- Saltwater biomes: These biomes are characterized by high levels of salt, typically in the form of sodium chloride (NaCl). Saltwater biomes include oceans, estuaries, and salt marshes.

- Freshwater biomes: These biomes are characterized by low levels of salt, typically less than 1 part per thousand (ppt). Freshwater biomes include lakes, rivers, streams, and wetlands.

2. By temperature:

- Coldwater biomes: These biomes are characterized by cold water temperatures, typically below 20 degrees Celsius (68 degrees Fahrenheit). Coldwater biomes include polar oceans, glaciers, and high-altitude lakes.

- Warmwater biomes: These biomes are characterized by warm water temperatures, typically above 20 degrees Celsius (68 degrees Fahrenheit). Warmwater biomes include tropical oceans, coral reefs, and shallow lakes.