Category Sea/Ocean

What are the species in the wild that change their appearance to escape predators?

There are many species in the wild that change their appearance to escape predators. This is camouflage. But did you know that some species can even change their gender? Let's read up on them.

CLOWNFISH

Clownfishes live in social groups and consist of a dominant female (the largest in size) surrounded by a male and other immature juveniles. Their social hierarchy is based on size and determines the breeding. In a group, the fishes age and grow larger together, without any change in the hierarchy. But this changes when a dominant female dies. When this happens, others will try to use the opportunity to climb up in rank. The male will rapidly change sex to fill in the vacated position. And another fish will turn into a mature male and complete the breeding pair.

HAWKFISH

The hawkfish which is found on coral reefs from Australia to Japan lives in harems (one male with several females). These reef dwellers basically start life as females. Things change when there is a shift in the number of females in the harem. If a male takes on more females into the harem, then, one of the females changes its sex and becomes a male. It then breaks away from the harem and in the process takes half of the harem along with it. It has also been observed by researchers that when a new male gets challenged by another male, it reverses its sex back to a female. This bi-directional sex change is seen in certain reef fishes.

BLACK SEA BASS

Black sea bass is a commercially important species. These are capable of switching their gender from female to male. They are born as females in the wild. They turn into males when they are two to five years old. Research on sea bass reveals that sex change occurs when there is a dip in the male population. If the female sea bass senses a decrease in the male population, they switch their sex.

BANANA SLUG

Banana slugs are wormlike mollusks and they grow up to 10 inches. These animals are hermaphrodites, that is they have both male and female organs. So they don't change their sex back and forth but are unique as they can use both their male and female reproductive organs at the same time. This they do to self-fertilise when necessary. Even when they are capable of self-fertilisation, the majority of banana slugs will take a partner.

GREEN FROG

Researchers have found that frogs spontaneously change sex in the lab and the same has been seen in the wild. In fact, among the green frog population, this sex change is quite common. Earlier research established that sex reversal in frogs may be related to pollution introduced by humans. When exposed to some pollutants (synthetic estrogens and herbicides) in the lab, it has led to genetically male frogs developing outwardly as females. Further studies have proved that this change could be a natural occurrence in amphibians, even in pollution-free settings.

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How do oceans play an important role in ecology?

Oceans cover more than two-thirds of Earth. Understandably, they play a vital role in keeping all life forms going. World Oceans Day (June 8) just went by, reminding us that an important natural resource is in need of our urgent support.

The importance of ocean

Initially, our ancestors were nomads, moving from one place to another. However, they eventually started settling in one place invariably around waterbodies such as rivers, lakes, oceans, etc. For thousands of years, oceans have been the backbone of human survival. But for even longer, they have been inevitable for all life forms, from the tiniest to the largest. All living beings, even those on land, are directly or indirectly dependent on the ocean for their very existence.

We all breathe easy because all oceans together produce at least 50% of the planet’s oxygen. Due to their sheer size, oceans distribute heat from the Equator to the Poles, regulating the world’s climate. Without this, different regions will constantly experience only extreme weather. Marine life is a good source of food for both humans and animals the world over. In addition, some also have medicinal properties. Oceans are also crucial for global economy since they help in transport and tourism.

What is ailing them?

Oceans face several threats today. Thanks to global warming, our oceans are warming too. This affects marine life since many cannot survive warmer waters. When a few species struggle, they can affect others that are dependent on these species, and this can result in ecosystem collapse. Further, warming waters can increase sea levels, resulting in natural disasters. Human activities such as overfishing, plastics, polluted wastewater discharged into the oceans, etc. affect the natural balance in a marine ecosystem.

According to the U.N., “With 90% of big fish populations depleted, and 50% of coral reefs destroyed, we are taking more from the ocean than can be replenished.” The U.N. calls for us to work together in such a way that we not just take less from the oceans but help these natural resources flourish.

The theme for 2023

The theme this year is “Planet Ocean: tides are changing”. The United Nations will work with people from different walks of life – from policy-makers, indigenous leaders, and scientists to private sector executives, citizens, and youth activists to turn the spotlight on oceans.

What is the 30 X 30 target?

At the 2022 United Nations Climate Change Conference or Conference of the Parties of the UNFCCC, more commonly COP27, held in Egypt last November, as many as 112 nations took an important pledge. They promised to take steps for protecting at least 30% of Earth’s land and ocean by 2030 to help curtail biodiversity loss and climate change.

Did you know?

  • The ocean is key to our economy with an estimated 40 million people being employed by ocean-based industries by 2030.
  • Oceans absorb about 30% of carbon dioxide produced by humans, buffering the impacts of global warming.

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An underwater forest?

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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Why do epaulette sharks walk on land?

Researchers at a Florida university say a species of shark with the ability to walk on land is evolving to survive warming seas and the climate crisis.

The epaulette shark, found on shallow reefs of Australia and New Guinea, can walk for upto 90 feet on dry land using its paddle-shaped fins, and survive hypoxia (deficiency of oxygen) for up to two hours. The 3 foot long sharks are able to slow and fast walk, as well as swim, giving them an exceptional ability to cross land to reach more favourable environments.

Tide pools and coral reef environments are subjected to warm temperatures when the tide is out. These sharks can move from tide pool to tide pool, allowing them to access new pools to forage for food or tide pools with better oxygenated water.

What sets epaulette sharks apart from other shark species with these abilities, is their tolerance of hypoxia for a prolonged period, and ability to not only survive being on land but walk distances up to 30 times its body length. This gives them better agility to evade predators, reach areas with more plentiful food and less competition for it.

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Why was the Arctic Ocean, the smallest of all oceans, in the news recently?

The Arctic Ocean, which is the smallest of the world’s oceans, lies close to the North Pole. Along with its marginal seas the Chukchi, East Siberian, Laptev, Kara, Barents, Greenland, and Beaufort, the Arctic Ocean has the least-known basins and bodies of water in the world’s oceans due to its remoteness, difficult weather, and perennial or seasonal ice cover.

About four million people live in the Arctic region. Many of them are indigenous groups that have thrived in this harsh climate for hundreds of years. They rely mostly on the ocean resources for surviving this harsh climate and generate livelihood through these activities. Fishing, sealing, whaling, and other activities are their livelihood means. The U.S., Canada, Greenland, Iceland, Norway, and Russia all have territories that reach into the Arctic Ocean.

The Arctic Ocean is in the news these days because of its effects on global warming. Rising temperatures in the Arctic are expected to cause large amounts of fresh melt-water to enter the north Atlantic, an event that will possibly disrupt global ocean current patterns. This will lead to drastic changes in the Earth’s climate. When the extent of sea ice diminishes and the sea level rises, the effect of storms (such as the Great Arctic Cyclone of 2012) on open water increases. Reduced sea ice also leads to increased human-animal conflicts. It will, for example, cause polar bears to search for new sources of food, forcing them to move into human territories. Since December 2018, the archipelago of Novaya Zemlya has been under a mass invasion of polar bears, and in February 2019, a state of emergency was declared there. Dozens of polar bears were entering homes, public buildings, and inhabited areas in search of food. All this led to the Arctic Ocean being in the news.

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What has caused the decline in grey whale numbers?

Often, conservation stories underline the importance of the role of all creatures-big and small-for balance in ecosystem. For instance, krill crustaceans barely two inches long are a huge link in the global food chain. If such a small organism can have a telling impact on the food chain, one can only imagine the kind of effect larger animals have in an ecosystem. So, when the population of a large animal plunges, it is always a cause for concern.

Grey whales are among the largest animals on Earth- nearly 50 feet long and weighing over 40 tonnes. These giants are known for their long annual migration of more than 15,000 km “between feeding grounds in the Arctic and breeding grounds in Baja Mexico” Recent research has revealed that the number of these fascinating creatures is witnessing a worrying slump- by nearly 40% in just six years. From 27,000 whales in 2016, the number stands at a concerning 16,650 today. Several factors are attributed to this decrease. One of them is the increase in strandings in 2019, when about 600 of these creatures washed up dead along the west coast of North America Though boat collisions and killer whale attacks caused a few of these deaths most of the dead whales were malnourished which takes us to n crucial of interconnectedness in an ecosystem. It is believed that the malnourishment could be the result of “the whales’ food sources of tiny crustaceans and other invertebrates they prey on in the Arctic shifting due to environmental changes. Further, the overall population among West Coast grey whales “coincides with diminished reproduction” While there were 383 baby whales during the calf production season last year, there have been a mere 217 newborns this year – “the lowest number since such counts began in 1994”

Grey whales were close to extinction several decades ago due to commercial whaling before their population improved due to timely conservation efforts. Even then, the 80s and 90s saw a plunge of about 40%, and eventually they rebounded. It is important for this whale population to recover too because they keep the population of certain other creatures in the food chain in check. Even in death-as carcasses- these large marine mammals help feed several other organisms.

Often, grey whales are washed up dead along the U.S. west coasts. Though boat collisions and killer whale attacks cause some deaths, researchers say malnourishment is a major reason. With tiny crustaceans and other invertebrates shifting due to environmental changes, the grey whales are left without food.

Picture Credit : Google