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 on Earth. A barrier reef is a long, narrow coral formation that lies parallel to the shoreline of a landmass and is mostly underwater. The Great Barrier Reef is in the Coral Sea, off the northeastern coast of Australia. It extends 1,250 miles (2,000 kilometers) from north to south. In the Coral Sea, off the coast of Queensland, Australia, lies the Great Barrier Reef, one of the natural wonders of the world. A barrier reef is a long, narrow, mostly submerged coral formation that lies parallel to the shoreline of a landmass.