Hainan Escalates Red Tide Response as Bloom Worsens

Hainan Province raised its red tide emergency response from Level III to Level II on June 30, signaling a significant escalation of a harmful algal bloom (HAB) that has devastated marine aquaculture along the island’s western coastline. The bloom, first detected on June 25, has caused mass fish mortality across Chengmai, Danzhou, Lingao, and Haikou, with economic losses already crossing the tens of millions of yuan threshold.

According to CCTV News, the Hainan Marine Disaster Emergency Response Office upgraded the response on the morning of June 30, triggering enhanced monitoring, stricter fishery regulation, and expanded public safety measures across affected coastal areas.

Context and Background

Red tide, or harmful algal bloom, is an ecological phenomenon where marine phytoplankton proliferate explosively under specific environmental conditions, causing seawater discoloration and ecosystem disruption. Under China’s national Red Tide Disaster Emergency Plan, a Level III (Yellow Alert) response applies to losses between 20 million and 100 million yuan (approximately $2.75 million to $13.8 million USD). The escalation to Level II (Orange Alert) reflects the severity and expanding scope of the disaster.

Hainan’s western coast is a major center for deep-water net cage aquaculture, particularly for high-value species like golden pomfret and cobia. The region is especially vulnerable to red tides during summer months when rising sea surface temperatures create favorable conditions for algal blooms.

Key Developments

The bloom was first detected on June 25 when abnormal seawater coloration was reported off the coasts of Changjiang County, Danzhou City, and Lingao County. By June 26, the affected area had reached a maximum of 187 square kilometers, according to the Hainan Marine Monitoring and Forecasting Center.

The causative organism was initially identified as Pheopolykrikos hartmannii, a dinoflagellate species that produces fish toxins. Subsequent analysis by Professor Lü Songhui’s team at Jinan University, reported by Hainan Daily, suggested the dominant species may belong to the Gonyaulax genus. Researchers are conducting electron microscopy and molecular biology analysis to confirm the exact classification.

The damage to aquaculture has been severe. In Chengmai County’s Yubao Port, over 150 of 220 cobia aquaculture cages experienced mass fish mortality, with approximately 150 metric tons of dead fish recovered. In Danzhou’s Eman Town waters, an estimated 1.5 million golden pomfret fingerlings — roughly 225 metric tons — were lost. Lingao County’s Houshui Bay, with 112 deep-water cages and 20 million golden pomfret fingerlings, continues to compile mortality statistics.

Dead fish also washed ashore at Haikou’s Rongshanliao Beach on June 26, prompting public concern. The local government confirmed the deaths were caused by hypoxia — dissolved oxygen depletion resulting from the algal bloom — and initiated immediate cleanup operations, as reported by Guancha.

Analysis and Implications

Experts have identified several contributing factors to the outbreak: prolonged high temperatures, significant sea surface temperature fluctuations, reduced plankton biodiversity, and the resulting ecological niche occupation by the dominant algal species. The Hainan Agriculture Department has issued comprehensive technical guidelines for aquaculture disaster prevention, including submerging cages below surface red tide concentrations, relocating operations to unaffected waters, and implementing strict dead fish disposal protocols.

Crucially, Professor Lü’s team has confirmed that the toxin produced by the Gonyaulax species, while highly toxic to fish, does not accumulate in shellfish and will not biomagnify through the food chain to humans. This means there is no public health risk from consuming properly inspected seafood from the area, though authorities have strictly prohibited fishing, collecting, or selling marine organisms from affected zones.

What’s Next

Hainan has deployed a three-dimensional monitoring network combining satellite remote sensing, unmanned aerial vehicles, offshore and coastal monitoring stations, and ship-based sampling to track the bloom’s movement. Meteorological departments are predicting drift paths as authorities intensify sampling along the entire western coastline.

The red tide was ongoing as of June 30 with no clear end date. The final economic damage figure remains to be determined, though it has already exceeded the Level III threshold. The event raises broader questions about the increasing frequency of harmful algal blooms in South China’s waters, which have seen multiple red tide events in recent years, including Phaeocystis globosa blooms affecting Fujian, Guangdong, Guangxi, and Hainan in early 2025.