UNITED NATIONS, March 1 (Xinhua) -- The United Nations on Friday raised awareness about the "crucial importance" of marine species to sustainable development on the occasion of World Wildlife Day.

Under the theme of "Life below water: for people and planet" this year, the world day, which falls on March 3, was celebrated at an event co-organized by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), UN Development Programme and UN Environment Programme.

"Marine species provide indispensable ecosystem services. Plankton enrich the atmosphere with oxygen, and more than three billion people depend on marine coastal biodiversity for sustenance and livelihoods," UN Secretary-General Antonio Guterres said in his message to the day, which was read at the event by CITES Secretary-General Ivonne Higuero.

The UN chief noted that marine and coastal resources and the industries they support are estimated to be worth at least three trillion U.S. dollars a year, some 5 percent of global GDP.

He called for sustainable managing and protecting marine and coastal ecosystems, which are the objectives of goal 15 of the 2030 Agenda for Sustainable Development of the United Nations.