In what would be its largest grant to date, Ted Turner’s U.N. Foundation is proposing to give $10 million to preserve the world’s coral reefs. The foundation’s board is meeting tomorrow to vote on the grant, which would go to the International Coral Reef Action Network, a coalition of academic, private, and intergovernmental groups led by the U.N. Environment Programme. The money would be spent over four years to address such threats to coral reefs as overfishing, coastal development, and marine pollution. Projects in the Caribbean and the eastern coast of Africa would receive the first attention.