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What body of water is red?

What body of water is red?

There are a few bodies of water around the world that appear red or reddish in color. This unusual phenomenon is typically caused by high concentrations of certain microorganisms, minerals, or chemical processes. Some of the more well-known red bodies of water include Lake Hillier in Australia, the Red Sea, and Grand Prismatic Spring in Yellowstone National Park.

Lake Hillier – Australia

One of the most famous reddish bodies of water in the world is Lake Hillier, located on Middle Island off the coast of Western Australia. This highly saline lake is about 600 meters long and covers an area of around 0.06 square kilometers. The striking color of Lake Hillier comes from a high concentration of Dunaliella salina – a type of algae that produces a red pigment. The algae thrive in the lake’s salty environment. The reddish hue of the lake stands out vividly against the blue of the ocean surrounding Middle Island. Lake Hillier’s unique color has made it a popular tourist destination in Western Australia.

When Was Lake Hillier Discovered?

Lake Hillier was first discovered and recorded by the explorer Matthew Flinders in 1802 while he was circumnavigating Australia. However, the indigenous Aboriginal people of Australia were likely aware of the lake’s existence for thousands of years before Flinders documented it. Flinders recorded in his journal that he had discovered a lake of a “rose colour” and theorized that the color could have come from algae that lived in the salt crust surrounding the lake.

What Causes Lake Hillier’s Red Color?

As Flinders speculated over 200 years ago, Lake Hillier’s distinctive color is due to algae that thrive in its hypersaline environment. The blooms of Dunaliella salina algae produce a red pigment that helps absorb sunlight in the lake’s salty waters. The pigment, known as beta-carotene, is the same compound that gives carrots and other vegetables their orange color. When the Dunaliella salina algae are highly concentrated in Lake Hillier during algal bloom events, their pigment turns the water a vivid reddish pink.

Other Theories About Lake Hillier’s Red Color

In addition to the Dunaliella salina algae theory, there have been some other hypotheses proposed about the cause of Lake Hillier’s color over the years:

  • High concentrations of halobacteria – Archaea microorganisms that thrive in salty environments and can produce red pigments.
  • Presence of red dye or pigment from nearby vegetation washing into the lake.
  • High concentrations of potassium and sodium oxides dissolved in the water.

However, extensive microbiological analysis of Lake Hillier has shown that Dunaliella salina algae are the definitive cause of the red color. The algae influence both the lake’s water and salt crust, creating a vibrant red landscape.

The Red Sea

The Red Sea, located between Africa and the Middle East, is another large saltwater body known for its reddish hue. It connects to the Indian Ocean in the south and is an important shipping route between Europe, Africa, and Asia. The sea was named for its color by ancient Greek, Latin, and Hebrew writers.

How Did The Red Sea Get Its Name?

The reddish color of the sea was noted by ancient historians and writers going back over 2,500 years. Some early theories for the color included that it was due to red-colored volcanic rocks or red sandstone along the shores. The ancient Greek historian Herodotus speculated that the color came from algae blooms, similar to Lake Hillier. The Roman historian Pliny the Elder also made note of the Red Sea’s color in his writings.

The sea’s color inspired its naming in Greek (Erythra Thalassa), Latin (Mare Rubrum), and Hebrew (Yam Suph). The English name Red Sea likely derives from the Greek phrase.

What Causes the Red Color?

It is now known that the Red Sea’s occasional reddish or orange coloration is caused by algal blooms, particularly of the algae species Trichodesmium erythraeum. This algae can rapidly reproduce in the Red Sea’s warm, nutrient-rich environment, creating dense blooms that color the surface waters red.

There are also high concentrations of metal oxides, including iron, in the Red Sea’s waters. When the iron oxidizes, it turns the water a rust red color. The metal oxides come from high amounts of dust, sediment, and minerals flowing into the sea from nearby deserts and rivers.

Grand Prismatic Spring, Yellowstone National Park

Yellowstone National Park in the United States is known for its stunning geothermal features including colorful hot springs. Grand Prismatic Spring is considered one of Yellowstone’s most beautiful hot springs, showcasing vivid bands of orange, yellow, green, and red caused by heat-loving microbial mats.

What Creates the Vibrant Colors?

The vivid rainbow of colors around Grand Prismatic Spring comes from heat-loving microbes known as thermophiles. The extremely hot water in the center of the spring allows red thermophiles to thrive. As the water cools further from the center, green thermophiles take over. The change in temperature and types of microorganisms creates concentric rings of color.

In addition to the microbial mats, minerals like iron oxide contribute reds and oranges, while silica provides a pale blue color. The combination creates a stunning multicolored pool.

Why is Grand Prismatic Spring Unusual?

At 370 feet in diameter, Grand Prismatic Spring is the third largest hot spring in Yellowstone and is considered the park’s most spectacular display of hot spring colors.

Most hot springs have a runoff channel on one side that distorts the colorful bands. But Grand Prismatic Spring is very circular and symmetrical, allowing the rainbow-like spectrum to radiate beautifully outward from deep blue center.

The enormous size, vibrant colors, and nearly perfect circular shape make Grand Prismatic Spring exceptionally photogenic and one of Yellowstone’s top attractions.

Other Notable Red Bodies of Water

In addition to the major reddish bodies of water discussed above, there are several other lakes and seas around the world that periodically appear red or orange due to algae blooms and mineral deposits:

  • Masazirgol Lake, Azerbaijan – Blooms of red-colored green algae
  • Lake Retba, Senegal – High concentrations of Dunaliella salina algae
  • Pangong Tso, India – Algae and sulphur deposits
  • Dallol Hydrothermal Field, Ethiopia – Salt minerals and hydrothermal activity
  • Hutt Lagoon, Australia – Dunaliella salina algae blooms


Unusual reddish bodies of water occur in diverse locations around the world, but the phenomenon is often caused by similar factors. Algal blooms, especially of halophilic microbes like Dunaliella salina, are a prime contributor. Other influences include high concentrations of red-hued minerals from local geology and hydrothermal activity. While the red coloration may appear unusual, it results from the wide array of microbial life that thrives in aquatic environments across the planet. The rare convergence of the right conditions allows these red waters to stand out vividly.

Location Type of Body Cause of Red Color
Lake Hillier, Australia Saline lake Dunaliella salina algae
Red Sea Sea Trichodesmium erythraeum algae, iron oxides
Grand Prismatic Spring, Yellowstone National Park Hot spring Heat-loving thermophilic microbes