In general, the ocean is a life-barren zone, but there are some deep-sea environments with unique properties. These unique environments are like oases in the ocean. Although many are only the size of a football field, the number of life living in these "ocean oases" is hundreds of times that of the ordinary deep sea around them. Often, there are some similarities between these sea areas where life thrives. For example, there are often special geological structures on the seafloor of these oasis sea areas that change the normal deep sea currents. Twisted deep-ocean currents often form concentrated sedimentation areas or upwelling areas on a certain seafloor. The action of deep ocean currents profoundly affects the population structure of the region. Areas with concentrated sedimentation are paradises for deep-sea burrowing creatures, and upwellings bring a large amount of nutrients from the seafloor, providing abundant food for shallow-water inhabitants. Typically, these "undersea oases" appear near special seafloor structures such as hydrothermal vents, undersea mountains or deep-water coral reefs.
The most striking symbol of the submarine hot spring system is a chimney-like hot water vent - the smoke column (a), from which hot water rich in hydrogen sulfide continuously spews out (b). There are a variety of creatures living near the hot spring vents, including tube worms (c), giant clams (d), giant clams (e), deep-sea crabs (f), and short-tailed crabs with degraded vision (g)
Some geothermal vents will be formed around some seabeds with geological activity (such as submarine volcanic areas and ocean spreading areas). In 1977, scientists discovered the first geothermal vent near the Galapagos Islands. Subsequently, hundreds of similar structures were located. In mid-ocean ridges and other geologically active areas, hot magma gradually surges toward the surface of the ocean floor. On the seabed in these areas, seawater seeps into cracks in the Earth's crust until it is eventually blocked by the rock at the bottom of the cracks. These rocks are in close contact with the magma beneath them and are very hot. During the process of seawater seepage, high concentrations of hydrogen sulfide and some other minerals in the cracks will enter the water in large quantities. Eventually the mineral-rich seawater will be heated to about 380°C by the hot rocks at the bottom of the crack. The high temperature causes the water to expand rapidly and erupt again from the cracks. This process forms deep sea hydrothermal vents. Although the normal boiling point of water is 100°C, the water spouted from deep sea hydrothermal springs does not boil due to the strong water pressure of the deep sea. This is because the boiling point of liquid will increase with the increase of pressure. The strong water pressure on the seabed greatly increases the boiling point of water, so that it can still remain liquid at a high temperature of 380°C.
Superheated seawater emerging from the vents cools dramatically when it comes into contact with the cold water of the ocean. Therefore, minerals dissolved in superheated water will precipitate in large quantities, forming a chimney-like sediment layer around the vent, called a plume. The "chimneys" around the vents deposit very quickly, and typically the height of these plumes can grow by about 30 centimeters per day. Eventually, the plume collapses under its own gravity due to being deposited too high, and a new round of deposition begins around the vent. The general height of the "chimney" structure is 10 to 20 meters, but one of the submarine smoke plumes called "Godzilla" is actually as high as a 15-story building and about 50 meters; the diameter of its spout is an astonishing 12 meters. Geothermal vents have a short lifespan, but when one vent dies, new vents often form.
Schematic diagram of submarine black smokestacks
Hydrogen sulfide is often dissolved in the seawater of submarine hot springs. Hydrogen sulfide is a highly toxic chemical with a rotten egg smell that is as toxic to most living organisms as cyanide. In addition to hydrogen sulfide, heavy metal ions such as iron, zinc, and copper also exist in hot spring seawater. If the content reaches a certain level, these metal ions are also toxic. Despite the presence of these toxic chemicals in the environment, the hot spring system is still thriving. In fact, it is toxic hydrogen sulfide that provides life around the vent with the energy it needs to survive. Some bacteria on the seafloor obtain energy from the chemical reaction of hydrogen sulfide, and these bacteria are the beginning of the food chain in hydrothermal vent systems.
Hydrocarbon deposition areas are easily formed in seafloor environments similar to geothermal vents.
For example, on the continental slope, small amounts of petroleum, methane, and hydrogen sulfide may precipitate into seafloor sediments. In areas with large water depths, due to very low temperatures, methane will begin to freeze and form hydrated methane solid, which is also called flammable ice in some literature. In these hydrothermal-like ecosystems, hydrocarbons and hydrogen sulfide deposited on the seafloor provide ample food for chemolithophilic bacteria.
In addition to hot spring systems, submarine mountains are also a rich submarine environment. Seamounts are a type of submarine volcanoes that often appear on plate edges with frequent geographical activity. In addition, magma pockets existing within plates can also form seamounts. Seamounts are similar in shape and structure to volcanoes on land. They all have the characteristics of exposed bedrock, valleys, and volcanic sedimentation accumulation layers. Most seamounts are active volcanoes that can still spew lava, and there are also some dormant volcanoes. In the waters near the Gulf of Alaska, there is an undersea mountain range, the tallest of which is a dormant volcano as high as 3,000 meters.
Undersea Mountain
The first undersea mountain discovered was Mount Davidson, which is located 193.1 kilometers southwest of Monterey City, California, USA. Formed 12 million years ago, the now-silent Mount Davidson is made of mottled volcanic rock, its top covered with a layer of volcanic ash that has been deposited over many years. Mount Davidson is the largest seamount aquatic system in U.S. waters, and the surrounding waters host an abundance of marine life, including considerable numbers of sperm whales and albatrosses.
Generally speaking, coral reefs are mostly formed in tropical sea areas with small water depths, but there are also some cold-water coral reefs in some deep seas. Unlike coral reefs in tropical sea areas, deep-sea coral reefs basically do not require light conditions. Deep-sea coral animals and several species of sponges form dense mounds of mud on the seafloor. These mounds can effectively lock sediments in the ocean and provide the surrounding sea with an environment suitable for fish and invertebrates.
In 1998, scientists discovered hundreds of mud mounds on the seabed northwest of the Scottish coastline. This undersea hilly area named "Darwin's Hills" provides a fertile base for deep-sea coral polyps and sponges. The hilly zone has an average water depth of 1,000 meters and covers an area of ??50 square kilometers. Each of the piles is about 5 meters high and 100 meters wide. The shape of the pile is similar to a comma, with a circular main body and a nearly 100-meter-long drop-shaped "tail" extending toward the southwest. Like other deep-sea environments introduced in this section, submarine mud rises are also a unique submarine structure.
Undersea mud piles are also a unique submarine structure
In 1999, scientists from the University of South Florida discovered an underwater island on the west coast of Florida, Prairie Ridge. A type of coral reef. It wasn't until 2004 that scientists confirmed the authenticity of the discovery. The discovery was shocking mainly because it is the only coral reef on Earth that lives in the deep ocean and is still able to photosynthesize.
The ocean is the largest biological habitat on earth, but human exploration and understanding of it are still very limited. Through the study of ocean surface seawater and shallow water areas, we have gained a lot of knowledge about the physical and chemical conditions in the ocean, and also learned about the living habits of many marine life. However, various difficulties encountered in exploring wider and more distant sea areas have hindered human progress, making the ocean area still a blank on the human scientific map.
The floor of the deep ocean begins at a sharp drop off the continental slope. At the bottom of the continental slope, there is often a small upward slope formed by the accumulation of sediments, called the continental rise. The seabed further away from the continental rise is mainly composed of abyssal plains, and abyssal hills or seamounts often appear on the vast abyssal plains. The center of the ocean basin is divided by the mid-ocean ridge, a belt of submarine volcanoes and earthquakes that circles the globe and is responsible for generating new crust.
As with other environments in the ocean, we use the characteristics of salinity, temperature, density, light, pressure, ocean currents, waves, tides and other factors to describe the deep-water environment. Salinity and temperature work together to determine the density of seawater.
They are heterotrophic organisms that digest their food by secreting digestive enzymes to absorb nutrients.
Schematic diagram of the kingdom Protista
Finally, there are the kingdoms Plantae and Animalia, which are composed of multicellular organisms. Organisms in the plant kingdom, such as seaweeds, trees, and dandelions, cannot move, but they can obtain their own food by converting solar energy into simple carbon compounds. Therefore, plants are all autotrophic organisms. Animals such as fish, whales, and humans are all heterotrophic organisms. They cannot synthesize the substances they need, so they must actively search for their own food.