The Many Shades of Water: A Sea of Green for St. Patrick’s Day

Source: The TeraMar Project - March 17, 2017 in Featured, TMP

The Many Shades of Water: A Sea of Green for St. Patrick’s Day
Photo: Bart Heird/Flickr (CC BY-NC-ND 2.0)

For more than 50 years now, the Chicago River has turned green on St. Patrick’s Day. This is no work of a magical leprechaun, just a couple of motorboats and about 40 pounds of a powdered vegetable die.

Water is an incredible substance that has the ability to transform into spectacular colors, under the right conditions. Most water on Earth is made up of different cocktails of organic materials, chemicals, and aquatic life. And sometimes when the right ingredient is added to the recipe, the result can be an incredible change in color. In the case of Chicago’s St. Patrick’s Day Parade, the powder used was originally designed to turn a bright green when it comes in contact with human sewage. I might think twice about going for a swim after learning that.

Green isn’t the only color that water can turn into. Water can glow, turn pink, become earthy red, and even a majestic turquoise blue. And this can happen both naturally and unnaturally.

But let’s start with the basics: the colors of the ocean. Ocean water for the most part comes in 2 shades: clear and a darker blue/green. In the tropics, water is clear because it lacks suspended particles and plankton, which allows light to penetrate deeper under the surface. As you move further from the equator into colder waters, a greater concentration of phytoplankton and nutrients mix with the seawater, resulting in a darker blue and green appearance. You could ask St. Patrick himself, as the waters off the coast of Ireland boast this dark blue and green hue.

What about all this talk of seas that can glow? Well, in some tropical waters around the world a species of phytoplankton can light up in the water, but it needs the right conditions to grow. These plants (dinoflagellates) can only exist in areas where freshwater from a river meets the tropical sea, and finally combines with nutrients from red mangrove trees. Under these conditions, the bioluminescent plants can become abundant in the water, and every time the current disturbs them they give off a sparking glow. The sea becomes alive with their presence.

Bioluminescent Bay

Photo: Kris Williams/Flickr (CC BY-NC-ND 2.0)

And pink? How can water turn pink? Pink colored lakes such as Australia’s Lake Hillier are a natural marvel. They get their striking color thanks to the presence of salt-loving algae that produce carotenoids. Once the lake water reaches a salinity level greater than that of sea water, and the temperature is high enough with adequate light conditions, the algae begin to accumulate their red pigment (beta carotene6). Similarly in Siberia, Lake Burlinskoye turns pink every August when the conditions become salty enough. Here, an overload of microorganisms called Artemia Salina (a pink brine shrimp) is the cause. This lake has been changing color earlier than usual in recent years most likely due to climate change. The lake is the largest deposit of Salt in Western Siberia and was apparently a favorite of the Russian royal family.

Canada’s Dusty Rose Lake in British Colombia is pink for a different reason. Here it’s due to the particulates in the glacial-melt waters nourishing it. The surrounding rock is purple and pink in color and the water feeding the lake is actually said to have a lavender hue.

Lake Hillier

Photo: Aussie Oc/Wikimedia Commons (CC BY-SA 4.0)

Now to the color red. Have you ever heard of a ‘red-tide’? Scientists prefer to call these Harmful Algal Blooms, and they can occur all over the world’s coastal seas when specific species of algae grow rapidly and out of control. Not all species of algae are harmful, but these ones release a toxin that can kill fish and make shellfish dangerous to eat. They get the name ‘red-tide’ from the red color of their bloom in the water.

Another darker shade of red can happen in freshwater. Extraordinarily, a couple were visiting Cameron creek in Alberta, Canada, when they witnessed a jaw dropping moment where the usual colours of the clear waterfall transformed into ‘tomato soup red’. This was caused by a vicious storm whereby the high levels of rain stripped a red colored sediment called argolite from the rocks and into the water.

And finally, where can one see the mesmerizing turquoise-blue color? In Costa Rica, there’s a river called Rio Celeste that uses volcanic minerals (alumino-silicates) to change colors. Two rivers meet upstream at a junction, where one river is carrying the volcanic mineral. When the rivers mix, the reaction results in an immediate change in color that is incredible to witness. Locals say that the color is as blue as the sky, a blue with a ‘celestial’ hue.

Rio Celeste

Rio Celeste: the junction where 2 rivers meet.

Rio Celeste

Rio Celeste: The Waterfall

So, whether it’s a St. Patrick’s Day green, or a flamingo pink, the waters of the world can become a jaw-dropping sight under the right conditions. It all boils down to what’s in and around the water that alters its hue and adds to the many kaleidoscopic and defining colors of water we see in the world today.


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