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 world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi).The reef is located in the Coral Sea, off the coast of Queensland, Australia.The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps.he reef is located in the Coral Sea, off the coast of Queensland, Australia. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms.