Qingdao urges joint efforts to tackle sargassum outbreak

The Qingdao National Laboratory for Marine Science and Technology holds a seminar in June, 2017, to try to predict how algae blooms are going to develop in the Yellow Sea this year. [Photo provided to China Plus]

Along the coast of China's Shandong Province, the Yellow Sea has been turning green.

It's been happening for the best part of ten years during the Summer months. The color is due to a thick carpet of algae called Enteromorpha.

But recently, experts have noticed a decline in the scale of the invasive weed. Instead, the arrival of another kind of floating algae named sargassum poses a potential new threat to the marine environment.

CRI's Yu Yang explains.

Locals in Shandong have become used to the thick coating of Enteromorpha, or Green Sea Lettuce along their shores. The towns of Qingdao and Rizhao have been especially hard hit. Local officials haul it away by the truck load. While it's harmless to humans, as it decomposes, it releases hydrogen sulfide gas, and leaves the area smelling of rotten eggs.

The Qingdao National Laboratory for Marine Science and Technology has teamed up with a number of organizations, such as the Institute of Oceanology of the Chinese Academy of Sciences, the Ocean University of China, and the First Institute of Oceanography of the State Oceanic Administration, to analyze the causes of the algae.

Yu Rencheng is a researcher with the Institute of Oceanology of the Chinese Academy of Sciences.

"The green tide mainly comes from the shoal sea area of northern Jiangsu, spreading by attaching itself to rafts and eventually turning into a floating state. Then starting from the shoal sea area of northern Jiangsu, the green tide slowly expands into the Yellow Sea."

In 2016, the Qingdao National Laboratory for Marine Science and Technology launched a special program to monitor and prevent the successive outbreaks of these green tides and other ecological disasters in China's coastal areas.

As part of the program, the experts proposed a "Green Tide Index" as a means of helping to predict the extent of the problem in the Yellow Sea.

The index includes such elements as the number of micro-reproduction of enteromorpha in the shoal sea area, and the biomass of the algae on the rafts, as well as that of the floating green weed in the shoal sea area. Environmental parameters such as nutrient salt in the sea area, temperature, the strength of the wind and wind direction, all contribute to the index and assist with the follow-up work.

It's hoped by using such a "Green Tide Index" it will be possible to predict the scale of the green tide, 30 to 40 days before it takes shape. Such an early warning will be vital in any comprehensive prevention and control efforts.

Sun Song, a researcher at the Institute of Oceanology at the Chinese Academy of Sciences, is another expert involved in this program.

"In the past, when we discussed prevention and control, we could only fly a satellite remote sensing aircraft to examine where the green tide had arrived. Later, several fishing boats would be organized for clearing it. Now the efforts in prevention and control can be taken in advance. The earlier it is, the more prepared we will be. We'll be clear about how much human labor and resources should be involved, and which location should be given priority in tackling the green tide. Now predictions can be made 30 to 40 days in advance. If it was made a year or half a year in advance, we would be even more ready to deal with the green tide. However, much more effort is needed to achieve this goal."

In June, 2017, the Qingdao National Laboratory for Marine Science and Technology held a seminar predicting the development trend of the green tide of Enteromorpha in the Yellow Sea this year.

A report on the latest research results was released during the event. It suggested the overall scale would be significantly smaller than last year. The biomass of the floating green algae will decrease by more than a half compared with that of the previous years.

Researcher Sun Song explains the possible reasons for the decline:

Firstly, it is the climate issue. Secondly, the growth of sargassum is particularly vigorous this year. Sargassum and enteromorpha are competitive. Thirdly, the changing mode of production has something to do with the trend. This year, when laver seaweed was harvested, enteromprpha was collected at the same time. Only a little sticking to the boom cables was thrown back to the sea. Additionally, the number of the rafts that were travelling into the sea saw a decline."

While the amount of enteromorpha algae was reduced, a new problem with Sargassum emerged.

According to both onsite investigations and remote sensing analysis conducted this year, there was a large amount of sargassum floating in the southern Yellow Sea and East China Sea. Both the marine areas are in the neighborhood of the shoal of northern Jiangsu province. Sargassum accumulated on rafts, causing great damage to the shoal raft culture. The amount of sargassum drifting to the southern part of Yellow Sea was large. Close attention is being paid to the effects it will have on the local aquaculture, environment and ecology.

Sun Song explains:

"On one hand, if sargassum floats close to the shore, it may spawn a secondary disaster that increases the negative impact on aquaculture. But on the other hand, if we get it out of the water in time, sargassum can be processed into bait for other cultured organisms."

The team of researchers involved in this program is now organizing on-site investigations to follow the development of both enteromorpha and sargassum floating in the Yellow Sea area. They want to explore especially where sargassum comes from.

Zhou Mingjiang, a researcher of the Institute of Oceanology of the Chinese Academy of Sciences, offered his observations:

"We haven't studied the golden tides formed by sargassum yet. How did it drift here? It is certain that sargassum came from somewhere else and drifted here with tidal currents. But where did it come from? Was it from the south, the provinces of Zhejiang and Fujian or further regions? It remains unclear as yet."

According to Yang Hongsheng, a researcher from the Institute of Oceanology of the Chinese Academy of Sciences, after a decade of overwhelming enteromorpha, people shouldn't be panicked by a new attack of golden tide. The experts suggest falling back on the previous experience of tackling enteromorpha, and dealing with the new threat with a combination of early warnings, monitoring, and refloating.

"Things are looking up for now. So long as enteromorpha can be taken out of water, it's under control. Sargassum is better than enteromorpha. I breed sea cucumbers. I know sargassum can be a fantastic foodstuff in aquaculture. We are still considering the ways to grow it, since it is difficult for us to grow sargassum ourselves, so I think the flourishing of sargassum is not a bad thing. We could harvest sargassum in order to make use of it in building an ocean pasture on a larger scale. So far, there are two things to be done. Firstly, we need to understand clearly how the sargassum and golden tide will develop. Secondly, we need to know how to better refloat and take advantage of these green and golden seaweed tides."

On the basis of a comprehensive study-and-analysis of the formation and development of these tides in the Yellow Sea, the research teams have put forward prevention and control strategies accordingly.

These experts also believe regional cooperation and joint efforts are needed to turn a potential secondary disaster into an advantage that is conducive to selective breeding in aquaculture.

For CRI, I'm Yu Yang.