U.S. President Barack Obama will address the summit Monday in a video message to announce the creation of two new U.S. marine sanctuaries in the states of Maryland and Wisconsin.
Other countries are also expected to announce similar moves.
U.S. Secretary of State John Kerry is attending the conference.
Several countries and foundations are set to pledge funds and propose initiatives to fight pollution, overfishing and the acidification of the ocean by carbon emissions.
The U.S. is also expected to announce a plan, called Sea Scout, designed to bring a halt to the world's illegal and unregulated fishing trade.
Chilean President Michelle Bachelet and Foreign Minister Heraldo Munoz will also speak at the conference.