ABYSSAL PLAINS

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Picture Courtesy:  https://scitechdaily.com/mysterious-unknown-deep-sea-creatures-discovered-on-abyssal-expedition/

Context: The recent deep-sea expedition to the Abyssal Plains in the Pacific Ocean has unveiled mysterious and fascinating creatures that inhabit these least-explored regions of the Earth.

Details

• The expedition, which lasted for 45 days, focused on the Clarion Clipperton Zone between Mexico and Hawaii. This area is characterized by depths ranging from 3,500 to 5,500 meters and is relatively unexplored, with only a fraction of the animal species described by science.
• Despite being termed "plains," the Abyssal Plains are not entirely flat. They feature ridges, small seamounts, and varying topography. The environment is extremely nutrient-poor, with nutrients primarily originating from hot springs, whale cadavers, and marine snow.
• Animals in these deep-sea areas have adapted to survive in an environment with limited nutrition. Filter feeders, such as sponges, and sediment feeders, such as sea cucumbers, dominate the ecosystem. The lack of food causes individuals to live far apart, but the species richness is surprisingly high.

Some notable discoveries include:

• Transparent-bodied sea cucumbers known as 'unicumbers'
• Pink sea pigs, slow-moving sea cucumbers with remodelled feet used to gather food
• Cup-shaped glass sponges with an exceptionally long lifespan of up to 15,000 years

About Abyssal Plains

• Abyssal plains are situated on the deep ocean floor, found at depths between 3,000 and 6,000 metres. They lie between the foot of a continental rise and a mid-ocean ridge.
• The creation of abyssal plains is a result of plate tectonics and the spreading of the seafloor.
  • Magma rises from the asthenosphere to form new oceanic crust at mid-ocean ridges.
  • As this crust spreads, it blankets the originally uneven surface of the oceanic crust with fine-grained sediments, primarily clay and silt.
• The sediments that blanket abyssal plains are deposited by turbidity currents, which transport material from continental margins into deeper water.
• Abyssal plains often contain metallic nodules with varying concentrations of metals like manganese, iron, nickel, cobalt, and copper. Other elements such as carbon, nitrogen, phosphorus, and silicon are also present.
• Despite their harsh conditions, abyssal plains are believed to be major reservoirs of biodiversity. They play a significant role in ocean carbon cycling, dissolution of calcium carbonate, and atmospheric CO2 concentrations.
• Abyssal plains face challenges such as darkness, extreme water pressure, and oxygen scarcity, making them inhospitable for many organisms. Deep-sea coral reefs are primarily found in depths of 3,000 meters and deeper.

Abyssal plains were not recognized as distinct features until the late 1940s, and systematic studies of these regions have been limited. They are poorly preserved in the sedimentary record due to the subduction process consuming them over time. Abyssal plains are difficult to explore due to darkness and extreme water pressure, which can reach about 750 times atmospheric pressure.

Source:

ScienceDaily

Wikipedia

PRACTICE QUESTION Q. The extreme environment of the Abyssal Plains presents unique challenges for life. Which of the following adaptations are commonly observed in these organisms? 1.  Enhanced eyesight to navigate in the perpetual darkness. 2.  Gigantic size to compete for scarce resources. 3.  Bioluminescence to create their light source. 4.  Specialised feeding mechanisms to filter organic matter from the water column (marine snow). 5.  Highly mobile bodies actively search for food in vast stretches. How many of the above statements are correct? A) Only two B) Only three C) Only four D) All five Answer: A