A red tide is a dense population of aquatic microscopic organisms that breed in the abundance of salt in surface water. The micro-organisms appear in most of the world's waters and most are harmless. However, some single-cell organisms produce a poison that paralyzes and kills fish. These organisms may also suffocate the fish by consuming nearly all the oxygen in the water. Specialists say that the red tide is mainly caused by pollution from land and the large-scale farming in coastal waters, which produce too much nitrogen and phosphorus.
Statistics show that the frequency of red tides along China's coastal areas is climbing.
From 1993 to 1997, a total of 265 red tides were reported in Chinese waters. More than eight billion tons of pollutants are released into China's coastal areas every year. In addition, geologists note that excessive reclamation of land from marshes has also damaged the ocean ecology and is yet another factor leading to the increasing occurrence of red tides.