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.
Reefs (aka Rainforest of the Sea) : Reefs are made of coral or rocky formations. Coral reefs are one of the most diverse marine habitats. Coral reefs are most commonly found at shallow depths in tropical waters, but deep water and cold water corals also exist on smaller scales in other areas.