The deep sea continues to reveal new secrets, reminding us of its wonder and its vulnerability to emerging threats such as seabed mining.
Take the recent revelations about “dark oxygen.” The conventional thinking until recently has been that oxygen can be made only in the presence of sunlight. That is, plants convert sunlight and water during photosynthesis into the oxygen that marine life and people breathe. However, scientists recently discovered a mind-blowing phenomenon: The deep sea makes oxygen in the absence of sunlight.
Researchers couldn’t believe their findings, so much so that they initially wrote them off, pointing to flawed instrumentation. However, sure enough, the data showed a consistent increase in “dark oxygen” measured at the bottom of the ocean in fields of polymetallic nodules. These are the same potato-size masses coveted by the mining industry for critical minerals used in everything from cell phones to electric car batteries. The nodules, which form over millions of years, are the result of metals such as iron and manganese precipitating out of the water and accreting on a hard object, like a fish bone.
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The research team ruled out other processes that might explain the uptick in oxygen, including microbes.
The researchers hypothesize the dark oxygen is likely the result of electrolysis, the process by which electrical currents split water into hydrogen and oxygen. So, where is the electricity needed to perform this chemical reaction? It is the voltage detected in the nodules themselves. The nodules could act as natural batteries when clustered together in numbers that generate enough juice to split the water molecule into the elements of hydrogen and oxygen.
This is a significant finding because it raises important questions about the role of dark oxygen in the deep ocean where oxygen is naturally scarce. Most marine species, just like people, need oxygen to survive, absorbing oxygen through gills and other apparatuses. Dark oxygen could make all the difference to species in an environment where oxygen is not only naturally limiting but expected to decrease because of climate change. As oceans warm, they lose their ability to absorb and hold oxygen, as the water warms up and stratifies at the surface.
Deep-sea mining could further upend the deep-sea ecosystem by removing the nodules, preventing the production of oxygen that could be key to the survival of animals living there. In addition, we already know that mining will likely create plumes of sediment that would eventually resettle, potentially smothering nodules and interfering with their ability to produce oxygen.
But these and other impacts of deep-sea mining would not be limited to the seafloor. In another recent study, scientists demonstrated that the unwanted tailings from seabed mining activities could expose organisms that live in the water column to harmful contaminants. In a laboratory experiment, they studied the types and amounts of trace metals in the mining wastewater, finding that the levels of cobalt and copper would be 15 times higher than background levels.
Copper is among the most toxic substances known to aquatic organisms. Research suggests that as ocean temperatures and acidification levels increase, this will magnify the toxicity of copper to marine life. What’s more, copper accumulates in fish and other marine species, including species of seafood we eat, posing a potential threat to people who eat fish with elevated copper levels.
Researchers say these copper-laced plumes could be especially problematic for mesopelagic communities (organisms inhabiting intermediate ocean depths) at depths between 200 and 1,000 meters. Why is this significant? Mesopelagic species are critical to ocean carbon sequestration and climate regulation; trillions of hungry animals migrate to the surface each night to feed, and in the process of returning to the deep ocean during daytime they transfer between 2-6 gigatons of carbon annually into the deep ocean.
Mesopelagic species also provide an important food source for marine mammals, seabirds and fishes, including seafood species that support important commercial fisheries worldwide. According to Food and Agriculture Organization dataanalyzed by Ocean Conservancy, an estimated 24 billion pounds of commercially significant fishery species such as tunas, salmon swordfish and squids that eat mesopelagic prey were landed in 2022. Deep-sea mining could potentially pull the rug out from under this incredibly important ecosystem.
Seabed mining could expose these mesopelagic species to toxic tailings, potentially jeopardizing key functions ranging from climate regulation and sustaining ocean food webs to supporting pelagic (open sea) fisheries and putting protein on the table for millions of people.
The more we learn about the deep sea, its unique adaptations and the many services it provides to the ocean and humanity alike, the more the threat of seabed mining comes into clearer focus. Ocean Conservancy supports a moratorium on deep-sea mining and is working with the ocean conservation community and the government to stop this practice before it starts. Recently, Ocean Conservancy signed a letter to President Biden calling for a moratorium, or precautionary pause, on deep seabed mining, domestically and internationally. Additionally we have worked with Members of Congress to oppose deep sea mining. You can take action with us to stop seabed mining.
We can and must grow clean energy to meet climate goals, but this cannot be at the cost of our oceans and local communities. By investing in new battery technology, alternatives to deep sea minerals and circularity in mineral supply chains here at home, the United States can scale its renewable energy sector while reducing its dependence on foreign supplies of critical minerals. This is in the best interest of economic and national security and the long-term health of our oceans and planet.
The post Three New Deep-Sea Discoveries appeared first on Ocean Conservancy.
Ocean Acidification
Dr Heidarzadeh’s TV interview with SkyNews on the massive M7.7 Panama earthquake on 9 October 2026
Dr Heidarzadeh’s TV interview with SkyNews on the massive M7.7 Panama earthquake on 9 October 2026. Click here for the full story.
Dr Heidarzadeh’s TV interview with SkyNews on the massive M7.7 Panama earthquake on 9 October 2026
Our ocean is an incredibly vast and mysterious place. And there is no place where that is more evident than the deepest ocean area in the world: the legendary Mariana Trench. Located east of the Philippines, the Mariana Trench lies in the Mariana Archipelago in the western portion of the North Pacific. The greater area of the Mariana Trench Marine National Monument is made up of more than 95,000 square miles of ocean. Beneath these waters lie incredibly complex aggregations of submerged islands and volcanoes … and of course, an astoundingly massive trench.
Dive in with us to have your biggest questions answered about the famed Mariana Trench.
How deep is the Mariana Trench?
The deepest part of the Mariana Trench, known as Challenger Deep, is almost 36,000 feet below the ocean’s surface. For context, Mount Everest is about 29,000 feet above sea level, so the Mariana Trench is about 7,000 feet deeper than Mount Everest is tall. For one more comparison, the RMS Titanic lies at a depth of about 12,500 feet below sea level. The Challenger Deep is in waters nearly three times deeper than this ship’s final resting place.
Due to its enormous size, the Mariana Trench has at times been affectionately nicknamed the Grand Canyon of the ocean. This is certainly a picturesque image, but don’t let the mammoth size of this U.S. national terrestrial park fool you into thinking the Mariana Trench matches its size. The trench’s footprint is estimated to be 120 times larger than the Grand Canyon’s, and to reach the bottom of Challenger Deep, you’d need to descend through almost six Grand Canyons stacked on top of each other before you’d reach the seafloor.
Oh … and did we mention it’s five times wider than it is deep? It’s about 43 miles wide!
What is Challenger Deep, and how long would it take to reach it?
Challenger Deep is the deepest point of the Mariana Trench. Fewer than 30 people have ever journeyed to this area. The trek below the surface is long, dark and time-consuming, and it’s not an expedition considered lightly by scientists and explorers.
The first people to descend into the depths of this area in 1960 were oceanographers Jacques Piccard and Don Walsh, and it took them close to five hours to reach Challenger Deep. Since then, more advanced submersibles have been created, but it still takes two to four hours for modern vessels to reach such depths. For example, explorer and filmmaker James Cameron reached the seafloor in a little more than 2.5 hours in the first documented solo submarine dive to the area, and it took oceanographer Dr. Dawn Wright about four hours in 2022. It is crucial that these submersibles descend slowly and steadily beneath the surface, as the immense water pressure compounds with every mile a submersible descends. Speaking of pressure …
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What is the water pressure at the bottom of the Mariana Trench?
If you thought the depth of the Mariana Trench was its only jaw-dropping feature, think again. Water pressure is one of the most important factors affecting deep-sea life. In the ocean, pressure increases by one atmosphere for every 33 feet (10 meters) of depth. One atmosphere (a unit of measurement for pressure equivalent to average air pressure at sea level) is equal to about 14.7 pounds per square inch (PSI), which is the approximate standard atmospheric pressure at sea level. If you were to convert atmospheric pressure into weight, one atmosphere is about the weight of a bowling ball. Stay with me, friends.
If a vessel were to dive 2,000 feet below the surface, the pressure would equal that of 60 bowling balls stacked atop every square inch of that submersible. But 60 bowling balls is simply nothing compared to the pressure in the Mariana Trench. The atmospheric pressure at the depths of Challenger Deep is equal to about 16,000 PSI. That pressure is about the same as the weight of an entire full-grown elephant on every square inch of a submersible!
Need a more extreme comparison? If a human were to be placed at the bottom of the Mariana Trench, the pressure would be equal to that of 50 jumbo jets piled on top of a person!
Do any animals live in the Mariana Trench?
The depths of the Mariana Trench come with immense pressure and extreme darkness, but somehow, life finds a way to survive. Organisms that live at an extreme depth, like that of Challenger Deep, have to be highly adapted to low temperatures (typically just above freezing), high pressure and virtually no light at all.
Species found in the depths of the Mariana Trench might look vastly different from animals from other ocean depths because their anatomy has been refined to thrive in harsh conditions. At such great depths, these animals typically depend on chemosynthesis (using nutrient-rich waters being pumped out of hydrothermal vents) or descending detritus (dead matter that has fallen from higher parts of the ocean) for food, such as whale falls. Just a handful of these animals include species of octopuses and squids, sea cucumbers, amphipods, sea jellies, shrimp, sea worms and some wild-looking fish!
In 2025, more than 7,000 new species were discovered in the Mariana Trench, including the hadal snailfish (Pseudoliparis swirei). This is the deepest-dwelling fish currently known to science. Now, the fish has been dubbed “the Mariana snailfish.”
How was the Mariana Trench formed?
The process by which the Mariana Trench was created is a geologically fascinating one known as subduction. On the Earth’s surface, there are thin plates that cover the planet’s mantle, which is made of molten rock. If two of these plates collide, one pushes down into the Earth’s mantle while the other is pushed over the bottom plate. When this happens, a trench is formed from the drag of the bottom plate. This process can sometimes create incredibly strong earthquakes. The plates that forged the Mariana Trench’s creation are estimated to be up to approximately 180 million years old.
This trench was unknown to scientists until 1875. It was then that a team of explorers on the HMS Challenger measured the depth of the sea by simply lowering a weighted rope into the water. They were baffled when they measured that first portion of the seafloor to be five miles below the surface. And so was born the origin of some of the most daring deep-sea explorations known to mankind to date.
Is the Mariana Trench protected?
The Mariana Trench is in waters off Guam and the Mariana Islands. The region is protected from some human activities under its status as a marine monument. The creation of the Mariana Trench Marine National Monument signified that international, national and local leaders all recognize the importance of protecting this area.
However, just because the region is protected does not mean it’s not vulnerable to modern threats to ocean health. Plastic bags have been spotted in the Mariana Trench during several expeditions, highlighting the far-reaching impact of the marine debris problem. No corner of our ocean is safe from the ever-present threat of plastic pollution. The reality of a changing climate makes the future well-being of wondrous places like the Mariana Trench uncertain. What’s more: More than 70% of the global ocean has yet to be mapped. And what we don’t yet know about, we cannot wisely work to protect.
It’s up to us to work together to defend our ocean, from the sandy shores of our favorite beaches to the deepest, darkest parts of the sea. Together, we can work to protect our ocean as a whole, which ultimately helps protect treasured places like Challenger Deep.
Find out how you can join Ocean Conservancy’s wave of momentum to secure a healthy ocean and a thriving planet, forever and for everyone!
The post The Mysteries of the Mariana Trench appeared first on Ocean Conservancy.