My Science School

A blue whale is the largest known animal, found in oceans around the world, except the Arctic.

It grows up to 110 feet in length and 150 tonnes in weight. Did you know its tongue alone can weigh as much as an elephant?

Its diet consists exclusively of krill, which are tiny shrimp-like creatures. It eats tonnes of them at times.

They spend summers feeding in polar waters and undertake long migrations towards the Equator as winter arrives.

It makes a range of sounds to communicate and navigate. It is among the loudest animals on the planet.

These marine marvels are a species of ‘baleen’ whale. Instead of teeth, they have baleen, a fibrous material used to filter their food. When eating, the whale lets a huge volume of water and krill into its mouth. It then pushes the water through its 300-400 baleen plates, which trap the tasty grub to be swallowed. Gulp!

Sadly, in the late 19th early 20th century, blue whales were heavily hunted. And despite a global hunting ban in 1966, their population has declined by 70-90 percent in the past 150 years. With only 10,000-25,000 left in the wild, these magnificence marine mammals are today classified as an endangered species.

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The shipping industry is among the biggest polluters in the world. It emits around 940 million tonnes of CO2 annually and is responsible for about 2.5% of global greenhouse gas emissions. Emissions, especially those of carbon dioxide, are directly proportional to fuel consumption. And shipping industry encounters an unusual problem in the form of marine biofouling which further contributes to its fuel consumption.

The marine biological fouling is the accumulation of undesirable marine organisms, including microbes plants, algae, and animals, on an immersed surface in seawater. This can be seawater cooling systems, platforms, buoys, underwater cables, oil installations, offshore structures and underwater acoustics instruments. In the case of ships, this accumulation usually happens on their hull. More than 4,000 marine species have been identified as biofouling organisms. Biofouling is divided into microfouling biofilm formation and bacterial adhesion - and macrofouling-attachment of larger organisms.

The surface-liquid interface such as the one between the ship's hull and water favours an ideal environment for attachment and growth of micro organisms. Once attached, the microbes quickly establish a slimelike coating and multiply. Among macrofouling organisms, barnacles are arguably the most troublesome, in part because the hundreds of different species colonise a wide variety of marine surfaces, ranging from rocks and docks to whale fins. Barnacles are filter feeders. They benefit from a constant flow of water around them. They settle in an area with pronounced water movement or settle on a moving substrate such as a ship. They secrete a fast curing cement that is among the most powerful natural glues known. The glue is so strong that researchers are still figuring out ways to detach them from ships and other surfaces.

A cause for concern

• Accumulation of large colonies of barnacles for instance can increase the weight of the ships and cause them to drag and burn more fuel, leading to significant economic and environmental costs. These organisms may lead to decrease of speed by up to 10%, something that in turn may require even a 40% increase in fuel to counterbalance.
• Another major concern over biofouling is the spread of invasive aquatic species to new environments by ships. They may survive to establish a reproductive population in the host environment, becoming invasive, out-competing native species and multiplying into pest proportions. This problem has become more evident the last decades, as shipping traffic in the oceans has increased greatly.

Solution

The shipping industry employs a process called antifouling, which is a way to protect a ship's hull with specifically designed materials, such as special paints, that prevent these organisms from piling up. But this is an expensive process and do not always work. Scientists are looking to employ robotics technology to clean the ship's hull and prevent the build-up of fouling. The robotic cleaners can be used every time the vessel is anchored.

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You may have watched videos of dolphins gliding quickly and smoothly in the water. Any idea how they do it? The answer could be in their skin. Come, let's find out how exactly their skin helps dolphins swim well. Like fish, dolphins too have streamlined bodies. A streamlined body is shaped in such a way that it reduces resistance between a fluid and an object moving through that fluid. The fluid can be air or water, and the object could be anything from fish to birds. In this case, it's water and the mammal dolphin. The dolphin does not have hands or legs sticking out to slow it down while it swims in the water. Further it has skin that is devoid of hair. These also help the dolphin gather speed in water. But there's something even more interesting at play.

Dolphins shed skin. That by itself is not unusual considering humans do it too. But dolphins shed skin once every two hours that's a whopping 12 times every single day! To understand how the soft and flaky skin worked in the dolphin's favour, researchers from Japan devised a computer simulation, for a study many years ago. It modelled how water flowed over dolphin skin, representing every individual flake and the way it peeled off. The scientists discovered that "the 'softness or waviness of the skin helped reduce friction". They also found out that shedding skin reduced the friction by "disturbing tiny whirlpools of water" around a dolphin's body and "impact their gliding".

Despite shedding skin so often, dolphins are not immune to skin diseases. Since they're always wet, they do not have skin dryness. However, changes in salinity or the temperature of water can increase microbe production, leading to skin infection. Stranding is another aspect of concern because the sun can burn their skin.

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Big Major Cay, an island in Exuma, the Bahamas, has a rather than unusual attraction – the swimming pigs. Also known as Pig Beach, the island is about 82 miles south-east of Nassau. It is inhabited by feral but friendly swimming pigs that paddle around in the beautiful blue green water of the Bahamas.

The swimming pigs have populated the island for decades, but their actual origin is somewhat of a mystery. Local legend claims that they swam ashore after a shipwreck or were left on the island by sailors who planned to come back and eat them, but never returned. Today, the colony of these feral pigs has become a tourist attraction. Tourist can drive up to the pigs, and it’s legal for tourists to swim with them. Other islands of the Bahamas too have swimming pigs but not exclusively of them.

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In the wild, several species of birds and animals move from one region to another– some of them even cross continents. This temporary movement is called migration, and there are many reasons behind this. It could be to find a breeding ground, to find food, or even to escape the extreme weather in the region they inhabit. For migrating species, this movement is a regular process, and is crucial in keeping themselves and their species alive. However, studies have shown that climate change could be impacting migration. For instance, according to a 2019 study in the US, “Rising temperatures are causing birds to migrate a little earlier each spring“. It discovered that their journey home is getting advanced by about two days each decade. Another recent study has shown that bowhead whales completely skipped migration a couple of years ago. Why did they do it, and how was this discovered?

What happened?

Bowhead whales reside completely in the Arctic and sub-Arctic waters, and requires temperature between -0.5 and 2°C to thrive. There are different groups of bowhead whales in the Arctic. One group – what about 20,000 whales – travels every year from the Bering Sea via the Chukchi Sea In spring to the Beaufort Sea to spend the summer there. The population returns to the Bering sea in autumn, and stays there in winter. And the cycle continues. But then, Researchers in Canada discovered that this population did not take up the usual 6000-km round trip in 2018–2019 after spending the summer in the Beaufort Sea, the population had remained there during the winter instead of heading to the Bering sea.

Why?

Scientists have considered several reasons for this. One of the important reasons is that warming waters had led to less ice cover during the season. Since this usually helps in the large-scale movement of the bowhead whales’ predator orca or killer whales, it is assumed that bowhead whales stayed where they were due to “predator avoidance”. Another reason suspected is the erratic and early bloom of plankton in the region, a key food source which the bow head whales could have hoped to feast on. Yet another suggestion is that due to warming temperatures, the water in their migration route could have fallen outside their ideal temperature range, and so the whales must have decided to skip on the journey altogether. Whatever their reasons, it seems likely that climate change has had an important role to play in their unusual behaviour.

How was this discovered?

The researchers in Canada went through several hours of audio recordings captured by underwater devices used for regular data collection. And then they discovered the distinctive calls of the bowhead whales, which should have been in their wintering grounds. As one media report says, “Eerie wails, explosive trumpets and ghostly moans. The sounds from the underwater recorders had a story to tell, even without a single intelligible word: the whales had stayed put.”

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Stretching over 2,000 km in the Pacific Ocean along the coast of Queensland in Australia, it’s small wonder that the Great Barrier Reef is the largest living structure on Earth and home to the world’s largest coral reef. Visible even from Space, it comprises nearly 3,000 individual reefs in different shapes and sizes, in addition to several hundred islands nurturing a starting variety of plants and animals. In 1981, the region was included in UNESCO’s World Heritage List for its “outstanding natural universal values”.

Marine life

The Great Barrier Reef hosts over 400 types of coral, 1,500 species of fish, 5,000 types of molluscs, and 200 species of birds. Thanks to the extraordinary diversity in terms of habitats and species, the reef is one of the most complex natural ecosystems in the world. It is home to a staggering number of marine creatures. As if a fittibg underwater competitor to Africa’s Big Five, it houses the Great Eight – clown fish, sharks, manta rays, Maori wrasse, potato cod, giant clams, turtles, and whales. The reef is considered one of the best places to spot sea turtle species of the world are found here. The region holds scientific significance for being the habitat of the much threatened dugong (sea cow).

Did you know?

• Over the last few decades, global warming has resulted in coral bleaching in the Great Barrier Reef. An aerial survey revealed that back-to-back unprecedented coral bleaching in 2016 and 2017 affected nearly two-thirds of the corals, giving the damaged ones little chance to recover. In 2020, the region experienced what was reported as the “third mass coral bleaching event in five years”. However, some good news came in later.
• A survey was carried out in several parts of the region in 2020. Though most of the places were subject to various levels of bleaching, the overall bleaching was ascertained to be mild. The best news was that “many species were in recovery and mortality was extremely low”. The survey also conducted that “if conditions become more favouarble quickly there is a strong chance they will recover.
• There’s still a lot we do not know about the Great Barrier Reef, and it continues to awe and surprise us regularly. It did just that last year too. Explorers of the region discovered a giant pinnacle of coral taller than the Empire State Building in New York, the U.S. Considered the first such discovery in more than a century, the coral stood at 500 mt. For scale and comparison, the Empire State Building – one of the tallest buildings of the world – is not even 450 mt.

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A deadly bloom has hit Chile, where more than 4,200 tonnes of fish have been killed. It’s the latest mass mortality event recorded in Chile, the second largest salmon producer after Norway.

Some 18 salmon farms in the south of Chile, which produces around 26% of the world’s salmon, have been affected.

Scientists attribute the die-off to algal blooms that reduce the amount of oxygen in water, thus suffocating the salmon. The same phenomenon killed thousands of tones of salmon in 2016.

Greenpeace, the international environmental organisation, says the algal bloom is due to pollution caused by salmon farming. Emission of ammonium and urea from salmon farms into closed fjords or with little circulation can exacerbate blooms, it points out.

What is algal bloom?

When the normally occurring aquatic algae reproduce faster and grow out of control, it is called algal bloom. It may turn waterbodies orange, yellow, brown or purple depending on the algae species in question. Some of the blooms have the potential to be harmful.

Combination of factors

The blooms are caused by a combination of factors: high concentrations of nutrients that feed algae, warm temperatures, sunlight and shallow, slow-flowing water.

When humans channel agricultural runoff, sewage and industrial effluents into waterways, the amount of nutrients in the water increases. the excess nutrients, especially nitrogen and phosphorous, lead to a spurt in the growth of microscopic algae called phytoplankton.

Algal bloom often happens during the warm summer season or when water temperatures are warmer than usual. Warmer temperatures make water stagnant, thus allowing algae to grow thicker and faster. Further, algal blooms absorb more sunlight, making water even warmer and promoting more blooms.

In different ways

Not all algal blooms are harmful, but some are deadly. They affect the marine ecosystem in different ways. First, the physical presence of so many algae may suffocate fish by clogging or irritating the gills. Second, phytoplanktons use up all the nutrients, grow, die and sink to the bottom, where they are decomposed by bacteria. The bacteria respire using the dissolved oxygen in the water, leading to the depletion of oxygen available for other marine organisms, which eventually suffocate and die. Third, some algal species produce deadly toxins which either kill the animals or accumulate in the body of animals and spread through the food web.

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Yes, the herring fish farts to communicate with and locate each other at night underwater. When it passes gas, the bubbles that emanate give rise to a high-pitched sound that only others of the species can hear. Besides, the fish are noisy only at night. They use the noise to form a close school to stay safe from predators.

Finally, three observations persuaded the researchers that the FRT is most likely produced for communication. Firstly, when more herring are in a tank, the researchers record more FRTs per fish.

Secondly, the herring are only noisy after dark, indicating that the sounds might allow the fish to locate one another when they cannot be seen. Thirdly, the biologists know that herrings can hear sounds of this frequency, while most fish cannot. This would allow them to communicate by FRT without alerting predators to their presence.

Wilson emphasises that at present this idea is just a theory. But the discovery is still useful, he says. Herring might be tracked by their FRTs, in the same way that whales and dolphins are monitored by their high-pitched squeals. Fishermen might even exploit this to locate shoals.

There may even be a conservation issue. Some experts believe human-generated sounds can damage underwater mammals. Now it seems underwater noise might disrupt fish too.

 

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It’s true – sharks have no bones, per se. However, that does not mean that they’re as floppy as a jellyfish. They still have sturdy skeletons and are classified as vertebrates.

So what do sharks have instead of bones? In place of the hard bones that other vertebrates have, sharks have cartilage.

Cartilage is softer tissue, more flexible than bone, but still strong enough to hold muscle and skin in place. It’s the same stuff that you find in your ears and nose.

Can you feel it? You can bend and twist your ears much more than you could, say, your arm.

It’s also what makes babies’ bodies so supple. Humans start with cartilage on which our bones eventually ossify as they grow. That flexibility is how sharks manage to move swiftly through the water, and how they can twist and shake their prey once caught.

 

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There are over 400 species of sharks. Many of them have teeth in layered rows, numbering between five and 15 in their upper and lower jaws. Did you know the bull shark can have 50 rows of teeth? If a tooth falls off, another one grows in its place in a matter of days. Like this, sharks can lose and grow over 20,000 teeth in their lifetime.

Our complete set of 20 temporary teeth is usually in place by age 2 or 3. By around age 18, we have our complete adult set, totaling 32 teeth.

Most sharks have 5 rows of teeth, and can have as many as 3000 teeth at once! It’s a good thing sharks never run out of teeth, as they lose up to 100 per day.

While we use our teeth to bite, chew and grind food, sharks use their teeth to grab, hold and rip prey. Once a shark has grabbed its prey, the shark swallows its food whole. It may not sound polite, but for sharks, it gets the job done.

It’s no wonder sharks don’t get cavities - the surface of their teeth contains 100% fluoride ! The teeth of humans and other mammals contain hydroxyapatite, which is an inorganic constituent also found in bone. It’s important to note, however, that sharks don’t eat sugar.

 

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