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Seawater Salt Levels: Factors and How to Measure

by Widiya

About 70% of the area on the surface of the Earth is covered by water, with a comparison of 5 oceans around 7 continents. In this article, we will discuss about the salt content contained in the sea, where the water is water that comes from the sea or ocean water. Seawater contains salts, dissolved gases, organic matter, and particles that are not dissolved. Why is seawater salty? Is it really because it contains a lot of salt? The salt comes from the weathering process of rocks found on land so that it dissolves and flows with river water or swamp water, which then empties into the open ocean.

(Also read: 10 Ways to Preserve the Sea and the Beach for the Earth)

Factors Affecting Sea Water Salt Levels

The salt content in each ocean differs, depends on the following points.


The more frequent evaporation, the more salty water will be. Remember that even fresh water contains organic mineral compounds, one of which is salts. If water evaporates, then deposits occur on the seabed. The more salt settles, the more salty water is.

Freshwater Import

The more fresh water that enters, the more the salt content drops. In the open ocean, fresh water comes from rainwater. In coastal areas, fresh water comes from rivers and swamps. While at the poles, fresh water comes from melting ice.

Mixing Water

The mixing of surface water and water from the inside with different levels of salt can reduce the salt content of seawater.

(Also read: 13 Effects of Ocean Acidification on Aquatic Organisms)

How to Measure Salt Levels in Sea Water

Measuring the salinity of seawater is done to study the characteristics of the sea. The five oceans in the world, namely the Pacific Ocean, the Arctic Ocean, the Atlantic Ocean, the Indian Ocean, and the Antarctic Ocean have their own characteristics.

The term used to measure the ocean salinity is halinity, which is based on halides, especially chlorides. In oceanography, the salinity unit is not in percent (%), but “thousandth part” or “part per thousand” abbreviated as ppt, or commonly called per-mille (‰). There are several types of salinity measuring devices.

  1. Refractometer

Refractometer is a salinity measuring instrument which is commonly used and can be used by everyone. The principle of this tool is to use a light refraction index to determine the level of water salinity. Because it requires direct light to get the refractive index, the measurement should be done outside the room that gets sunlight. Measurements in a closed space with light from a lamp make the results obtained are less accurate.

(Also read: 3 Differences between Sea Wave and Ocean Flow)

The way to measure the ocean salinity using a refractometer is as follows:

  • Open the refractometer cover, the glass prism cover, then wipe the surface using distilled water and a cloth with clean tissue.
  • Drop the sample water to be tested on the prism glass, then point the refractometer toward direct light.
  • On the shooting screen, blue and white fields will appear. The boundary between the two is the level of salinity of the water.
  1. Salinometer

The working principle of the tool is based on the electrical conductivity that can be produced by the liquid being tested. If the power is large, the salinity is high, and vice versa. And this tool is only used in testing laboratories.

The method of measuring using a salinometer is as follows:

  • Take a measuring cup or test tube and pour the water sample to be tested. Dip the salinometer into it.
  • Salinity will be read in scale.
  1. Digital Measuring Instrument (Salinity meter) and Data Logger

It is a digital measuring instrument which is practical and accurate, usually used to observe very small changes in the salinity of the water being tested. Portable Salinity meter can be carried anywhere and the usage is very easy, just dip it into the sample water then turn on the measuring instrument by pressing the button. The LCD screen will show how much the salt content is.

(Also read: 10 Marine Natural Resources and Their Benefits For Us)

Salt Conditions in World Sea Water and Its Impact

The level of salt in the world’s seawater averages 3.5%. The fewest or freshest salt seas are in the eastern Gulf of Finland and in the north of the Gulf of Bothnia, both of which are part of the Baltic Sea. While the sea with the highest or salty salt content is the Red Sea, at 40%.

However, if you have ever heard the term Dead Sea or Salty Sea, even though it is called the sea, actually the Dead Sea is a salty lake with the lowest land in the entire surface of the Earth. For this reason, the Dead Sea water cannot flow outside; therefore, seven million tons of water in the Dead Sea evaporate every day and this cause the water there even more salty. The level of salt in the Dead Sea is 30%, which means nine times saltier than ordinary sea water. However, because of the lower surface, in 2017 the Dead Sea is now connected with the Red Sea.

The benefits obtained from high salt levels, such as those that occur in the Dead Sea, are the many mineral and gas contents which are beneficial to humans. Among these minerals are magnesium, zinc, sodium, bromide, sulfur, potassium, and calcium. The benefits of these minerals are good for the skin, such as increase skin metabolism and permeability, provide a relaxing effect as a disinfectant, increase oxidation and electrical processes in the muscles (potassium), and clean the skin pores.

(Also read: 20 Importance of Marine Life Conservation)

In addition, if a filter and settling process is carried out, salt crystals will be produced which are useful for everyday human activities such as cooking. The measurement of sea water salinity can predict the density of fish in the sea. That is, at a certain level of salinity, fishermen can catch fish according to their location.

Even though the impact of salinity itself is the growth and proliferation of disturbed marine animals, if the salinity of seawater does not correspond to the salinity of the body’s cells, it will inhibit the growth process. In addition, sea water can have nutrients that can be used for soil and plants. However, if the salinity level is too high, this can cause soil dispersion. As a result, the aggregate of the soil breaks down, minerals that are small in size and organic particles actually clog the soil pores and result in reduced flow of water into the soil. Then this will lead to changes in soil porosity conditions and reduce water permeability.

Those are several levels of seawater salt. At least in a liter of sea water, approximately there are 30 grams of salt. So, can you imagine how salty the sea is?

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