Why do seawater have different colors?

Seawater has many different colors depending on the physical and biological characteristics taking place there.

Explanation of different colors of seawater

Sea and ocean colors change markedly over time and place, from turquoise, green to blue, navy blue, gray and brown. This change is caused by the process of physical and biological changes.

Different colors of seawater, off the Tasmanian coast.(Photo: NASA)

Human eyes contain cells capable of detecting electromagnetic radiation at wavelengths from 380 to 700 nanometers. Each wavelength corresponds to a different color, similar to when we observe a rainbow.

Water molecules absorb sunlight better in long wavelengths like red, orange, yellow and green. Meanwhile, blue has a shorter wavelength so it is less absorbed by water. So it penetrates deeper, making deep waters look greener.

In addition, short-wavelength light is more likely to be scattered or reflected in different directions from the sea to the observer's eye, making the ocean often blue.

Sand and mud originating from rivers flow into the sea, or from the seabed also affect the color of the water. When the purity of seawater changes, the particles suspended in the water increase the scattering of light , making the sea water become green, yellow or brown.

Phytoplankton are also an important biological cause of seawater color. They are single-celled algae that use chlorophyll to absorb sunlight, turning water and carbon dioxide into organic compounds that make up the body. Through this process, unicellular algae are responsible for producing about half of the oxygen that we breathe today.

" It is useful to be able to distinguish different phytoplankton types, because each of them has different functions in the ecosystem, " Venetia Stuart, scientific coordinator organizing International Ocean Color. , member of the Earth Observation Committee (CEOS) said. " Carbon rings help determine CO2 concentrations in the future, so that information can be used in determining future climate change patterns."

Phytoplankton absorb electromagnetic radiation in the red and blue spectrum , and reflect green light. This is the reason why in the waters they thrive, the water looks more green.