coral
On the surface, it is a plant, but it is actually an animal, and it is related to the anemone.
They filter and feed on plankton in the water and secrete calcium carbonate skeletons that accumulate over time to form coral reefs, the most biodiverse ecosystems in the oceans. The world's largest biological structure, the Great Barrier Reef off the east coast of Australia, is the result of the accumulation of corals from generation to generation. In many warm tropical seas, there are brightly colored shallow-water corals (their color is mainly due to the action of symbiotic algae that live inside the cells of polyps), and deeper in the ocean, there are many lesser-known cold-water corals. On the western side of Eurasia, beneath the long coast from Norway to the south to the coast of Africa, hides a 4,500-kilometre stretch of cold-water coral, about 2.5 times the length of Australia's Great Barrier Reef. Under the dark waters, the densely packed corals are breathtaking, and they are also home to many marine fish, and their biodiversity is comparable to that of tropical corals. Scientists have found more than 130 species of marine life on a single cold-water coral plant alone. Because cold-water corals generally grow in the dark and icy deep seas 100 to 1,000 meters below the ocean surface, even scientists have only confirmed their real existence more than a decade ago. Even less is known about their situation.
So, what kind of effect does ocean acidification have on corals? According to the basic knowledge of chemistry, carbon dioxide is dissolved in water, combined with water to form carbonic acid, a part of the carbonic acid is retained in the original form in the water, and a large number of them are separated into acidic hydrogen ions and bicarbonate ions, chemists usually use the familiar pH value to quantify hydrogen ions: pH drops by 1 unit, equivalent to the concentration of hydrogen ions increased to 10 times the original, the acidity of water is stronger; pH rises by one unit, equivalent to the concentration of hydrogen ions decreased to 1/10 of the original, the alkalinity of water is stronger neutral pH ( Pure water has a pH of 7. The pH of the original seawater is 8 to 8.3, which means that in its natural state, the seawater is slightly alkaline.
There are two types of calcium-rich rocks in the ocean:
Aragonite
aragonite and calcite,
calcite
The calcium carbonate in the ocean is derived from the dissolution of these two rocks. The animal plankton (pterodactyls) and corals in the ocean usually use the calcium carbonate of the aragonite to form the support structure of the body, which is very hard, while the body support structure of the plant plankton (cobblestone algae) and foraminifera is composed of calcite calcium carbonate. Because aragonite is more soluble than calcite, pterodactyls and corals may be affected by ocean acidification earlier. Taking corals as an example, when the ocean acidifies, carbonate ions decrease, the material that forms coral bones decreases, and coral growth slows down; when the concentration of calcium carbonate in seawater falls below the saturation point, the formed bones of corals dissolve to compensate for the lack of calcium carbonate.
Originally, it was believed that warming seawater can promote tropical corals to grow faster, thereby counteracting the slow growth caused by acidification, but in-depth research proves that this view is not correct, because corals are very sensitive to temperature changes, even if the sea temperature changes are small - even if it is only above the annual average temperature of 1 ° C, corals will be forced to take "expulsion action" in a considerable period of time - to drive away the symbiotic algae that provide food in the body. These symbiotic algae are brightly colored, and their absence means that corals will turn white in a very short period of time, and reproduction and the manufacture of calcareous bones will be hindered, or even die, which is the so-called "coral bleaching event". The bleaching of tropical corals is now very serious.
In the past, it was thought that coral dissolution caused by ocean acidification would not occur at least this century, but the latest research proves that under the double whammy of warming seawater and reduced carbonate concentrations, corals may become very rare by the middle of this century in just a few decades; if acidification is not curbed, corals may disappear from human vision by the end of the century.
For cold-water corals, because they mostly grow in the deep oceans of the North Pacific and North Atlantic, where calcium carbonate is unsaturated, ocean acidification will bring them a crisis sooner than tropical corals.
In addition to corals, zooplankton are also affected. We know that the shell of zooplankton is mainly composed of calcium carbonate, when calcium carbonate is reduced due to ocean acidification, the growth of zooplankton shell will be affected, and even the shell will appear terrible dissolution when it is severe. This is a very serious problem because zooplankton play a pivotal role in the marine ecological chain, and many marine fish such as cod, salmon and whales feed on them, so a variety of marine fish that feed or inhabit zooplankton and corals are affected by ocean acidification.
Now, what scientists want to know most is the extent to which marine life can adapt to ocean acidification. A new study suggests that some corals have begun to adjust their survival strategies by using calcite instead of aragonite to build their own skeletons. However, the researchers found that this abandonment strategy that corals were forced to adopt was in response to a decline in magnesium concentrations in seawater, not for high concentrations of carbon dioxide. In addition, corals that build bones from calcite grow very slowly.
In 2016, during the spring bloom outbreak, a trial conducted by the famous marine biologist Roy Burson showed that when the concentration of carbon dioxide was set to 1x, 2x, and 3 times the current level, a single-celled seaweed was unable to generate a fine shell within 5 weeks. This single-celled seaweed is the most elementary producer of the ocean, and usually this tiny organism requires very little energy to form a shell. It can be seen that the impact of ocean acidification on marine life cannot be underestimated. So, in the face of this situation, what countermeasures does mankind have?