A quick stroll through the Cabo Rojo National Wild Refuge in southwest Puerto Rico leads to an unexpected sight. It is cotton-candy pink water that glistens in the sun. Las Salinas is the pink salt flats. It covers 1,249 acres and consists of two natural lagoons 18 inches deep. This area has been altered to mine salt.

The color can range from bright pink to cloudy to dark brown depending on the day. However, it is more common to be pink. It is a mixture of algae, bacteria and salt.

Dunaliella salina, an algae, is responsible for the salt flats' water color. It's part of the green algae family but is full of carotenoids, which are pigments that give many orange and red fruits or vegetables their color. These carotenoids in this particular algae are red. Archaea is a bacteria and prokaryotic species (meaning that it is a single-cell organism without a nucleus). It also floats in salt flats. It also has a pigment called Rhodopsin, which is red.

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Lilliam Casillas Martinez is a biologist at University of Puerto Rico at Humacao and has coauthored many studies on microorganisms found in salt flats. The color of water depends on how much algae and bacteria it contains. Rainy seasons are when the salt levels drop [because the ponds have more water]. She says that if there is less salt, Dunaliella can survive and the ponds turn brownish-red. It gets very salty during dry seasons. The Dunaliella dies, and the bacteria and archaea take over. It becomes pink, pink and pink.

Some other hyper-salinated spots have a pinkish hue, such as the pink Lake Tyrrell, Australia, or the San Francisco Bay salt ponds. This is also the case for the Santa Pola saltern, which is more brown and red than the pink one. Cabo Rojo is home to a remarkable biodiversity and is easy to reach. It's also a great place to spend a day while on vacation.

The flats are used to mine salt regularly. In fact, Casillas Martinez claims that it is one of the oldest business in Puerto Rico. The flats were being mined by the Indigenous Araucos, Taino and Taino when Christopher Columbus arrived on the island in 1493. They had been doing so since around 700 C.E. The Spanish arrived and began exporting salt. They also enslaved Indigenous peoples to clean the salt. The Spanish refused to be accepted by the locals, who fought back for their control.

"There's a beach near the salterns, man-made pools that evaporate seawater," says Casillas Martnez. This is where the Spanish fought the locals for the salt flats. Walking distance from the beach is the salterns, which run right along the coast. You can also drive to the refuge via the beach.

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The U.S. took Las Salinas National Wildlife Refuge and Cabo Rojo National Conservation Reserve under their purview. Fish and Wildlife Service in 1974. However, a private company still extracts salt from the area using heavy equipment.

According to Casillas Martnez, the best time to visit salt flats is during the rainy season (April through November). Although the salty salterns appear reddish-brown due to their watery nature, wildlife (including large numbers of sea monkeys), thrives in this season. The surrounding plants are also newly green. The salt flats turn pinkest during the dry season (December to March). Visitors can see bright pink salt flats lined with dried salt crystals, as there is less rainfall to displace the organisms that cause the color. Around 40,000 birds migrate to the salterns each winter, including great blue herons and snowy plovers.

Cabo Rojo Salt Flats Interpretive Center serves as a starting point for guided tours. Reservations must be made in advance. Visitors can view a video on all the birds in the flats and read about the ecology and geology of the area. Then, they can climb the nearby observation tower. After that, they can hike through the flats along concrete dividers. It is forbidden to take salt, swim in the pools or climb onto salt mounds.

Casillas Martinez says, "You have mountains full of salt." It's hilarious because it looks like snow. It's not snow. It's also full of migratory bird species during the rainy season. It's amazing to be there during the afternoons. It's amazing to see all the birds singing and drinking, and it is beautiful."