Category Sea/Ocean

What is the record held by the Mariana Trench?

The Mariana Trench is not only the deepest oceanic trench on Earth but also holds the two lowest points on the planet. This crescent- shaped trench is located in the Western Pacific, east of the Mariana Islands near Guam. The region around the trench is known for many unique environments, such as vents bubbling up liquid sulfur and carbon dioxide, active mud volcanoes, and marine life adapted to pressures 1,000 times more than at sea level.

The Challenger Deep, the southern end of the Mariana Trench, is the deepest spot in the ocean. The National Oceanic and Atmospheric Administration, in 2010, used sound pulses sent through the ocean and calculated the Challenger Deep to be 10,994 metres deep even though it was considered almost impossible to measure its depth. In 2021, pressure sensors were used to calculate its depth and it was discovered that the deepest spot in Challenger Deep was 10,935 m. The ocean’s second-deepest place is also in the Mariana Trench. The Sirena Deep, which lies 200 kilometres to the east of Challenger Deep, is 10,809 metres deep.

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What killed off billions of Alaska’s snow crabs?

Alaska’s snow crabs are named so for their love of cold water, which they inhabit. But, due to the heatwaves in 2018 and 2019, their habitats were not cold enough, and this is suspected to be the “key culprit in the mass die-off. The warmer are believed to have affected the species in more ways than one.

Recently, the Alaska Department of Fish and Game announced that the Bering Sea snow crab season will stay closed for catching during 2022-23 to conserve and rebuild the species. (Though they are found in a couple of other places too, it is in Bering Sea that these crabs are abundant and also grow to reach “fishable sizes”.) The announcement follows an annual survey by the National Oceanic and Atmospheric Administration, which discovered that the crustacean numbers “fell to about 1.9 billion in 2022, down from 11.7 billion in 2018”, a reduction of nearly 85%. What caused this dramatic loss, and how will closing the season help the species? Come, let’s find out.

Alaska’s snow crabs are named so for their love of cold water, which they inhabit. But, due to the heatwaves in 2018 and 2019, their habitats were not cold enough, and this is suspected to be the “key culprit’ in the mass die-off. The warmer temperatures are believed to have affected the species in more ways than one. For instance, studies “have pointed toward a higher prevalence of Bitter Crab Disease as the temperature heats up”. Further, unlike in cold waters, these crabs “need more energy to stay alive” in warmer waters, causing them “metabolic stress”, which likely led to limited movement, and eventual starvation. Apart from this, young crabs require low temperatures of water where their mobility is high, helping them evade predation. When the waters warm, they slow down, and their chances of being targeted by their major predator- the Pacific cod – are higher. 5

However, it is interesting to note that a marine biologist has said that the current predicament was linked more to climate change rather than to overfishing because fishing “removes only large adult males” but the decline in population appears across all sizes of snow crabs. If that’s the case, what explains closing the area for catching these crabs?

Because, the temperature of the water has now returned to normal; closing will help the reproduce and recover. Comfortingly, “this years survey saw significant increases in the immature crabs compared to last year”.

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What are the specialities of the giant kelp?

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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What are the specialities of the Great Barrier Reef?

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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Which is the largest animal on Earth?

Blue whales are the biggest animals that have ever inhabited our planet. These marine mammals grow up to 22 metres in length and to a weight of 150,000 kilograms. Their tongues alone weigh as much as an elephant in some cases and their hearts can be as big as an automobile.

The most interesting detail about these huge creatures is the fact that they reach these immense body sizes by consuming tiny shrimp-like animals called krills alone. In some seasons, a single adult blue whale eats about 4000 kilograms of krill a day.

Blue whales belong to the family of baleen whales. Baleen is a fringed plate made of fingernail-like material that is attached to their upper jaws. These giant animals feed by first gulping a great amount of water through their mouth and then they expand the pleated skin on their throat and belly to take it in. After this, the whales use their massive tongue and force the water out through the thin, overlapping baleen plates. This process leaves behind a large volume of krill, which gets consumed by the whales. Blue whales are found in all the oceans, except the Arctic. They occasionally swim in small groups but they move about in pairs or stay alone.

They now face a severe threat due to whaling and are considered endangered according to the IUCN Red List.

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Why are whale sharks different?

Whale sharks are the largest fish to be identified and can grow up to 10 metres in length. They consume a wide variety of sea animals and planktons in a rather interesting manner. They just keep their mouths wide open and scoop the tiny plants and fishes as they move close to the surface of water.

The whale shark belongs to the category of filter feeders, just like the world’s second largest fish, the basking shark. This means that their huge jaws filter everything it comes across, to find its food. This mechanism is similar to that of the baleen whales, where too, a cross-flow filtration is observed. These giants prefer warm waters and are found in all tropical seas. They also migrate to the continental shelf of the central west coast of Australia during the spring season. During this time, the coral spawning of the Ningaloo Reef of this region provides the whale shark with plenty of plankton to feed on.

Although whale sharks are massive, they are very docile. They even allow swimmers to hitch a ride at times! Currently listed as a vulnerable species, these animals face the threat of hunting, as in some parts of Asia, people continue to hunt them.

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