1. Freshwater:
- Salinity: Less than 0.5 parts per thousand (ppt)
- Sources: Freshwater is found in various sources, including rivers, lakes, ponds, reservoirs, and glaciers.
- Characteristics: It contains low levels of dissolved salts, minerals, and ions. These waterbodies support freshwater ecosystems with unique plant and animal species adapted to low-salinity environments.
2. Brackish Water:
- Salinity: Between 0.5 to 30 ppt
- Sources: Brackish water forms where freshwater meets saltwater, creating environments transitional between the two. It's common in estuaries, lagoons, deltas, and coastal wetlands.
- Characteristics: Brackish water possesses a mix of freshwater and saltwater species. The level of salinity varies greatly depending on the tides and freshwater inflow. It's not ideal for typical freshwater or saltwater organisms due to fluctuations in salinity levels.
3. Saltwater or Marine Water:
- Salinity: Generally more than 30 ppt
- Sources: Saltwater is primarily found in oceans and seas but can also exist in hypersaline coastal lagoons or salt lakes.
- Characteristics: It contains high concentrations of dissolved salts and minerals like sodium chloride (NaCl) and magnesium sulfate (MgSO4). Marine ecosystems have species specifically adapted to these higher salinity levels and thrive in the dynamic oceanic conditions.
The salinity levels determine the ability of organisms to survive and reproduce in these different water types. Each category supports its own distinct ecosystems and plays a crucial role in balancing and regulating the global water cycle.