How does zooplankton affect marine life?

There's this fast-swimming zooplankton (a small organism) that lives in groups. And it is tiny, growing to about 6 cm. But lying at the base of the food web in the Southern Ocean, the krill is what links the ecosystem together. Its population is on the decline, and this can have an unimaginable impact on marine life in the long run. How?

A new study published recently says krill population in its Antarctic habitat is likely to decline about 30% this century due to both natural climate variability and human activity-induced climate change. The study also adds that it will be difficult to "tell the difference between natural and human-caused effects on krill until late in the 21st century". This is worrisome due to two reasons. One is that unless we know how exactly human activity affects krill population, it may be difficult to initiate relevant steps to improve the situation. Two, it is said that "natural climate variability can obscure human-driven trends". Neither augurs well for the krill population.

As mentioned, krill are tiny creatures. But they are one of the most abundant too. For several sea creatures including penguins, seals, fish, and whales - in the ocean surrounding Antarctica, krill are the main food. Not just that. Many sea animals feed on the creatures that consume krill, which is why the krill has an important role to play in the aquatic food chain, especially in the Southern Ocean. If the krill population keeps coming down, it could affect several other creatures, causing a severe imbalance in the food chain. Krill are adapted to surviving harsh winters. But one wonders how well they can adapt to climate change.

Did you know?

The largest animal on Earth, the blue whale feeds almost exclusively on krill. Apparently, it needs to eat a few tonnes of these tiny crustaceans every day!

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What happens when trees die?

Previously in this column, we learnt about how forests act as carbon sinks. We know that trees absorb carbon from the atmosphere through photosynthesis. The gas then becomes deposited in tree biomass and in soil. But what happens when trees die? Do they release the stored carbon? Yes, they do. But how much? This is something scientists have not measured until recently. A series of new experiments, published in the journal Nature this month, is the first to put a number to this carbon emission. The study carried out by researchers from the Australian National University also draws our attention to the potential role of climate change and insect population in influencing this carbon cycle.

When trees die

When a tree dies, a new life springs forward. Fungi communities flourish on dead wood and small organisms such as salamander and insects create breeding grounds. Logs (dead trees on the ground) and snags (standing dead trees) provide a place to nest, rest, eat and grow for a number of organisms. The trees eventually decompose over a period of time. The speed at which deadwood breaks down depends mainly on interactions between the local climate and the activity of decomposers, such as fungi, microorganisms, and insects. When this decomposition happens, the trees release carbon dioxide, among other gases. The movement of carbon and other gases within forests and soils, thus, occurs in cycles. However, the full picture of the role decomposing wood plays in the global carbon cycle had been difficult to estimate.

Measuring the emission

To estimate how much carbon decaying and dead trees emit and to determine the influence of climate on the rate of decomposition, scientists from the Australian National University studied wood from more than 140 tree species in 55 forest areas on six continents. They conclude that deadwood, which includes fallen trees, standing dead trees, trunks and fallen branches, contain roughly 8% of all the carbon on Earth. Each year, on average, about 10.9 gigatons of carbon are released from decaying woody matter around the world. That's equivalent to 115% of global annual fossil fuel emissions. Of course, not all the carbon released from deadwood goes into the atmosphere. Some becomes trapped in the soil or in creatures that use the wood for food or shelter.

Role of climate change & insects

During the study, the researchers found out that in regions where the temperature and humidity is high, the deadwood weathered and decomposed much faster. They also noticed the role played by the abundance of decomposing insects in these regions. In cooler temperate climes, the opposite happened. The boreal and temperate forests account for less than 7% of carbon released from deadwood each year.

This suggests that climate change might increase wood decomposition in tropical or subtropical areas as temperatures rise.

In recent years, scientists have begun to notice an 'insect apocalypse' occurring around the world, including in the tropics where most insect diversity resides. This dramatic loss of decomposers will have a massive impact on deadwood and its carbon emission. Thus both climate change and the loss of insects have the potential to alter the decomposition of wood, and therefore, carbon and nutrient cycles worldwide.

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What are the fun facts of tardigrade?

Tardigrade is a microscopic animal found everywhere on Earth – from the deep sea in the mud volcanoes. There are around 1300 species of tardigrades. We are also called water bears or moss piglets.

It has eight limbs with four to eight claws on each. Its body is covered in a tough cuticle, similar to the exoskeletons. It is known for being the most resilient animal, because it can survive extreme conditions such as exposure to extreme temperatures, extreme pressures, radiation and starvation. It can go up to 30 years without food and water.

In extreme dry conditions, it gets into a death-like state called cryptobiosis. It squeezes all the water out of its body, retract its heads and limbs and curl up into a little ball. When conditions improve, it unfurls itself and goes about its business. It sucks the juices from algae, lichens and moss using its tube-shaped mouth.

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What are the fun facts of hedgehog?

Hedgehog is a spiny mammal that belongs to the family Erinaceidae, found in Europe, Asia and Africa. It has an elongated snout and body covered with 5000 to 6500 non-poisonous quills. It replaces the old quills with new ones each yea.

If attached it curls into a prickly and unapestising ball that deters most predators. It feeds on insects, worms, centipedes, snails, mice, frogs and snakes. It hibernates in cold climates.

The body of adult hedgehogs ranges from 14 to 30 centimetres long, and their tail can add one to six centimetres. When they are born (there can be up to seven in a litter) their spines are soft and short. But soon after birth, their spines harden, becoming stiffer, sharper and longer. Babies stay in the nest until they”re about three weeks old. By that time, their eyes are open, their spines are effective and they can safely follow their mother outside the nest as she looks for food.

Top on the hedgehog”s menu are insects, followed by small mice, snails, lizards, frogs, eggs and even snakes. Mostly nocturnal creatures, they head out at night in search of food – but they are sometimes active during the day, too, particularly after it rains.

Credit : National Geographic

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Do turtles talk?

Yes, they do, says research. Since turtles don't have vocal cords, it was thought that they did not communicate through sounds. However, scientists have found that turtles communicate at such low frequency that sounds like "clicks, clucks and hoots" can be heard only through a hydrophone. What's surprising is that they talk when they are still inside their eggs just before hatching.

One of the most common sounds which a turtle may produce is the hissing sound. Turtles hiss by quickly expelling air from their lungs. They do this by tucking their heads into their shells.

A turtle in a new environment will hiss a lot as it is not used to its environment. Once the turtle gets used to its environment, you can expect it to hiss less. Snappers) hiss when approached.

They do this because they are stressed and feel threatened. Hissing coupled with heavy breathing produces a menacing sound. A threatened snapping turtle will attack when approached or provoked. Their bites are very powerful and are capable of crushing human bones.

When a turtle hisses, it’s best to leave it alone.

Credit : All Turtles

Picture Credit : Google