Why did Kealia Wetlands turn Pink?

The current drought combined with excessive water diversions from the 3+ streams feeding into Kealia Pond has starved the wetlands of fresh water. The remaining water has turned hyper-saline. In addition to the recent die-off of all the fish, this has created these extreme conditions and resulted in a pink algal bloom for the first time. This is nature’s cry for help. Because we are taking too much water out of the landscape, and the natural systems are shutting down. 

Algae producing its own “Sunscreen”:
The drought conditions as so bad that the blue-green algae are producing beta-carotene (pink) as a sunscreen. Ask yourself how bad does it have to be for algae to have to put on sunscreen?
Extreme Drought Conditions:
Maui experienced an extreme drought in 2023. This reduced rainfall and the stream flow that normally feeds into the wetlands and ponds.  You can see in the above photo the larger part of the pond is dry and brown. This was the site of a huge fish die-off a few weeks before the photo was taken. The fish could not survive the increasing salinity and water loss. The remaining part of the pond still full of water is the nearshore estuary, which has a higher salt content. And has become hyper-saline, at about twice the salinity of the ocean.
About Keālia Pond:
The Keālia Pond lowland wetlands are a sediment basin, shaped like a shallow bowl sitting at the bottom of a 56-square-mile watershed. Keālia receives her water from both of Maui’s mountain ranges. Water comes from the Waikapū Stream in the West Maui Mountain and Kolaloa Gulch originating from Haleakalā, and several others.
Halophilic algae, “alga Dunaliella salina”
The extremely halophilic alga Dunaliella salina can also color saline waters pink. Although these algae are mainly responsible for the pink coloration of some saline lakes (e.g. Cane, 1962) and they are widespread in saline environments, halophilic bacteria are also usually present (Brock, 1979).
Why do Lakes Turn Pink?

Lakes turning pink is a fascinating phenomenon that has intrigued scientists and nature enthusiasts alike. The most common cause of pink lakes is the presence of salt-tolerant algae that produce carotenoids, such as Dunaliella salina, usually in conjunction with specific bacteria and archaea, which may vary from lake to lake (1). The orange/pink color of salt lakes across the world has often been attributed to the green alga Dunaliella salina, but other work has shown that bacteria or archaea are also involved 1. The most common archaeon is Halobacterium salinarum (1).

Pink lakes arise from a combination of factors, which include climate and hydrology of the continent beneath them, in particular the level of salinity (1). The orange/pink coloration of these lakes can be attributed to a variety of factors, including the presence of specific microorganisms, unique geological characteristics, or even the influence of human activities (2)Once the lake water reaches a higher salinity level than seawater and the temperature rises high enough, the reddish pigment beta-carotene begins to accumulate in the algae and turns the lake pink (3).


  1. https://en.wikipedia.org/wiki/Pink_lake
  2. https://www.ncesc.com/why-do-some-lakes-turn-pink/
  3. https://weather.com/science/nature/news/whats-turning-these-lakes-pink-photos