The offshore and coastal zones in Zhejiang, Liaoning, Guangdong and Fujian provinces are the ones with frequent red tides, mainly affected by inorganic nitrogen and phosphate.

• 浙江、辽宁、广东、福建等近岸、近海海域为赤潮多发区。赤潮频繁发生海域多为受无机氮和磷酸盐污染较重的海域。