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Dotting the coastlines of several of the MHI are anchialine pools, formed when freshwater percolates through the ground and meets up with salty water that enters through subterranean cracks and fissures in lava or limestone. The result is a landlocked body of water with secret passages to the sea. The water is stratified, layered with salty, denser water at deeper levels, and brackish to fresh water near the surface. Salinity levels in these pools are also influenced by tidal changes and solar intensity. While this habitat would seem a rather challenging place to live, a surprising diversity of creatures call it home, including the poster child for Hawaii's anchilaine pools: Halocaridina rubra. The 'opae 'ula, a.k.a Hawaiian red shrimp, or volcano shrimp, is a little thing, just up to a half inch in length. These are the shrimp that you may see for sale in air-tight "ecospheres", and while their trade has brought attention to this otherwise little-known decapod, their fates are literally sealed.
In their natural environment they feed on algal and bacterial mats within the pool, scraping and filtering these with hair-like structures on their chelipeds. Detritus and plankton may also be consumed. 'Opae 'ula were used by early Hawaiians in their fish ponds as food for larger fish, such as 'opelu, and they are also a favorite food of seahorses. They are unusually long-lived, with estimates from 10-15 years in he wild, and reproduce underground. Hawaii is thought to have approximately 650 anchialine pools, with the vast majority of them found on the island of Hawai’i. Much remains to be learned about these pools and the creatures that live there. In the meantime, it is important to respect these unusual habitats, leaving them undisturbed and free from alien species, such as guppies, tilapia and mosquito fish.
welcomes you to visit with the all the wonderful flora and fauna that we share this lovely aina with.