How to judge South American white shrimp algae poisoning, do you know?

In recent years, due to the influence of various factors in the northern coast of the South China Sea, a large number of toxic monocytobarbates have died, resulting in higher and higher algal toxin content in seawater, especially in the inner gulf water. The coastal water ecological environment is seriously polluted, which seriously affects or threatens the health of other marine organisms. The algal toxins produced by red tide kill all kinds of aquatic organisms and are easily certified, but in recent years, poisonous algae have grown and died, and it is not easy to cause large-scale red tides like before. Although the content of algal toxins in seawater is not as high as that of red tide, in the summer and autumn high temperature seasons, toxic algae die every day, and algal poisons in seawater can also accumulate to a certain amount. When coastal shrimp ponds draw seawater with algae poison into the pond, the shrimp farmed in the pond will be poisoned and die in large quantities. Sometimes after the shrimp pond has been cultivated with poisonous algae seeds, the toxins produced can also directly poison the shrimp. In recent years, the shrimp farming industry in the northern coastal waters of the South China Sea has suffered serious losses in summer and autumn due to the impact of algal toxins, and the shrimp farming industry has once again slipped down the trough. At present or for a long time to come, shrimp algae poisoning syndrome will plague the shrimp farming industry, and to revitalize the shrimp farming industry, we must solve this key problem. Therefore, it is imperative to carry out detoxification studies on shrimp algae poisoning.

Poisonous algae species off the northern coast of the South China Sea. There are at least dozens of algae species with toxins along the coast, and the distribution of algae species varies due to different geographical locations, changes in the physical and chemical factors of seawater, climatic conditions and other factors. The types of algal toxins contained in the seawater vary from year to year.

In July, the high temperature season has begun

The poisonous algae species in the South China Sea are more serious to marine life: marine protodioma, micro protodioma, chain alexander algae, tamari Alexander algae, short naked algae, involutefin algae, multi-striated knee groove algae, sickle ring algae, multi-striated rhomboid algae, marine cardinal algae, red tide heteroflora, spherical brown sac algae, biflagellus, toxic Gambian algae, Meeth's nudibranchiae, etc.

Causes of algal toxins

1． Seawater eutrophication

There are four factors that lead to the eutrophication of seawater: the discharge of domestic sewage and aquaculture sewage, the excrement of fish culture in cages, and the nutrient salts converted from the rainwater that brings land, including farmland fertilizer and various trace minerals, into the coast and the seabed, providing sufficient nutrients for the growth and reproduction of algae.

2． antagonism

It-sense substances produced after the secretion or death of certain toxic algae are dominant against non-toxic algae.

3． Advantages of anti-stress

For example, dinoflagellates, when environmental conditions suddenly change or deteriorate, it can become a sac sinking seabed to sleep and wait until the conditions are good to resume normal life, and it is easy to become a dominant population.

4． Meteorological factors

In recent years, the temperature in the northern part of the South China Sea has been significantly polarized, which can be divided into winter cold period and summer hot period. From the beginning of November to the end of March of the following year, the temperature is low, and the temperature is high from April to October every year, and when the Qingming Festival is transformed, a large number of poisonous algae adapted to low temperature growth die and produce a large number of toxins.

5． Radiation action

In the past, the radiation of ultraviolet rays to seawater was about 5m deep in the light layer of seawater, which had a killing effect on the algae in this depth of seawater. At present, due to the destruction of the atmospheric ozone layer, ultraviolet rays can reach more than 10 meters or deeper in the water layer, killing algae, the floating of algae, the movement of sea tides, and the deep algae on the surface. The sea water changes from turbid to clear, providing opportunities for ultraviolet rays to kill algae. The large number of poisonous algae multiplied and died in large quantities, so that the concentration of algal poisons accumulated in the sea water was higher and higher, sometimes reaching the concentration of poisoning some marine organisms, especially in the inner gulf off the coast of the South China Sea.

There are several types of algal toxins

1． Neurotic toxins.

Acts mainly on the nervous system. Neurogenic toxins are present in most of the toxic algae, and their toxic principle is to hinder nerve conduction function and produce disorders. In severe poisoning, it follows the direction of the water flow of the aerator and lacks concentration; when it is mildly poisoned, the movement is sluggish, which is different from the symptoms of advanced dynamic poisoning. Multiple algae species in the dinoflagellate phylum carry a neurotic class of toxins.

2． Hemolytic toxins

Mainly destroys the gastrointestinal tract of shrimp. After poisoning, the rectum becomes significantly thicker and then curved, with symptoms of enlarged liver and pancreas. There are a large number of deaths from severe poisoning, and the intestines of mild poisoning are still curved after swelling. Many algae species with hemolytic toxins also carry a neurotic toxin, which together poison shrimp, aggravate symptoms and increase the difficulty of treatment.

3． Coagulation toxins

It is generally poisoned by shrimp in combination with neurotoxins. After poisoning, the shrimp intestine shrinks, a large number of deaths are severely poisoned, and the intestinal shrinkage of mild poisoning cannot be eaten. The energy needed by shrimp comes from the transformation of the endoplasm of the liver and pancreas, and the endoplasm of the liver and pancreas is exhausted into a skin sac, and the shrimp dies. This diseased shrimp dies partly when it rains, and less dies on sunny days after rain. You can't think that you can use any good medicine, this shrimp has no breeding value, because on a rainy day, the shrimp dies again.

4． Mucus toxins

After a large number of poisonous algae die, cells rupture begins to produce venom mucus, which can directly damage the parotid valve epidermal cells of shrimp, cause swelling, inhibit the gas exchange of shrimp gills, and cause shrimp to die of hypoxia.

5． Carbon chloride

Carbon chloride is a toxic chemical converted by the combination of phytoacic acid and chloride of dead algae, and it exists at the bottom of low-level ponds with poor drainage, in black sand, and where dead algae accumulate. Carbon chloride is a carcinogen that can destroy the shrimp cell endoplasmic coarse reticulopolymeric polysaccharide, hinder the synthesis of proteins, slow down the growth rate of shrimp, and cause chronic death due to severe poisoning.

6． Oxygen radicals

It is present in a variety of algal poisons. High concentrations of oxygen free radicals accumulate in the parotid cells of shrimp and can interfere with the exchange of oxygen. Oxygen free radicals can disrupt fatty acids, amino acids, and impair protein synthesis, so shrimp grow slowly.

7． Unknown toxins

There is an algal toxin that can produce irregularly shaped small white dots under the skin of shrimp, with a diameter of about one millimeter, affecting the peeling of shrimp, and shrimp farmers are commonly known as flower spot disease. This condition is more common in the pools of black filament algae and abnormal cyanobacteria.

(Source: Oceans & Fisheries)