STORY: About 7,000 people are expected to attend the U.N. Ocean Conference in Lisbon, including heads of state, scientists and NGOs, to assess progress in implementing a directive to protect marine life.
"Sadly, we have taken the ocean for granted, and today we face what I would call an 'ocean emergency'," Guterres told the conference. "We must turn the tide."
Guterres said there was a need for symbiotic business models that could help the ocean produce more food and generate more renewable energy.
The ocean covers about 70% of the planet's surface, generating 50% of the oxygen and absorbing 25% of all carbon dioxide emissions.
But climate change is pushing ocean temperatures to record levels and making it more acidic, he said, adding that some eight million tons of plastic waste enter the oceans each year.