Marine Biology

Salinity

It is an important factor that restricts coral reef development. Hermatypic corals are true marine organisms and are intolerant of salinities deviating significantly from that of normal seawater (32 - 35 ppt). Wherever inshore waters are subject to continuing influxes of freshwater from river discharge so that the salinity is lowered, reef will be absent. Such is the case along large portions of the Atlantic coast of South America, where the Amazon and Orinoco rivers discharge a huge volume of freshwater, and reefs are absent. On a smaller scale, this occurs in many areas of the tropics where rivers and streams discharging freshwater into the sea cause breaks in reef development. However, on the other hand, coral reefs do occur in regions of elevated salinity, such as the Persian Gulf, where reefs flourish at 42 ppt.