Evolution: life in deep sea (Evolution)

by David Turell , Tuesday, July 25, 2023, 15:47 (277 days ago) @ David Turell

No light, no carbonates, no shells:

https://www.sciencealert.com/a-hidden-line-deep-in-the-ocean-divides-animals-into-two-c...

"Deep under the ocean, not all ecosystems are built alike.

"And, as an international team of scientists has now found, the very deepest depths are dominated by a particular kind of organism. Below a depth of around 4,400 meters (14,436 feet), most of the creatures lurking in the darkness have soft, squishy bodies. It's only above that line that hard-shelled mollusks are generally found.

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"'But as deep exploration and technology progressed, these ecosystems keep unveiling a large biodiversity, comparable to that in shallow water ecosystems, only found on a much wider spatial spread."

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"Using deep-sea robots, Simon-Lledó and his team collected a large database of images from an abyssal plain known as the Clarion-Clipperton Zone, extending 5,000 kilometers (3,107 miles) at the bottom of the Pacific Ocean between Mexico and Kiribati at depths between 3,500 and 6,000 meters.

"They painstakingly cataloged all the animals they could find larger than 10 millimeters in size from these images. They indexed more than 50,000 abyssal creatures – and they noticed a marked difference in the types of animals found in shallower depths compared to those at the very deepest parts of the zone.

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"Hard shells are formed from calcium carbonate, which diffuses through the ocean from the surface. Below a certain depth, however, insufficient calcium carbonate remains, leading to a lack of it on the seafloor, to be taken up by hard-shelled fauna.

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"'Overall, this reflects a much higher ecological heterogeneity, at multiple scales, than was previously expected for benthic assemblages across the northeast Pacific abyssal seabed," the researchers write in their paper.

"'This overlooked heterogeneity, stemming from geochemical and climatic forcing, has crucial implications for future ecological and macroecological research in abyssal communities and for the success of regional-scale conservation strategies implemented to protect biodiversity in the Clarion-Clipperton Zone and probably in other abyssal areas targeted by deep-sea mining worldwide.'"

Comment: it seems life can survive anywhere and adapt to any set of conditions with its ecosystem intact. The many photos are worth a look.