The principal component of sea water is obviously water (H2O), but above and beyond that, sea water is a complex mixture of materials dissolved from the earth's crust and released by organisms. Dissolved gases, such as oxygen (O2) and carbon dioxide (CO2), nutrients, temperature, and pH all significantly influence the marine environment.
Salinity
The salinity of sea water -- typically 3.5 percent -- is caused by dissolved salts. Sodium (Na), at a typical concentration of over 10,000 parts per million, is the major contributor to salinity. Salinity is important because it affects the transport of water into the cells of marine organisms.
Dissolved Gases
The concentration of dissolved oxygen in sea water is important because the oxygen is extracted by fish and other animals with gills for respiration. Similarly, dissolved carbon dioxide is used by marine plants for the process of converting inorganic matter into organic matter, known as photosynthesis.
Nutrients
Nutrients like nitrogen (N), phosphorous (P) and potassium (K) -- derived from animal feces and the decomposition of organic material -- are important for the growth of marine plants. Iron (Fe) is also an important component for the growth of microscopic free-floating plants, known as phytoplankton.
Tags: carbon dioxide, important because, marine plants, organisms Dissolved
