That means that they maintain a constant ratio with respect to each other. If you know the concentration of one of these ions in seawater, you can automatically calculate the concentrations of the others based on these ratios. Salinity can be calculated from the electrical conductivity of water or from the concentration of chlorine. Karl Dittmars, aboard the HMS Challenger, was the first to measure ocean salinity. Some elements and compounds in seawater pass rapidly through the dissolved phase and are not conservative.
Examples are nutrients, organic matter, and dissolved gases.
C. Residence time for solid materials dissolved in seawater 1. All dissolved materials in sea water pass through cycles. The amount of time a material spends dissolved in ocean water is called its residence time. The salinity of the oceans represents a balance between all the individual cycles and has been relatively constants for the last billion years or so. The composition of these gases near the ocean's surface is in equilibrium with the atmospheric composition.