Definition. The normal concentration of sodium in the blood plasma is 136-145 mM. Hyponatremia occurs when sodium falls below 130 mM. Plasma sodium levels of 125 mM or less are dangerous and can result in seizures and coma. Description. Sodium is an atom, or ion, that carries a single positive charge.
reef1. 1  a ridge of rocks or sand, often of coral debris, at or near the surface of the water. 2  Mining. a lode or vein.
The Great Barrier Reef is the largest coral reef system on the planet and is one of the Seven Wonders of the World. The Great Barrier Reef is both a Marine Park and a listed World Heritage site, and is the only structure built by a living community on earth that can be seen by the naked eye from the moon.