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Such is the situation that in 2016 the United Nations’ Intergovernmental Oceanographic Commission set up the Global Ocean Oxygen Network (GO2NE), comprising a team of scientists from around the world to search for solutions. Dr Yasuhara was asked to join the team and contribute his expertise as a paleoecologist, specialising in oxygen in historical and geological records.

“Paleoecology relating to oxygen was part of my thesis,” said Dr Yasuhara. “The decline in ocean oxygen ranks among the most serious effects of human activities on the marginal marine environment, and the Asian coast including Hong Kong is one of the most seriously effected.”

In early 2018, GO2NE produced its first paper revealing the network’s findings on the causes of oxygen deprivation, and offering solutions on how to raise oxygen levels. The report, which was published in the journal Science, was unique in that it covered both the open ocean and coastal waters.

Among its worst discoveries was that the amount of water in the ocean containing near zero oxygen has increased more than four-fold in the last half-century. The scientists said they expect those oxygen levels to keep dropping, both as the Earth continues warming and because of eutrophication, which is when run-off from the land leads to excessive richness of nutrients in water causing dense growth of plant life. Since 1950, low oxygen sites in coastal water bodies, such as estuaries and seas, have increased more than 10-fold.

Dead zones

“Clearly, this is not good news, but methods to alleviate the problem are relatively straightforward,” said Dr Yasuhara. “We need to address the issues which are causing oxygen levels to fall, namely climate change and nutrient pollution in our oceans. It is a combination of these two factors which increases what we refer to as dead zones, that is, places where the oxygen levels are too low to support marine life. Quite simply marine animals suffocate and die and fish avoid the areas.”

The Asian coastline is particularly bad because of the fast industrialisation of the area. Europe and the US had their industrial revolutions 200 years ago, but in Asia it has occurred in the last 50 to 100 years. Many countries in the region have begun developing relatively recently and very rapidly this century.

Around Hong Kong, the waters are suffering especially because of rapid industrialisation and the sheer density of the population, meaning a relatively small area produces a lot of waste and pollutants. “Across Southeast Asia things could be dying out in the waters around us at a rapid rate,” said Dr Yasuhara. “For the US and Europe it has been a long-term problem, and there has even been some improvement recently as there is more regulation and awareness there.”

On the plus side, he feels that Hong Kong could be a leader in instigating a drive to improve the situation in Asia. “In Hong Kong there is a good sense of what needs to be done to achieve conservation. NGOs work hard here and the younger generation is very aware. Hong Kong could take the lead in Asia on environmentally-friendly production and reducing waste, as well as cleaning up the oceans.

“Another problem in the wider Southeast Asia region is that there is not enough research, so we do not have enough information. In some countries data may exist but it is difficult to access – although sometimes that is simply the result of language barriers as there are many different languages in Asia. It’s important to have better data across the globe. At the moment the US and Europe – the northern hemisphere – have good data, but Southeast Asia does not.

“As paleoecologists, we learn from history – we examine at the characteristics of ancient environments and their relationships to ancient lives. It is looking to the past to learn about the future. We need to find answers to how oxygen, or the lack of it, changes the marine ecosystem and biodiversity, how it is associated with long-term climate change and how it effects other things such as the acidification of our waters.”

GO2NE’s report has attracted much attention, and been published or aired by more than 300 media organisations around the world. Dr Yasuhara said it is a major first achievement for the newly-formed group and the hope now is that governments will respond to the findings and introduce measures to reduce waste and improve water treatment.


Oxygen in Oceans
Takes a Dive

The health of our oceans is facing threats on multiple fronts. One of the most serious is oxygen deprivation, which could devastate marine life and biodiversity. Marine biologist
Dr Moriaki Yasuhara is part of an international team looking to find a solution.


We need to find answers to how oxygen, or the lack of it, changes the marine ecosystem
and biodiversity, how it is associated with
long-term climate change and how it effects other things such as the acidification of
our waters.

Dr Moriaki Yasuhara



Low oxygen caused the death of these corals and others in Bocas del Toro, Panama. The dead crabs pictured also succumbed to the loss of dissolved oxygen.

(Courtesy of Arcadio Castillo/Smithsonian)

Low-oxygen zones are spreading around the globe. Red dots mark places on the coast where oxygen has plummeted to two milligrams per litre or less, and blue areas mark zones with the same low-oxygen levels in the open ocean.

(Courtesy of GO2NE working group. Data from World Ocean Atlas 2013 and provided by R J Diaz)

Members of the Global Ocean Oxygen Network (GO2NE) working group in Monterey, USA.

(Courtesy of Francisco Chavez)