On June 28, Green Society volunteers found large-scale cyanobacteria outbreaks in the Shenqiu section of the Shaying River, the largest tributary of the Huai River, and some sections of the river have formed large blue-green blooms, causing the death of some aquatic organisms.
Image Source/Volunteer
"From the visual point of view, the cyanobacteria in these sections of the river are in the outbreak period, the color of the water body from light green to thick green, within a few days has been viscous and can not be opened, there are many bubbles piled up on the surface of the water, the naked eye can see that the density of algae is increasing rapidly day by day", The green society volunteer Teacher Huo has been tracking and investigating on the bank of the Shaying River for several consecutive days, determining the main river section of the cyanobacterial outbreak, distributed within the 15-kilometer river section from Xiangcheng to the Huaidian Gate in Shenqiu County, and the current situation is that the dot flakes are erupting.
"From the initial discovery of the bloom phenomenon, to the current proliferation of cyanobacteria, the water body has become thick green, and even the surface of the water has peeled and scaled, the whole process has been emitting odor," Mr. Huo described.
Cyanobacterial outbreak taken in mid-June Image source/volunteer
At the end of May, when the cyanobacteria in the Shaying River had not yet erupted on such a large scale, Green Society volunteers had noticed the death of river mussels in this section of the river. These dead river mussels float on the nearshore water, and the mussel meat is clearly separated from the mussel shell. Since the river mussel itself is a benthic filter-feeding organism, Teacher Huo is worried that during the feeding process, it was poisoned by microcystins emitted by cyanobacterial outbreaks and died.
The death of the Shaying River mussel photographed by volunteers on May 23 Image source/volunteer
On May 23, volunteers photographed the death of the Shaying River mussel
Cyanobacteria, a single-celled algae organism, also known as blue-green algae, was first seen on Earth, about 3.5-3 billion years ago, and was a prokaryotoid like bacteria. At present, there are about 2,000 species of cyanobacteria known to the scientific community, and about 900 species have been recorded in China, and cyanobacteria are widely distributed all over the world, but most of them appear in freshwater and a few in seawater. Because different cyanobacteria contain different pigments, such as chlorophyll, cyanophyll, algalrubin, etc., their appearance color is not all blue or blue-green. However, cyanobacteria outbreaks, for water quality such as rivers and lakes, are inseparable from eutrophication of water bodies, and are a water quality marker species, which mostly multiply in large numbers in summer.
According to the locals in Shenqiu, the cyanobacterial outbreak in the Shaying River section of the Huai River first appeared in 2014, and then there were cyanobacterial outbreaks for four consecutive years, but they did not appear in 2018, and there were serious cyanobacterial outbreaks again in 2019-2020 and this summer.
"This year is the third consecutive year of outbreaks, although the water quality of the Huai River has generally improved in recent years, but the original pollution source treatment is not complete, especially the large number of rural black and odorous water bodies are secretly discharged, most of them take advantage of the opportunity of rainfall to flow directly into the Huai River", Green Society volunteers believe that the failure to cure the complete rural black and odorous water bodies is likely to be one of the important reasons for the continuous cyanobacterial outbreak in the Shaying River and the Huai River in recent years, while the fish in the water are overfished, and the imbalance of the water ecosystem is also another important reason for the outbreak of cyanobacteria.
"If it is allowed to develop, it is very worried that it will affect the Hongze Lake further downstream, and the algal toxins emitted by the next larger cyanobacteria outbreak, which may also cause the death of a large number of aquatic organisms in the river again", Green Society volunteers hope that the relevant local departments can quickly take measures to carry out comprehensive water treatment in the cyanobacteria areas that have erupted in the Shaying River section, such as intercepting and purifying the rural sewage along both sides of the river, and implementing a long-term fishing ban for 5-10 years on the Shaying River and the Huai River section.
Relevant studies have confirmed that the green tide caused by large-scale cyanobacterial outbreaks will exacerbate the further deterioration of water quality, and when severe, it can exhaust oxygen in the water and cause aquatic life to die, and about half of the current cyanobacteria species can emit microcystins, forming microcystins released after the formation of green tides, which is an important cause of liver cancer. Therefore, the World Health Organization (WHO) has used this toxin as one of the criteria for the determination of drinking water quality.
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