More than 70 percent of the Earth’s surface is covered by water and it is sometimes referred to as “the blue planet.” Most original life forms evolved in the ocean, and to this day, the marine environment maintains a biodiversity not found in any other ecosystem. Humans are highly dependent on the ocean.
The expression “the seven seas” was used in the past by sailors who sailed across all the world’s oceans. These include the North Pacific Ocean, South Pacific Ocean, North Atlantic Ocean, South Atlantic Ocean, Arctic Ocean (Northern Ocean), Southern Ocean (Antarctic Ocean), and the Indian Ocean. The world ocean, also known as the oceans, is defined as the interconnected water area surrounding the Earth’s continents. The world ocean is divided into three oceans: the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean, with the Pacific Ocean being the largest, covering over 30 percent of the Earth’s surface. Sometimes, the Antarctic Ocean is also considered a separate ocean. The three oceans include delimited seas or sub-seas. A sub-sea or semi-enclosed sea is a delimited part of an ocean. For example, the North Sea, the Arctic Ocean, and the Mediterranean Sea are sub-seas of the Atlantic Ocean.
Several of the world’s seas are relatively warm, but the average temperature of the world’s oceans is only around 3.5 degrees Celsius. This is because the large deep-water basins consist of cold polar water.
A large portion of the open sea areas does not belong to any individual country and is often referred to as the “high seas” or deep sea. These areas constitute almost half of the Earth’s surface, two-thirds of the world’s ocean area, and 95 percent of the world’s ocean volume. The deep sea is not subject to national laws and, in practice, belongs to everyone. The United Nations has long negotiated how these areas should be managed. After more than ten years of intense negotiations, the UN adopted a new binding treaty for the sustainable use of biodiversity in areas beyond national jurisdiction in 2023. This is a step towards fulfilling the global commitments of the international biodiversity agreement from 2022, where the goal is to protect at least 30 percent of the ocean by 2030.
Despite the ocean being a place where various organisms thrive, there are many extreme environments in the sea. From temperatures below freezing to near boiling points in hot underwater springs. Where the sea meets the land, the waves are powerful, UV radiation is high, and it is home to a large biodiversity. Some organisms utilize a wide range of habitats, while others specialize in a single type of environment.
The deep sea is a hostile environment for us humans. At a depth of 30 meters, most light is gone, at 70 to 80 meters, most of the oxygen disappears, and the pressure at the bottom is high. Therefore, very little of the deep sea has been explored. In fact, barely five percent of the ocean’s depths have been explored by humans. Researchers also know less than they would like about the organisms that can live in the deep sea. Moreover, they cannot be brought up and studied in aquariums or laboratories because they are adapted to withstand the high pressure in the depths of the sea.
To live in the depths of the oceans, where light does not reach, animals must adapt to life in darkness. Many have large mouths, light organs, or large and extra light-sensitive eyes. There is also a diversity of microorganisms living in this challenging environment. The fact that life can exist under such extreme conditions without oxygen or sunlight has led researchers to consider that there might be life on other planets that we have previously thought to be lifeless.
Although we still know very little about the organisms of the deep, it is known that overfishing and bottom trawling can also affect deep-sea animals. Many organisms are still undiscovered and therefore at risk of disappearing if fishing continues as it has done so far.
The Mariana Trench in the Pacific Ocean is the world’s deepest place in the sea. The maximum depth is Challenger Deep, which is approximately eleven kilometers below the sea surface. At the same time, the average depth of the world’s oceans is about 3700 meters. Sweden’s deepest point is 560 meters in Bratten in Skagerrak, and the Baltic Sea’s deepest point, Landsort Deep at 459 meters, is west of Gotland.
Ecosystem services
The world’s oceans and seas are a significant asset for us humans. The oceans provide us with a multitude of services. To remind us of the importance of the oceans and the need to protect them, June 8th has been designated as World Oceans Day by the United Nations. But there are more reminders of how important the ocean is in our daily lives.
World oceans give us more than just food. They produce more than half of all the oxygen in the atmosphere through photosynthesis, absorb greenhouse gases, and contribute to tourism. Some well-visited tourist destinations at sea include Gotland, the Koster Islands, and other archipelago areas.
Additionally, hundreds of millions of people depend on fish and other resources from the sea. More than 38 million people are employed in the fishing industry worldwide. The oceans are also widely used as transportation routes.
Coastal ecosystems such as coral reefs, seagrass beds, and mangrove forests are crucial places for the young. They are also significant for people living on the coast as they act as a protection zone against floods, storms, and can serve as wave breakers and erosion protection.
TEXT: Lina Mattsson
Japan's controversial plan to flush out millions of tonnes of stored water from the Fukushima nuclear disaster looks set to be delayed. The construction of the tunnel the water is to rush through is taking time - and the authorities also need to get the public on board.
Sharks equipped with cameras are helping scientists map unknown seagrass beds in the Bahamas.
The crystal clear warm water a few meters below the surface in the complex cave system in Mexico is both mystic and fascinating. Diving in the labyrinths of this natural cave system has given me many lifelong dive memories. Follow me and experience the silent, mystical water world underground.
Rapid climate change vs evolution. The Galapagos cormorant has evolved to thrive in an environment where they can feed near the coast outside the islands where they live. Their wings have shrunk to a third of the size needed for flight and they have become very efficient swimmers. Rapid climate change threatens to disrupt the cold currents that bring nutrient-rich water so close to their remote island home. It is now possible that the millions of years of evolution that have made them so successful in this particular environment will put them at a life-threatening disadvantage
Alaska suspends all snow crab and king crab fishing this year. The authorities' decision comes after a sharp decline in crabs in the Barents Sea and Bristol Bay respectively. It is the first time ever that snow crab fishing has been suspended; for the king crabs, it is the second autumn in a row that they have been protected
Billions of snow crabs have disappeared from the Bering Sea in recent years. Now fishing for the delicacy crabs in Alaska is canceled for the first time
The emergence of the first jaws with teeth was one of the most important events in the history of life on Earth. Now scientists in China have found fossils of jawed fish with the astonishing age of almost 440 million years. They are our oldest known ancestors with teeth
Researchers in Argentina are concerned that several whales have been found dead in the south of the country. They believe a microalgae may be behind the deaths. Between 24 September and 2 October, at least 13 southern capemen have died in a water area near the Valdés Peninsula, an area that is a haven and breeding ground for the
For the third year in a row, groups of killer whales have rammed sailing boats and chewed up their rudders along the coasts of Portugal and Spain. Mikkel Erichsen had his special rendez vous with the killer whales August 9th 2022. Sailing with his wife and three children, they had set out from Norway a few months earlier, ultimately destined for the Caribbean, and perhaps even longer
After a week filming on board the research ship Argo in the Galapagos Islands I finally had my first opportunity to go ashore. I accompanied marine biologist, Doctor Susana Cardenas and Park ranger Alberto Proaño on a trip to Fernandina Island. They were there to tag and to take samples from 2 endemic bird species, the Galapagos flightless cormorant and the Galapagos penguin
It has been known for some time that humpback whales can communicate over great distances. The song is carried along during the humpback whale's long migrations across the oceans and researchers have now seen how local songs have migrated further across the Pacific - from the coast of Australia all the way to Ecuador, reports Vetenskapsradion.
During the summer, there have been alarming reports from the Baltic Sea that the herring is running out. The cod is long gone. The party is over. Of all the world's fish stocks, 90% are fully exploited or threatened with collapse. The oceans are running dry, but there is a sea where there is enough fish for everyone, humans and fish, whales and birds. In northern Norway, the water is teeming with life.
Legendary oceanographer, Sylvia Earle first visited the Galapagos Islands in 1966 and described it as, "the sharkiest fishiest place I've ever been." In July 2022 we return to this special place on a research boat chartered by Dr. Earle's Mission Blue foundation. The expedition is tasked with checking key environmental health indicators on the 25th anniversary of the Galapagos being declared a marine protected area
After an eventful first week in the Galapagos (link to the first article), we are now heading west. We will investigate the waters around Fernandina island in the western part of the archipelago. Here the water is significantly colder and the fauna is different. The cold, nutrient-rich ocean current comes all the way from the South Pole. It creates a completely unique underwater environment. Corals and sharks but unusually, also penguins and kelp
The challenges of wrestling fifteen flight cases loaded with film equipment and dive gear from Stockholm to the Galapagos islands are forgotten the instant we emerge from the airport into the sunshine of Baltra island
Many Norwegian children probably cried themselves to sleep on Sunday 14 August 2022. In the early hours of the same morning, the popular walrus Freya was killed on behalf of the Norwegian authorities
For me, the sea has meant beautiful beaches back home in Brazil or a cold swim in Stockholm. Not much more. But my work for Deep Sea has given me a new perspective on the oceans
The manatee is a large marine mammal that lives in springs, rivers and shallow coastal inlets, including around Florida. Humans are the only serious threat to them and recent years have been difficult, with many animals killed in boat collisions and due to debris. Now, in addition, eutrophication in the sea is threatening their food, seaweed, so as an emergency measure they have started feeding manatees in the most vulnerable place.
Sharks and rays have long been considered "silent" fish - that is, unable to produce sound. Researchers from Sweden and Australia have now shown that this is a misconception, writes SLU (Swedish University of Agricultural Sciences) in a press release.
After five hectic days, the expedition has returned to the main island of Santa Cruz to exchange some scientists and crew. At the same time, the expedition is visited by journalists from CNN and Ecuador's Minister of the Environment, who will accompany them down in the expedition's submarine
An overwhelming majority of the world's glaciers are shrinking and many of them could disappear in the not-too-distant future, according to a series of new studies. This means that we may soon experience the same state as during the postglacial warm period 8,000-4,000 years ago
Most people associate walruses with the Arctic Ocean and eternal ice. So when the young walrus Freya was seen in a port on Smögen in March, many people opened their eyes. Two huge males have also been put near Stavanger and in Hammerfest on the northern tip of Norway. How unique is this?
The Faroe Islands will limit the number of dolphins that can be slaughtered, after the traditional hunting has been heavily criticised. Now no more than 500 white-sided dolphins may be killed per year
The Migration of mega shoals of sardine up the east coast of South Africa has been called the greatest shoal on earth. The wild coast on the east coast of
