Here's How Life At The Bottom Of The Ocean Survives Without The Sun

The mysteries of our ocean are not fully understood. The deepest, darkest areas may conjure up ideas of monsters like the megalodon from the Jason Statham movie. Though there are creepy creatures down there, like the methane-powered sea spider, not everything is nightmarish. A recent expedition to the deep hadal zone uncovered a fascinating world that changes our understanding of how life at the bottom of the ocean survives without sunlight — chemical leaks from the ocean floor.

The study was published in the journal Nature on July 30, 2025, and is titled "Flourishing chemosynthetic life at the greatest depths of hadal trenches." This mission brought together scientists from the Chinese Academy of Sciences, the Russian Academy of Sciences, and the Victoria University of Wellington in New Zealand. They undertook the journey personally, not remotely nor by underwater drone, to spearhead this discovery.

At the very bottom of the ocean, more than six miles down, the hadal trench has some of the most extreme and least explored environments on Earth. Its name is inspired by Hades, the Greek god of the underworld. By using a manned deep-sea submersible, the scientists made a remarkable find. They uncovered the deepest and largest chemosynthesis-based communities that have ever been documented.

The scientists explored the Kuril–Kamchatka and Aleutian trenches with the submersible Fendouzhe. The team found that since life in these trenches cannot rely on photosynthesis, it gets its energy from methane and hydrogen sulfide that seeps through cracks in the seafloor. This discovery suggests that these chemical-powered ecosystems may be much more common in the deep ocean than originally thought. It changes how we understand extreme life and carbon cycles on our planet. The communities discovered stretched for 1,553 miles. That's about the driving distance between New York City and Dallas, Texas.

These trenches were formed where tectonic plates collided, the same type of movement that created one massive underwater volcano off the U.S. coast. As a result, the seafloor in this region is extremely geologically active. That constant movement creates cracks through which fluids rich in methane and hydrogen sulfide can escape.

Xiao Xiang, a scientist for the Mariana Trench Environment and Ecology Research project and professor at Shanghai Jiao Tong University (SJTU), told SJTU news, "Our research showed the hadal zone microbes exhibit extraordinary novelty and diversity, demonstrating the immense resource potential of the hadal microorganisms in terms of new genes, new structures and new functions."

This discovery expands what scientists know about where life can survive in the ocean's deepest trenches. Until now, most researchers believed animals at these extreme depths depended on food falling from the surface such as organic debris and carcasses. Instead, this research demonstrates that chemical energy plays a much bigger role than expected. Studying how worms, clams, and microbes adapt to the crushing pressures and chemically rich environments can reshape our understanding of the limits of life on Earth.

A researcher on the team, Zhao Weishu, also told SJTU news, "... we found that living things eat some refractory carbon matters, which are generally difficult to be utilized, in the hadal zone, a region where food source is fairly limited. If such a practice is replicated in the shallow sea area, it may help solve problems, such as oil spills and plastic pollution."

This discovery also impacts how we understand carbon and climate. The unusually high levels of methane found in these trenches suggest they act as carbon reservoirs, locking away organic carbon in the form of methane for long periods of time. This means that deep sea ecosystems may play a much larger role in Earth's carbon cycle than scientists realized. It may even help explain what is happening to Earth right now that current climate models struggle to explain. Incorporating these new discoveries into global carbon models will be crucial to improve predictions about climate change and Earth's long-term carbon balance.