As an introduction to this article an obligatory question: What is natural seawater? If we leave aside the solid particles, gases and colloidal matter present in marine water, and we concentrate only on the dissolved organic matter, the result may be surprising for a few:

The rather complex name of this article probably best describes the complexity of matters when it comes to seawater buffering capacity in the reefkeeping practice.

Chlorinity, salinity and density are the basic physico-chemical properties of seawater, depending primarily upon the concentration of the following essential constituents of seawater:

Boron occurs in nature exclusively in the form of boron compounds. With an average molar concentration of 4,16.10^-4 mol/l, boron is the eighth most common element in marine water. Expressed in mass units its average concentration is 4,5.10^-3 g/l (4,5 mg/l).

Iodine occurs on Earth exclusively in the form of iodine compounds, primarily diluted in salt-water and freshwater. With an average molar concentration of 4.10^-7 mol/l, iodine is the eighteenth most abundant element in sea water. Expressed in mass units, the iodine concentration ranges between 2,5.10^-5 - 6,4.10^-5 g/l (0,025 - 0,064 mg/l).

Potassium occurs in large amounts in the earth crust, while in seawater and in living organisms exclusively in the form of potassium compounds. With an average molar concentration of 1,02.10^-2 mol/l (expressed in mass units: 399 mg/l) potassium is the eighth most abundant element in seawater.

Nitrogen primary form on Earth is molecular nitrogen. With an average molar concentration of 2,25.10^-5 mol/l is nitrogen the fifteenth most common element in sea water. Expressed in mass units, the nitrogen concentration ranges between 0 and 45.10^-6 g/l (0 - 45 μg/l).

Due to its high reactivity, phosphorus occurs in nature only in the form of phosphorus compounds, to the greater extent in the minerals of Earth crust. According to its average molar concentration of 1,6.10^-6 mol/l, phosphorus is the sixteenth most abundant element in seawater. Expressed in mass units its average concentration is 4,96.10^-5 g/l (50 μg/l).

Amino acids (AA) are in general any organic compounds containing carboxylic (-C00H) and amine (-NH2) functional groups. From among vast number of AAs, most important are L-alpha-amino acids - headstones of all proteins and thus key in natural sciences.

Fatty acids (FAs) are organic monocarboxylic acids. Their molecule always begins with a methyl group (-CH₃) and is terminated with a carboxylic one (-COOH). In-between there are at least 6 methylene groups (-CH₂-) and may contain one or more double bonds (-CH=CH-). Carboxylic acids with a lower carbon atom number than 8 are not considered as fatty acids.