The Chinese city of Qingdao is under attack from green algae. The city’s waterways have been covered under a heavy layer of green algae, sometimes called the ‘green tide’. The algae bloom has already covered 1,700 km² of coastline for over two weeks. The issue is similar to the ‘sea snot’ crisis that struck Turkey earlier in the year, and is still overwhelming the Sea of Marmara.

The ‘green tide’ has been an annual issue for the Eastern port city of Qingdao. But the problem seems to be getting worse each year.

What is the ‘green tide’ and what causes it?

The green tide is essentially a rapid increase in the population of green algae found in the water naturally. As the population of green algae increases, the algae begin to accumulate in large blanket-like layers that float on top of the water’s surface. These blankets are then carried by water currents and accumulate near the coast and banks.

Algae blooms are caused by a variety of factors. These include available nutrients, temperature, sunlight, ecosystem disturbance and others. As pollutants and wastewater is pumped into water bodies, the temperature and amount of nutrients needed by the algae also increase. This leads to an exponential rise in algae production.

"Green tide can also be regarded as a type of harmful algal bloom. It is also a manifestation of abnormal changes in the ecosystem,” said Yu Rencheng, Research Fellow, Institute Of Oceanology, Chinese Academy Of Sciences.

Dangers of algae blooms

Algae draw oxygen from the water. A large presence of algae in water bodies directly starts to affect the oxygen levels within the waterbody. As oxygen saturation decreases, aquatic life like fish, coral, shellfish, start to die as they’re not able to get enough oxygen.

Aquatic plant life is also affected by the decrease in oxygen and also as the algae bloom starts forming a blanket that blocks sunlight from reaching the sea bed. When algae bloom reaches a critical mass, the layers of algae slowly start spreading towards the water bed as well. This blanket layer starts to drown anything that gets in its way.

Algae blooms can be ecologically devastating as a result.

The ‘green tide’ as it starts to die and decompose, starts to become a breeding ground for dangerous pathogens that can cause severe illnesses. The odour and gaseous by-products of the green tide can also be foul-smelling and toxic.

What is China doing to combat the problem?

The bloom has not yet affected the operations of the Qingdao port, a major hub of petrochemical trade. Over 1 million tonnes of green algae will be scooped up by a fleet of thousands of surface vessels and workers.

While the problem is slowly being dealt with at the moment, it still presents a long-term problem. The ‘green tide’ has continued to arise for the past 15 years, with no signs of abetting. This year’s outbreak was the largest one seen yet.

The Chinese government has invested at least $307.24 million in environmental protection to stem the algae bloom disrupting activities in Qingdao. But as global temperatures rise, and water pollutants continue to contaminate the sea, the ‘green tide’ is expected to not go away soon.

“Therefore, we need to propose some prevention and control strategies based on understanding the mechanisms of green tide. But more importantly, we still have to pay attention to the coastal ecosystem, the impact of human activities on the ecosystem, or some changes in the green tide under the conditions of climate change," said Rencheng.

(Edited by : Anshul)