Salinity
Definition of Salinity
Salinity is the measure of the concentration of dissolved salts in water, usually expressed in parts per thousand (ppt). Salinity influences water density, buoyancy, and the types of organisms that can live in different aquatic environments, with oceans having higher salinity than freshwater bodies.
How Salty Water Is
Salinity is a measure of how much salt is in water. Ocean water has a lot of salt, while freshwater in lakes and rivers has very little. Scientists measure salinity to understand how salty different bodies of water are and how it affects the plants and animals that live there.
How Salinity Works
Salinity is usually measured in parts per thousand (ppt). For example, ocean water has a salinity of about 35 ppt, meaning for every 1,000 parts of water, there are 35 parts of salt. Salinity can change in different places. Near river mouths or melting ice, ocean water is less salty. In hot areas where water evaporates, like the Red Sea, it’s saltier.
Why Salinity Is Important
Salinity affects what kinds of animals and plants can live in the water. Some creatures, like dolphins and sea turtles, need salty water to survive. Others, like frogs and freshwater fish, can only live in water with low salinity. It also affects how water mixes and moves in oceans, which impacts global currents and climate.
Examples of Salinity in Different Waters
- Oceans: High salinity, around 35 ppt.
- Lakes and Rivers: Low salinity, usually less than 1 ppt.
- Saltwater Lakes: Places like the Dead Sea are super salty, with salinity as high as 300 ppt!
Importance to Humans
Salinity matters for humans, too! We can’t drink salty ocean water, so freshwater with low salinity is crucial for drinking, farming, and industry. Desalination, a process that removes salt from seawater, is used in some places to create drinking water.