How do oceanographers define salinity?

It's defined as the salt concentration in sea water. Ex: Sodium and Chlorure

Salinity is measured by the saltiness of seawater or the amount of dissolved matter in sea water.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.