The increase in ocean areas without animal or plant life, to 700 in 2019 from 400 in 2008, is one of the conclusions of the second World Ocean Assessment, conducted by hundreds of scientists from around the world and presented by the Secretary-General in a video message.
"Experts attribute (the increase in "dead zones" in the seas) to our widespread failure to achieve integrated sustainable coastal and ocean management," Guterres said.
"I call on all stakeholders to heed this and other warnings. A better understanding of the ocean is essential," he said.
The US ocean agency (NOS) defines maritime "dead zones" as lacking the oxygen needed by most marine life, which either dies or leaves them, creating "biological deserts" at sea.
The report also indicates that about 90 percent of species of mangroves and other coastal and marine ecosystems, as well as more than 30 percent of seabird species, also face extinction threat.
Following an initial report published in 2015, the World Ocean Assessment points to continued degradation of coastal and marine spaces due to human action.
"Pressures from many human activities continue to degrade the oceans and destroy essential habitats - such as mangroves and coral reefs - hampering their ability to help cope with the impacts of climate change," Guterres said.
"These pressures also come from land-based and coastal human activities, which bring dangerous pollutants into the oceans, including plastic waste," he said.
The UN secretary-general stressed that the release of carbon dioxide is accentuating the warming and acidification of sea waters, destroying biodiversity, while rising sea levels damage coastal areas, and the depletion of fish stocks due to over-exploitation generates an estimated annual loss of $88.9 billion.
"As the Assessment makes clear (...) we need to better integrate scientific knowledge and policy-making," Guterres stressed.
This year marked the start of the United Nations Decade of Ocean Science for Sustainable Development and a series of international events related to the environment and climate are, according to Guterres, an opportunity to reverse course.
"The findings of this Assessment underline the urgency of ambitious outcomes at UN summits and high-level events on biodiversity, climate and more throughout this year," he added.
"Together, we can promote not only a green - but also blue - recovery from the Covid-19 pandemic and help ensure a resilient and sustainable long-term relationship with the ocean."
Guterres is one of the personalities who will speak at the virtual summit on the climate crisis on 22 and 23 April hosted by US President Joe Biden.
Chinese President Xi Jinping will also attend the summit, despite the decline in relations between Beijing and Washington, China's foreign ministry said on 21 April.
The Chinese head of state will deliver an "important speech" via video conference from Beijing, the ministry revealed, just days after the two countries pledged to "cooperate" on climate change.
China and the United States are the two biggest emitters of greenhouse gases, the source of global warming, and the agreement between the two countries is therefore seen as crucial to the success of international efforts to reduce emissions.