Red tides have appeared around Haiphong City’s Cat Ba Island since late March 2012, triggering concerns about their harmful effects on the environment.

Red tide in Cat Ba

The Seafood Research Institute said the phenomenon is a result of accumulations of an alga, Noctiluca scintillans.

Even though such kind of alga does not create toxics, they are able to accumulate high levels of ammonia. When the algae are present in high concentrations, it will result in the depletion of oxygen in the water, the institute warned.

The combination of these two effects may kill aquatic creatures.

According to the institute, the current accumulation of these algae is still at acceptable levels but further oversight is needed as they may continue to plague the area in the time to come.

Bui Trung Nghia, Chairman of Cat Hai District People’s Committee, told DTiNews that the algae grew on a small scale over recent days, and was yet to cause any problems to local fishing.

However, local residents should be aware of the possible harmful effects of the incident in order to take preventive measures and ensure the safety to their fish farming areas, Nghia added.

Red algae near a cliff

Red tides could result in the depletion of oxygen