected by people for food.

Newly hatched sea turtles instinctively head from the nest to the sea, but in areas where people live, the hatchlings often become confused by lights from houses built along shore. Instead of heading to sea, they head toward the lights. Another hazard for sea turtles is floating plastic trash, which they often mistake for jellyfish, their main food. Leatherbacks must breathe air at the surface, but can stay underwater for up to 35 minutes at a time. Only females ever leave the ocean.

During nesting season, the female comes ashore on a sandy beach, where she digs a hole. She lays about 100 eggs in the hole, covers them with sand, and heads back to sea. Sea turtles do not guard their nests, so the babies are on their own. The eggs take about two months to hatch. The tiny hatchlings are only 2 to 3 inches (5 to 8 centimeters) long.

As soon as they hatch, they dig their way out of the sandy nest and scurry across the beach to the sea. Gulls and other birds often scoop up the hatchlings before they make it to the water. Other predators, such as large fish, await those lucky enough to make it into the sea.

Credit : National Geographic 

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Jellyfish have been around for millions of years and live in oceans all over the world. There are many different types of jellyfish. Some just look like small, clear blobs, while others are bigger and more colorful with tentacles hanging beneath them.

It's the tentacles that sting. Jellyfish sting their prey with them, releasing a venom that paralyzes their targets. Jellyfish don't go after humans, but someone who swims up against or touches one — or even steps on a dead one — can be stung all the same.

While jellyfish stings are painful, most are not emergencies. Expect pain, red marks, itching, numbness, or tingling with a typical sting.

But stings from some types of jellyfish — such as the box jellyfish (also called sea wasp) — are very dangerous, and can even be deadly. These jellyfish are most often found in Australia, the Philippines, the Indian Ocean, and central Pacific Ocean.

Jellyfish stings leave thousands of very tiny stingers called nematocysts in the skin. These stingers can continue to release (or "fire") jellyfish venom (poison) into the body.

It's best to rinse a sting with vinegar. Vinegar is a weak acid that might keep the stingers from firing for some kinds of stings (especially from dangerous types like box jellyfish). Rinsing with cool fresh water can make more stingers fire. Also, rinsing a sting with seawater had been thought to prevent them from releasing more venom. But now, some experts say that can actually make a sting worse.

Also, do not scrape off any stingers still in the skin. This also used to be recommended, but now is thought to make stings worse.

Credit :  KidsHealth 

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Seahorses can change color, move their eyes independently of one another, and even have prehensile tails (like monkeys). The fact that male seahorses also get pregnant and give birth is sure to leave you in total awe of these fascinating fish!

While we celebrate all the scuba diving, freediving, and ocean-loving dads out there, we also want to give a big shout out to the most unique dads that call the underwater world home. In the entire animal kingdom, male seahorses (and their close relatives) are the only male animals that undergo pregnancy and give birth to offspring.

Although male seahorses carry the eggs, they don’t make them. After the male and female seahorses spend time courting, the female deposits her eggs inside the male’s pouch. The male then fertilizes the eggs inside the pouch. Instead of growing their babies inside a uterus like human moms do, seahorse dads carry their babies in a pouch. Their pouch provides oxygen and nutrients, as well as regulates temperature, blood flow, and salinity for the developing eggs.

Depending on the species, male seahorses typically carry their eggs for 2 -4 weeks. Then, they give birth to 100 – 1,000 babies at a time. That’s a lot of adorable, teeny tiny seahorses! Like human moms, seahorse dads give birth through energetically costly muscular contractions.

Credit : PADI

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Piranhas can make different sounds, especially when they’re feeling afraid or defensive. They may bark, grunt or make thudding or drumming sounds. To do this, they use their swimbladder, an organ most fish have that helps them float in water.

Piranhas live in groups called schools or shoals. Usually a shoal has about 20 individuals but sometimes can have over 100. Swimming together helps keep the fish safe from predators, including larger fish, crocodiles, birds and mammals like jaguars and humans. Piranhas spend most of their day hiding and looking for food.

Piranhas eat smaller fish and nips of other fish’s tails, bugs and worms, crustaceans and carrion (dead meat). Some are omnivorous, eating plants and seeds as well as meat, and one species in Brazil is reported to only eat river weeds. These fish help maintain healthy ecosystems as both predators and scavengers.

Red bellied piranhas are known to be carnivorous and hunt in packs. They can smell and sense movement. At Berkshire Museum, they eat worms and frozen fish called smelt. If one of the piranha in pack is weak or sick, the others will eat it.

Credit : Aquarium Facts

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Dolphins also communicate through a series of clicking sounds and whistles, each with their own unique vocal pitch. These differences in vocal pitch are essential to communicating within the pod so dolphins can decipher who’s speaking.  

Beyond echolocation, clicking and whistling, dolphins communicate with a variety of body language signals including tail and flipper slapping on water, leaping out of water, bumping each other and spy hopping. Depending on the hardness and repetition, tail and flipper slaps can serve as a warning to other dolphins of nearby danger, or be a sign of playful communication. Dolphins can also use their tail and flipper slaps to indicate specific desires, if they’re hungry or if they simply want to play.

Sky hopping is when a dolphin pokes their head above the surface of the water for an extended period of time to survey their surroundings. It’s believed dolphins use this technique to keep an eye out for predators.

Dolphins also communicate through physical contact. Hard bumping with the head and charging are aggressive signals dolphins use to ward off competing males during mating periods. On the other fin, gentle bumping and touching are signs of affection.

Credit : Discovery Cove

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Coral reefs are some of the most diverse ecosystems in the world. Coral polyps, the animals primarily responsible for building reefs, can take many forms: large reef building colonies, graceful flowing fans, and even small, solitary organisms. Thousands of species of corals have been discovered; some live in warm, shallow, tropical seas and others in the cold, dark depths of the ocean.

Shallow water, reef-building corals have a symbiotic relationship with photosynthetic algae called zooxanthellae, which live in their tissues. The coral provides a protected environment and the compounds zooxanthellae need for photosynthesis. In return, the algae produce carbohydrates that the coral uses for food, as well as oxygen. The algae also help the coral remove waste. Since both partners benefit from association, this type of symbiosis is called mutualism.

Deep-sea corals live in much deeper or colder oceanic waters and lack zooxanthellae. Unlike their shallow water relatives, which rely heavily on photosynthesis to produce food, deep sea corals take in plankton and organic matter for much of their energy needs.

Unfortunately, coral reef ecosystems are severely threatened. Some threats are natural, such as diseases, predators, and storms. Other threats are caused by people, including pollution, sedimentation, unsustainable fishing practices, and climate change, which is raising ocean temperatures and causing ocean acidification. Many of these threats can stress corals, leading to coral bleaching and possible death, while others cause physical damage to these delicate ecosystems. During the 2014-2017 coral bleaching event, unusually warm waters (partially associated with a strong El Niño) affected 70% of coral reef ecosystems worldwide. Some areas were hit particularly hard, like the Great Barrier Reef in Australia, where hundreds of miles of coral were bleached.

Corals are able to recover from bleaching events if conditions improve before they die, though it can take many years for the ecosystems to fully heal. Scientists are also testing new ways to help coral reef ecosystems, such as growing coral in a nursery and then transplanting it to damaged areas.

Credit : National Oceanic and Atmospheric Administration

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Dolphins are able to protect vulnerable members of their pods and extended families such as young dolphins and injured or sick dolphins. Dolphins use their strong snouts as a powerful weapon to ram sharks, targeting their soft underbellies and gills to cause injuries.

Sharks pose less of a threat to larger members of the dolphin family. Indeed, orcas are the top predator in the ocean and small sharks are a target for some populations. Orcas will even attack and kill great white sharks just to eat their livers which are a high energy food source.

When dolphins are hungry, they turn into calculating predators who are capable of developing unusual methods to trap their prey. For instance, dolphins that live in the shallow waters of Florida have been observed using their tails to kick up mud in a circular formation in order to trap fish inside, while dolphins who live in Shark Bay, Australia, have been seen using sponges as tools to dig up prey from the seafloor.

What's more, dolphins are able to communicate these tactics with other dolphins, which means they're always improving their skills. According to the Smithsonian, "dolphins learn different tricks for catching food from one another in a kind of cultural transmission."

Dolphins have sharp teeth that they usually use to rip apart their prey. Bottlenose dolphins, for example, have between 80 and 100 teeth that they use to grab, grip and secure their prey.

However, the creatures can (and do!) bite humans on occasion. Because of the potential danger, officials at the Commerce Department's National Marine Fisheries Service have even released fliers with warnings that "dozens of bites have been reported" and "people have been pulled underwater" by the animals. In fact, as recently as 2012, an 8-year-old girl was infamously bitten by one of the animals at SeaWorld.

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The giant Pacific octopus grows bigger and lives longer than any other octopus species. The size record is held by a specimen that was 30 feet across and weighed more than 600 pounds. Averages are more like 16 feet and 110 lbs.

They hunt at night, surviving primarily on shrimp, clams, lobsters, and fish, but have been known to attack and eat sharks as well as birds, using their sharp, beaklike mouths to puncture and tear flesh. They range throughout the temperate waters of the Pacific, from southern California to Alaska, west to the Aleutian Islands and Japan.

Highly intelligent creatures, giant Pacific octopuses have learned to open jars, mimic other octopuses, and solve mazes in lab tests. Their population numbers are unknown, and they do not currently appear on any lists of endangered or vulnerable animals. However, they are sensitive to environmental conditions and may be suffering from high pollution levels in their range.

Credit : National Geographic

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The Irukandji jellyfish found off the northern coast of Australia is one of the most venomous species of jellyfish in the world. No bigger than your fingernail, it has stingers on its tentacles as well as on its bell. It can fire stingers to inject venom into its prey. Its stings are said to cause fatal brain haemorrhages.

The Irukanji syndrome was named in 1952 by Hugo Flecker, who first described the symptoms of this jellyfish envenoming. The syndrome were named after the Irukandji people, whose country stretches along the coastal strip north of Cairns, Queensland. The first of these jellyfish, Carukia barnesi, was identified in 1964 by Jack Barnes; to prove it was the cause of Irukanji syndrome, he captured the tiny jellyfish and allowed it to sting him, his nine-year-old son and a robust young lifeguard. They all became seriously ill, but survived. Australian toxicologist Jamie Seymour made a documentary about the jellyfish called Killer Jellyfish

The Irukanji jellyfish exists in the northern waters of Australia. The southern extent of the Irukanji's range on Australia's eastern coast has been gradually moving south.

There has been an increased incidence of Irukanji stings reported around Great Palm Island, off the coast of north Queensland near Townsville. By early December 2020, the number of stings reported, at 23, was nearly double that of the whole of 2019, at 12.

Some are believed to have spread farther north as symptoms of the species have been experienced off the coasts of Florida, Japan and Britain.

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Vaquita is a small porpoise, found only in the Gulf of California, in Mexico. Its body is grey, olive and stocky, with a blunt head and no beak. Eyes are encircled with black rings. It has small spade-shaped teeth.

It feeds on a variety of benthic fishes, squids, and crustaceans. It uses echo-location to move and hunt and high-pitched clicks to communicate with fellow vaquitas.

It is a critically endangered species. Its biggest threats are bycatch, chemical pollution of water and climate change that decreases availability food.

Vaquita often are caught in nets set to catch other animals. This "incidental take" is the primary reason for the vaquita's endangered status. Gulf of California fisheries include shrimp trawling and gillnet fisheries for sharks. (A gillnet is a large flat fishing net that entangles fish as it hangs vertically in the water.) Each year, 25 to 30 vaquita drown in gillnets.

Vaquita survival is closely related to the totoaba (Totoaba macdonaldi,) fishery. Like the vaquita, the totoaba lives only in the northern Gulf of California. Vaquita are easily entangled in the larger holes of the totoaba nets. In 1990, the International Whaling Commission (IWC) determined that the totoaba fishery is responsible for the vaquita's endangered status.

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