The Amazon, Nile and Mississippi are mighty rivers, but they and all their worldwide brethren might be a relative trickle compared with an unseen torrent below the surface. New research shows that rivers might constitute as little as 20 percent of the water that flows yearly into the Atlantic and Indo-Pacific Oceans from the continents. The rest flows through what is termed the 'subterranean estuary,' which some researchers think supply the lion's share of terrestrial nutrients to the oceans....