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How did early Hawaiians survive and prosper in the hot and parched lava
fields of west and south Hawaii Island?
One key resource many people depended upon
were small pools of brackish water scattered in lava fields near the coast.
Early Hawaiians used the water in these special pools for
bathing, drinking,
and watering their crops.
They altered many pools to create
fishponds such as the famous ones at Puuhonua o Honaunau.
Later named anchialine pools, these water sources were essential to many of the
settlements along the populated coastlines of leeward Hawaii Island.
This is how it works.
Groundwater percolates down from the rain-fed mountains as water from the ocean
moves through cracks in the porous lava.
The fresh and salty waters
meet in shallow coastal pools.
The tides and other factors influence the salt content of these pools
which create a special habitat for unique organisms.
If you look closely you will see a tiny world of native shrimp
called opae ula,
snails, and insects.
Modern coastal development has led to the destruction of countless of these special
pools in Hawaii.
Other threats include the introduction of invasive species like mosquito fish and tilapia.
And upslope
pollution entering the groundwater system.
If too much freshwater is removed from the natural system for watering lawns
or other human needs,
the pools will become saltier as a result.
Due to the global uniqueness and frailty of anchialine pools,
the National Park Service Pacific Island Network regularly monitors the water quality
and animals inhabiting the pools in the national parks on the island of Hawaii.
(Biologist) This one is 12.2 millimeters.
(Biologist) Due to the vulnerability of these pools to alien species, freshwater withdrawal,
and pollution
they tend to be very good indicators of the health of the entire ecosystem.
If we find excess algae in the pool or the native species are missing,
then we have an idea that something's wrong.
On the other hand if we finds pools with lots of opae ula, the native shrimp,
then we have a pretty good idea that all is well in the water system.
Anchialine pools are a life-line for many of the plants and animals along Hawaii's dry
and rugged coastlines.
A healthy pool is a good sign of the health of the coast itself.