"Red tide", commonly known as "red ghost", is also known as "harmful algal bloom" internationally. Red tide, also known as red tide, is an abnormal phenomenon in marine ecosystem. It is caused by the explosive reproduction of red tide algae in the family Algae under specific environmental conditions. Seaweed is a huge family. Except for some large algae, many of them are very tiny plants, and some are unicellular plants. Due to the different species and quantity of red tide organisms, seawater can show different colors such as red, yellow and green.

After the occurrence of red tide, except that the seawater becomes infrared,

First, a large number of red tide organisms gather in the gills of fish, causing fish to die of hypoxia and suffocation;

Second, after the death of red tide organisms, algae consume a lot of dissolved oxygen in the water during the decomposition process, which leads to the death of marine organisms such as fish due to hypoxia, and also releases a lot of harmful gases and toxins, which seriously pollutes the marine environment and seriously destroys the normal marine ecosystem;

Third, fish eat a lot of toxic algae.

At the same time, the pH value and viscosity of seawater will also increase, and plankton other than red tide algae will die and rot. Red tide algae also died in large numbers due to explosive proliferation and excessive aggregation.

Red tide is produced under specific environmental conditions, and there are many related factors, but marine pollution is one of them. A large amount of wastewater containing various organic substances is discharged into seawater, which promotes the eutrophication of seawater and is an important material basis for the proliferation of red tide algae. A large number of studies at home and abroad show that marine phytoplankton are the main organisms that cause red tides. There are more than 260 species of marine phytoplankton in the world that can form red tides, and more than 70 of them can produce toxins. Some toxins secreted by them can directly lead to a large number of deaths of marine life, and some can even spread through the food chain, causing human food poisoning.

At present, more than 30 countries and regions in the world have been harmed by red tides to varying degrees, and Japan is one of the countries that suffer the most. In recent ten years, due to the increasingly serious marine pollution, the red tide disaster in China has also increased, from a few scattered sea areas to a sea area, and some important breeding bases have been particularly seriously affected. It is a complex system engineering to study and prevent the occurrence and harm of red tide, which involves many disciplines such as biological oceanography, chemical oceanography, physical oceanography and environmental oceanography.

Red tide is a harmful ecological phenomenon that some phytoplankton, protozoa or bacteria in seawater proliferate explosively or gather highly under specific environmental conditions, causing discoloration of water body. Red tide is a historical name, not necessarily red, but actually a general term for many red tides. According to the causes, types and quantities of red tide, water will appear different colors, such as red or brick red, green, yellow, brown and so on. It is worth pointing out that some red tide organisms (such as Gymnodinium, Gymnodinium, Pyrodinium, etc. Sometimes it doesn't make the sea water appear any special color.