Magnesium

Magnesium is the eighth most abundant natural element on earth and is a common component of water. Magnesium is found in many geologic formations, including dolomite. It's an essential nutrient for all organisms and is found in high concentrations in vegetables, algae, fish, and mammals. Magnesium is represented in the Periodic Table of Elements as Mg.

The Role of Magnesium in Waterbodies
Natural sources contribute more magnesium to the environment than do all human activities combined. Magnesium is found in algal pigments (known as chlorophyll) and is used in the metabolism of plants, algae, fungi, and bacteria. Freshwater organisms need very little magnesium compared to the amount available to them in water. Because there is such little biological demand for magnesium compounds and because they are highly soluble, magnesium concentrations in waterbodies fluctuate very little.

Elevated (high) magnesium concentrations can cause water to be designated as "hard" water. (Elevated calcium concentrations can have the same effect.) When hard water is used for agricultural, domestic, and industrial purposes, a crusty mineral buildup called "scale" can form and cause problems. The scale produced by extremely hard water can clog irrigation lines and water pipes in houses and can reduce the efficiency of hot water heaters.

In Florida
Waterbodies in the Florida LAKEWATCH database had average magnesium concentrations ranging from 0.02 to over 600mg/L. Magnesium concentrations are higher in waterbodies where inflowing water has been in contact with dolomite.

Health Concerns
Magnesium causes no known human health problems. Drinking large amounts of hard water when the body is accustomed to soft water, however, may have a laxative effect.

See also:
Calcium (for a description of hard water)

The information on this page was derived in part from the following publication of
Florida Lakewatch of the University of Florida Department of Fisheries and Aquatic Sciences.
This booklet may be downloaded in its entirety as a PDF file by clicking here.
Scroll down till you see the Circular 101 icon.

Vic Ramey is the editor.

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A collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Invasive Plant Management Section of the Florida Fish and Wildlife Conservation Commission.