The sea is a huge collection of water collected on Earth. The sea separates land from one another, and one continent with another. (Also read: 8 Processes of Continents and Ocean Formation). Most of the sea on this Earth looks blue.
The color of seawater depends on water molecules in absorbing and reflecting sunlight, water substances dissolved in the seawater, types of deposits, and organisms that live in the ocean floor. The cause of white sea water is because there are glacial deposits on the sea floor. Usually found in the polar region.
The color of water is caused by the presence of decayed particles of organic matter, natural metal ions (iron and manganese), plankton, humus, industrial waste, and water plants.
The presence of iron oxide causes water to turn reddish, while manganese oxide causes water to turn brownish or blackish. Iron content of 0.3 mg/l and manganese levels of 0.05 mg/l are sufficient to cause coloration in waters (Peavy et al., 1985 in Effendi, 2003).
Calcium carbonate originating from calcareous regions creates a greenish color in the waters. Organic materials, such as tannins, lignin, and humus acid from the decomposition of dead plants give rise to a brownish color. You can make growth and development in plants as additional information.
The water color cultivation environment that is found also varies and is influenced by the content of plankton that is contained in water, phytoplankton and zooplankton, suspended solutions, decomposition of organic matter, minerals, and other materials dissolved in water. (Also read: 15 Main Elements in Ocean Water).
Water color caused by the dominance of plankton can affect the color of water, so that indirectly from the color of the waters, we can also describe the fertility of the water. The color of water caused by the dominance of plankton includes:
Green sea water is caused by the presence of phytoplankton which emits its chlorophyll content to carry out photosynthesis. When exposed to sunlight, chlorophyll in phytoplankton absorbs most of the red and blue colors, and reflects green. Green sea water is usually seen in waters near the coast.
The blue sea is the color of the sea that we see most often. The blue color is basically the color of the long wave of ultraviolet light, so it is not surprising that almost all the sea in the world is blue. The sun’s most blue rays are reflected more than other rays.
The sea is yellow due to the large amount of mud deposits on the seabed. The mud is the result of metabolism from various materials on land that produce yellowish brown soil, which is carried by the flow of water until it reaches the ground. Examples of these waters are the yellow sea in the waters between Japan and China.
- Dark Green
Dark green sea is caused by the dominance of Mycrocystis, Spirulina, Oscillatoria, and Phormidium which are included as blue green algae. This plankton indicates the amount of organic material in waters such as ammonia and hydrogen sulfide, so that waters with this color are not good for aquatic biota cultivation.
- Brownish Yellow
It is caused by Chaetocheros, Nitzchia, Gyrossigma, and Skletonema including Diatoms. Diatoms will grow fast in low-temperature environments.
- Brownish Green
Due to the Bacillariophyta content, the color of this water is good for the aquaculture area because it indicates the number of phytoplankton that can be used directly by zooplankton. In the black waters, there are many black soil deposits. For example the Black Sea which is between Saudi Arabia and Egypt. (Also read: 10 Deepest Seas in the World and the Secret behind Them).
The sea is purple because of the presence of small organisms that emit phosphorous rays. The example is the Ambon Sea.
- Reddish Brown
Due to the fact that Peridinium and Schizothrix calcicolla or from the Phytoflagellata species are dangerous because they are toxic, some plankton can release endotoxin which is detrimental to aquaculture biota.
Hopefully the explanation above can answer your question why the color of sea water is different, like greenish and bluish color.