Tidepools

Tide pools become completely isolated environments during low tide.

NPS Photo / Manuela Cortes

For visitors who appreciate the finer details, the tide pools at Kaloko-Honokōhau National Historical Park offer a unique glimpse into a miniature version of a reef. Tide pools are unique coastal ecosystems found in rocky intertidal zones where the ocean meets the land. They are created when seawater fills depressions in the lava rocks during high tide, and the water remains there as the tide recedes. During low tide, these pools become completely isolated from the ocean and create miniature habitats that host a rich array of marine life. For several hours, water in these pools will be heating up and evaporating, making them significantly warmer and saltier than the ocean. There is a surprising variety of organisms that have learned to adapt to this fluctuating environment and are able to survive the rapid and intense environmental changes that tide pools experience every day.

Tide pools support diverse food webs of marine organisms. The foundation of these food webs begins with limu, or algae, that convert sunlight into energy through photosynthesis. Most of the limu in the pools is green and brown turf algae. For those with a sharp eye, the tide pools offer the chance to discover a variety of other limu species beyond the common turf algae. Observing these algae up close reveals their fascinating adaptations to the intertidal environment, such as their ability to withstand periods of dryness.

 

This species of Cladophora has evolved stiff filaments to keep water inside.

NPS Photo / Manuela Cortes

The energy produced by limu is taken up by several herbivorous species, including invertebrates like snails and sea urchins. The most common species to observe are black Nerites (pipipi), small snails with ovate, dark shells and are endemic to Hawai‘i. These snails can seal themselves tightly against the rocks to retain moisture during low tides. After they die, their shells remain in the tide pools and are often used by small hermit crabs seeking protection. Small clams and sea urchins can also be seen hiding in cracks and crevices of the tide pools.

 

Small pipipi attached to a wall of algae.

NPS Photo / Manuela Cortes

Tide pools also provide refuge for many species of fish. Small fish can be protected from large predators that are unable to survive the shallow environment. Juvenile convict tangs (manini), less than 5 centimeters in length, are commonly found in tide pools, grazing on patches of turf. As adults, these fish are important herbivores in coral reefs. Several species of tide pool gobies (‘o‘opu‘ohune) and zebra blennies (pāo‘o) can be seen lying on the bottom of the tidepools, remaining completely still as they try to camouflage themselves. Juvenile Hawaiian flagtail fish (āholehole) and Hawaiian sergeant fish (mamo) can be seen schooling with members of the same species, while others like blackspot sergeant fish (kūpīpī) tend to remain solitary.

 

Hermit crab are commonly spotted in our tide pools

NPS Photo / Manuela Cortes

As you explore, please remember to tread lightly. The tide pools are fragile habitats, and it is essential to respect the marine life that calls them home. Avoid stepping on the delicate organisms, and refrain from disturbing or collecting any creatures. Rocks can be wet and slippery, and large waves may appear at any time, so exercise caution.