Did you see or notice that black gunk in the bay recently? 

Many people were concerned, including worries this was some sort of oil spill. Acccording to local marine experts; however, this is an ecological anomoly, with the results of recent tests claiming it's harmless.

On May 3, Shenzhen marine monitoring and forecasting center issued a notice saying: a red tide occurred in the sea area of Shenzhen Bay. The monitoring showed that it was a non-toxic red tide, and there were no fish deaths. Over the next few days, the center continued to track and monitor the sea area.


According to the field observation, the sea water in the red tide sea area is light reddish brown, distributed continuously in the sea area of Shenzhen Bay (113 ° 56'56.79 "E, 22 ° 29'1.40" n). The red tide area is 6 square kilometers, and no fish death is found.

The results showed that the average cell density of the dominant species was 6.7 × 106 cells / L, and that of the sub dominant species was 2.2 × 106 cells / L, all of which were non-toxic; the pH value of seawater was 8.63, the dissolved oxygen was 12.72mg/l; the temperature and salinity of seawater were normal, 26.61 ℃ and 17.69 ℃, respectively.

01 What is red tide?

Red tide: also known as algal bloom, is a kind of ecological abnormal phenomenon that causes the local water body to change color due to the explosive proliferation or high aggregation of some phytoplankton, protozoa or bacteria in the water body under specific environmental conditions.

According to the variety and quantity of red tide, water body will present different colors, such as red or brick red, green, yellow, brown, etc., but some red tides sometimes do not cause color change of sea water.

02 What are the hazards of red tide

◆ biological toxins produced by red tide organisms are transmitted to other animals and human bodies through the food chain, resulting in poisoning or even death.

◆ harm of red tide to marine ecological environment:

(1) The mucus secreted or produced by the red tide organism adheres to the gills of marine animals such as fish and blocks the respiratory system, resulting in asphyxiating death;

(2) When the red tide organism decays, it consumes a lot of oxygen in the water body, which leads to the lack of oxygen in the water body or the accumulation of a large number of hydrogen sulfide and methane, which causes the marine organism to die of anoxia or poisoning;

(3) A large number of red tide organisms gather on the surface of the sea water to block the sunlight, reduce the transparency of the water body, and affect the survival and reproduction of other marine algae and animals growing in the deep layer of the water body;

(4) The competition of red tide for nutrients in water results in the increase of biomass, but the decrease of species;

(5) Red tide leads to the destruction of coastal beach environment and the closure of beaches.

◆ Red tide can have harmful effects on human health if toxins are ingested, and may also cause skin infection or irritation to eyes and respiratory tract if coming into contact.

资料图  图源:视觉中国

Source: http://深圳湾海水变“赤红色”,现不明漂浮物!官方通报

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