Blue-green algae

Deterioration of pond bottom or accumulation of organic materials leads to the faster development of blue-green algae bloom than green algae. Blue-green algae such as Oscillatoria, Phormidiu, Microsystis and Microcoleus dominate (accounting for 90%). Although the survival rates in ponds with this colour still remains high, the growth rate sinks. So, the growth of blue-green algae is undesirable and should be remove from shrimp ponds.

Blooms of certain filamentous blue-green algae, all belonging to the family Oscillatoriaceae, have been implicated as causing the Hemocytic enteritis (HE) disease syndrome in primarily young juvenile penaeids. The principal lesion of HE, which occurs as the result of algal endotoxin released in the gut from ingested algae, is a necrosis and marked hemocytic inflammation of the mucosal epithelium of the midgut and its caeca, accompanied by necrosis and degeneration of the hepatopancreas. The cause of death in shrimp with HE may be due to osmotic imbalances, poor absorption of nutrients, or to secondary-bacterial infections. Species of Vibrio, usually V. alginolyticus, are the organisms most commonly isolated from the septic hemolymph of shrimp with HE. Runting of shrimp affected with HE is apparently due to midget disfunction and to the length of time required for the midgut mucosa o regenerate and is a chronic effect in animals that survive the disease.