Why is Caribbean water so clear? This question is sure to pop up if you have already witnessed the darker water of the Atlantic Ocean.
It is true that the Atlantic Ocean’s darker water color is more surprising than the clear blue water of the Caribbean.
Still, you may want to know the science behind that water being so clear. So, why is the Caribbean water so blue and clear?
The Caribbean water is so blue and clear because of the lack of plankton, which means there is no chlorophyll to darken the color.
Witness the Beauty of the Caribbean Sea
The term “the Caribbean” refers to the geographical region that includes the islands and coasts of the countries that surround the Caribbean Sea.
Positioned between South America and the Gulf of Mexico, this body of water is found to the southeast.
Interestingly, the Caribbean Sea is technically a part of the Atlantic Ocean – Island chains divide the Caribbean Sea from the Atlantic Ocean.
The Atlantic Ocean and this body of water visually diverge at their meeting point, despite the fact that they are both oceans.
Fact: The Caribbean is much smaller than the Arctic Ocean but is still home to over 14% of the world's reefs.
The Mesmerizing Color of Caribbean Water
Compared to the deep “marine blue” of the Atlantic Ocean, the Caribbean Sea has a more subtle turquoise.
The color of the water at the surface is somewhere between blue-green and green. The Caribbean has similar depths and deep-water temperatures to the Atlantic in its broader basins.
It is widely believed that deep water from the Atlantic flows into the Caribbean and helps to deepen its sea.
Fact: You can find over 7,000 islands belonging to 28 nations in the Caribbean Sea.
Why is Caribbean Water So Clear?
People may consider why Caribbean water is so clear if they are used to the murkier waters of an ocean.
The Caribbean region is geology ancient and when classified its waters are considered an oceanic sea.
It is mainly because all that separates them from the Atlantic Ocean are strings of volcanic islands and not one solid land mass.
To humans, the Caribbean beaches are a holiday paradise, but this is far from the case for the creatures living in the water.
The reason is that it has an almost sterile environment for sea life to thrive, which is another reason why it looks so clear.
The Story Behind the Clear Water of the Caribbean
The Caribbean’s water is so clear and turquoise because it lacks life, at least in significant numbers.
The Caribbean Sea is shallow and lies under a harsh tropical sun.
The water is constantly heated to noticeable warm, 27°C (80°F) on average and it varies as little as 3°C (37°F) throughout the year.
Over millenniums this has created a warm marine environment. As an ecosystem, it is not as conducive to life as those of colder seas and oceans, like the fertile Atlantic.
An Almost Sterile Environment
For most sea life, large and very small, the Caribbean sea can best be likened to a desert.
There are enormous expanses of featureless plains that are almost devoid of life under its waters.
One essential, the microscopic plankton that is the producer at the base of the oceanic food chain, find it near impossible to survive and flourish in the region.
The Role of Plankton and Phytoplankton in Water Color
Most phytoplankton and plankton are single-celled microorganisms living and dying on the water’s surface.
Eggs and larvae of larger creatures are also present in this soupy stew of protozoans, diatoms, and tiny crustaceans.
They work together to sequester carbon dioxide, convert sunlight into sugars, and expel oxygen.
Over 95% of marine food webs rely on phytoplankton. And because of their presence, the color of the water can become darker.
The Absence of Plankton in the Caribbean
It is this lack of plankton that leaves the waters of the Caribbean so clear.
Its absence as a primary food source has forced the few creatures that do live there to evolve other ways to gather their energy as food.
Corals, for example, prefer clear, warm water and have evolved a relationship with the algae around them that is mutually beneficial.
The seawater may be near sterile, but there is enough sunlight for the symbiotic algae to provide most of the food for the pair using a process called photosynthesis.
Fact: As per geological estimates, it is thought that the Caribbean Sea is somewhere between 160 and 180 million years old.
The Color of the Caribbean and the Role of Chlorophyll
Chlorophyll is a molecule produced by plants, algae and cyanobacteria. In green plants, it helps convert light energy into chemical molecules.
All green plants, including plankton, make their food by using this pigment. They use it to convert the energy in sunlight into carbohydrates and sugars they can use. But, chlorophyll also has an impact on how you see the watercolor.
Chlorophyll in the Ocean
In the ocean, chlorophyll is the most important light-absorbing substance, just as it is in green plants on land.
High concentrations of chlorophyll-rich plankton can turn bodies of water from clear blue to all shades of green. The exact shade depends on the kind of plankton it is and its numbers.
Because food webs in every type of ecosystem begin with photosynthesis, including those in the sea, all life on Earth is only possible because of chlorophyll.
As well as relying on the oxygen, produced in cell respiration, all the other organisms in the food chain rely on the sugary carbohydrates plants for their energy to sustain life.
What Does A Clear Blue Sea Suggest?
The basic principle scientists have adopted when assessing the color of an ocean from space is based on chlorophyll.
It means the more chlorophyll-producing phytoplankton in the water, the greener it will be.
Without plankton, the Caribbean water is low in oxygen and nutrient poor. Even dead matter, such as it is, cannot be recycled in the usual way.
With water that is so warm and so shallow, there is no cold-water layer to pull the detritus down to where it can decay.
So, when asking why is the Caribbean water so blue and so clear, the reason is mainly because there are no plankton with their chlorophyll in it to color it.
However, there are other factors at play.
Fact: It is estimated that the Caribbean Sea provides over 170 million tons of oil annually, making it one of the world's major oil-producing locations.
Why is the Water Turquoise in the Caribbean?
Without plankton and phytoplankton, the Caribbean water appears all shades of blue, particularly the turquoise the sea is renowned for.
This has to do with how sunlight behaves when it hits the water, along with how deep the water is at any point.
As a rule, the deeper the ocean, the deeper the shade of blue.
At its deeper points, not as much sunlight reaches the bottom. The deep water absorbs almost all the sun’s rays, creating a darker shade.
The Shallowness of Water
This means that the shallower the water, the lighter the blue it will be.
However, there is one more factor that helps create the unique turquoise of the Caribbean. This is the material that makes up the beaches and the sea bottom.
Light-colored sand, made up of eroded fragments of dead coral, reflects back even more of light.
Although sunlight appears white to the eye, it is light that is made up of a spectrum of colors.
As the light beam hits the water droplets in the sea, the beam is split and broken down into its constituent colors. A rainbow works in the same way.
What Happens to the Sunlight?
Three things can happen when sunlight hits seawater.
The light can be:
- Absorbed – heating the shallow water.
- Scattered – bouncing off the water’s surface in many different directions.
- Reflected – bounced off the water’s surface in the direction it came from.
In the Caribbean, where the water is shallow, most sunlight is reflected back.
There are only a few other substances, usually based on organic carbon, dissolved in water that can also absorb light.
Keeping the Reflection in Perspective
Whereas most of the wavelengths that make up the color spectrum are absorbed by water, the blue wavelengths are not.
Instead, these blue wavelengths are reflected back in the direction they came from, the sky.
This is the main reason oceans everywhere are considered to be primarily blue.
Why is Caribbean water so clear? It is mainly because the sea is devoid of phytoplankton and plankton, their green chlorophyll.
These organisms also produce the natural sediments and particles as they die to add to the sea snow, making seas darker.
This is not the case with the Caribbean, which is why you find it to be clear and blue.