A hydrologic cycle means a continuous movement or phase change of global water mass distributed in the hydrosphere, atmosphere and lithosphere. If the amount of seawater is increased, it influences to a change of sea water level that further affects on coastal areas and the organisms live in the areas. Nowadays, it’s clear that using lots of fossil fuels causes climate change leading to the global warming, the glaciers located on the poles are melted by increase of the average global temperature, and the sea level is elevated. The important physical properties of water are described as the follows:
Salinity is derived by dissolution of salts or other minerals in a body of seawater. The major salts are Sodium and Chlorine, while the minor are Magnesium, Sulfur, Calcium, and Potassium. The measuring unit of salinity is expressed as “part per thousand” (ppt). Generally, the average salinity of seawater is 35 ppt. and varied by seasons, precipitations, evaporation rate, location, and distance from rivers or coasts.
Temperature is a major factor controlling the distribution and abundance of marine organisms. Most marine organisms are cold-blood animals that cannot maintain their body’s temperature in the changing environments. Hence, water temperature is extremely important to their cells and metabolism and a small change of the temperature may significantly affect to marine life.
pH of sea water is about 8. The pH is lowered when carbon dioxide (CO2) is absorbed by seawater, whereas the pH is shift to higher value where the photosynthesis rate or using CO2 in water is high.
Density of sea water is negatively correlated to salinity and positively correlated to the temperature. The water mass with lower density tends to be drifted over the higher density causing a layer within water body called “Pycnocline”.