Science of Coastal Waters

The marine environment is, to a great extent, defined by the physical and chemical characteristics of ocean water. These characteristics and the limits to which they extend are very important in determining what kinds of organisms can live in a region. Both chemical and physical factors, which include salinity, levels of dissolved gases, density, and temperature, are more extreme in shallow waters than in other parts of the ocean. 

Anyone who has tasted seawater knows that it is salty. Although salinity is fairly constant throughout most of the ocean, it is exceptionally variable near the shore. Salinity refers to the amount of dissolved minerals, or salts, in water. The average salinity of ocean water is 35 parts per thousand, abbreviated as 35%o (per ml). (The symbol %o is similar to percent but refers to parts per thousand instead of parts per hundred.) 

Salts in ocean water come from dissolved solids that originate on the land. The action of weathering slowly dissolves rocks and minerals, which are carried to the ocean by water in streams, creeks, and rivers. A small percentage of ocean minerals also come from the atmosphere and from the Earth s interior. 

Most of the minerals dissolved in water form sodium ions and chloride ions. Ions are charged particles created when minerals break down and dissolve in water. Some of the other ions that find their way to the ocean are those of sulfate, magnesium, calcium, and potassium. 

The salinity of water can be affected by a lot of factors. Anything that removes water from the ocean causes the salinity to increase. When water evaporates or freezes, it is 

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