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.
Great Barrier Reef. The great barrier reef is the worldâs largest individual formation created by living organisms. As the largest coral reef in the world, the Great Barrier Reef includes over 900 islands, over 2,900 separate reefs, and supports one of the most diverse ecosystems in the world.