The 193 UN member nations have issued an urgent call for action to reverse the decline in the health and productivity of the world's oceans.

Ministers and diplomats burst into applause as the final document was gavelled to approval by consensus at the end of the first-ever UN conference on oceans.

It recognises the critical importance of the world's seas to the future of the planet: Covering three-quarter of the Earth, they supply nearly half the oxygen that we breathe, absorb over a quarter of the carbon dioxide we produce, provide food, and play key roles in water cycles and the climate system.

The government leaders called on people and organisations everywhere to take action to reverse the threats from plastic garbage, illegal and excessive fishing, rising sea levels that could wipe out small islands, and increasing acidity of ocean water that is killing marine life.

While the call for action was unanimously approved, countries are allowed to express reservations afterwards.

Egypt and Russia also dissociated their governments from specific provisions, but the United States was the only country to oppose the Paris accord. And when France and the European Union spoke after the US and urged implementation of the climate deal, they received loud applause.

US deputy assistant secretary of state David Balton, who is in charge of oceans and fisheries, noted President Donald Trump's announcement on June 1 that the United States will withdraw from the Paris agreement or renegotiate US participation, which has already been rejected by other countries.

But Mr Balton said the US remains committed to work inside and outside the UN to address "threats to the ocean and to promote its conservation and sustainable management for this and future generations".

General assembly president Peter Thomson, a veteran diplomat from Fiji, said his goal for the five-day conference was to start the reversal of the decline of the oceans.

"I am 100% satisfied," he said. "From this point onward nobody can say they are unaware. The bar has been raised on global consciousness and awareness."

Mr Thomson stressed when asked why there was no serious fighting over the call for action that the ocean is the common heritage of mankind and restoring its health is a great challenge of our time.

"If it's dying, it's dying on all of us," he said. "When it comes to the ocean there's no them and us. It's all of us or nothing."

The call for action, while not legally binding, urges all "stakeholders" to take a series of urgent actions to heal the oceans.

These include reducing the use of plastics and invisible micro-plastics such as plastic bags and containers that are discarded after a single use, developing and implementing measures to reduce acidification of the oceans, and combating rising sea levels and increasing ocean temperatures.

A 2016 World Economic Forum report said the best research estimates there are over 150 million tons of plastics in the ocean. "In a business-as-usual scenario, the ocean is expected to contain one ton of plastic for every three tons of fish by 2025, and by 2050, more plastics than fish (by weight)," it said.

Other actions the governments urged include measures to protect coastal ecosystems such as mangroves and coral reefs, and to "end destructive fishing practices and illegal, unreported and unregulated fishing" and restore fish stocks "in the shortest time feasible at least to levels that can produce maximum sustainable yield".

In 2015, world leaders adopted new UN goals for 2030 including on conserving and managing the ocean's resources.

Sweden's deputy prime minister Isabella Lovin, the conference co-chair, said over 1,200 commitments were registered by countries, organisations and the private sector - and more were expected.

Many countries announced steps to reduce or eliminate the single use of plastics and stepped up efforts to reduce the amount of sewage and pollution entering the ocean. Many commitments focused on expanding scientific knowledge about the ocean, and there were new commitments on fishing including "no-take zones" for certain species and measures to combat illegal fishing.

The UN said the commitments indicate "the world is well on track to protect over 10% of the globe's marine areas by 2020," citing announcements during the conference that add 4.4% of marine areas to the existing protected list.