QINGDAO, June 12 (Xinhua) -- Chinese oceanologists said Monday that they have invented an index to predict scale and severity of coastal algae blooms, or "green tides", for up to 40 days.

The index was developed by scientists from multiple research institutes led by the Institute of Oceanology under the Chinese Academy of Sciences. It was based on study on the algae that appeared in the Yellow Sea over the past decade.

Leader of the project Sun Song said the index takes into consideration the amount of algae observed in shallow water, temperature, nutrients, wind, among other factors.

He said the index would help predict a green tide about a month in advance and give authorities more time to react.

An algae bloom develops by absorbing nitrogen and phosphorus pollutants in sea water. It is also be driven by temperature changes.

Though algae is not poisonous, it can block sunshine and consume large amounts of oxygen, suffocating marine life. A large algae bloom can also choke shipping channels and create a bad odor if washed ashore.

Green tides first emerged in the Yellow Sea in 2007. Since then, they have occurred nearly every summer.

The scientists say a new algae bloom has formed this year, but it is small compared to previous years.