Artificial seawater

Artificial seawater (abbreviated ASW) is a mixture of dissolved mineral salts (and sometimes vitamins) that simulates seawater. Artificial seawater is primarily used in marine biology and in marine and reef aquaria, and allows the easy preparation of media appropriate for marine organisms (including algae, bacteria, plants and animals). From a scientific perspective, artificial seawater has the advantage of reproducibility over natural seawater since it is a standardized formula. Artificial seawater is also known as synthetic seawater and substitute ocean water.

Example

The tables below present an example of an artificial seawater (35.00 ‰ of salinity) preparation devised by Kester, Duedall, Connors and Pytkowicz (1967).^[1] The recipe consists of two lists of mineral salts, the first of anhydrous salts that can be weighed out, the second of hydrated salts that should be added to the artificial seawater as a solution.

Anhydrous salts

Salt	Molecular weight	g kg−1 solution
Sodium chloride (NaCl)	58.44	23.926
Sodium sulfate (Na2SO4)	142.04	4.008
Potassium chloride (KCl)	74.56	0.677
Sodium bicarbonate (NaHCO3)	84.00	0.196
Potassium bromide (KBr)	119.01	0.098
Boric acid (H3BO3)	61.83	0.026
Sodium fluoride (NaF)	41.99	0.003

Hydrated salts

Salt	Molecular weight	mol kg−1 solution
Magnesium chloride (MgCl2.6H2O)	203.33	0.05327
Calcium chloride (CaCl2.2H2O)	147.03	0.01033
Strontium chloride (SrCl2.6H2O)	266.64	0.00009

While all the compounds listed in the recipe above are inorganic, mineral salts, some artificial seawater recipes, such as that of Goldman and McCarthy (1978),^[2] also add trace solutions of vitamins and organic compounds needed by marine organisms.

Standard

The International Standard for making artificial seawater can be found at ASTM International.^[3] The current standard code is ASTM D1141-98^[4] (the original standard was ASTM D1141-52) and describes the standard practice for the preparation of substitute ocean water. The ASTM D1141-98 standard is available in a ready-made artificial seawater form or as a "Sea Salt" mix that scientists and hobbyists can prepare. Generally, the ready-made artificial seawater comes in 1 gallon and 5 gallon containers, whereas the "Sea Salt" mix comes in 20 lb pails (makes approximately 57 gallons) and 50 lb pails (makes approximately 143 gallons).

Uses and applications

There are various applications for ASTM D1141-98 synthetic seawater including corrosion studies, ocean instrument calibration and chemical processing.^[5] Typically, laboratory-grade water is used for preparing synthetic seawater.^[6]

See also

• Algaculture
• Aquarium