Issue 11.6: December 2008/January 2009

What Lies Beneath

story by Catharine Lo
photos by David Liittshwager

Just north of the notorious, heaving shore break at Sandy Beach, piles of strewn lava rock create a jagged coastline that buffers the raging surf. The waves wash gently into the spaces between the rocks, creating knee-deep pools where marine life thrives. It’s a drizzly New Year’s as I crouch at the edge of a tidepool with expert Chela Zabin. We sit still, watching for movement. I delight in the fact that the task requires no skill other than simply to be present. The rule of discovery at tidepools is: The longer you look, the more you’ll see.

I poke my finger into the water, rudely disrupting a hermit crab’s afternoon nap. Small camouflaged fish whiz by. Every few moments, a tiny black snail crawls another millimeter. I begin to see colors—colonies of green zoanthids and moldy tufts of red algae.

“Some of your little kid comes out when you turn a rock over,” Zabin says as she does just that and finds a cluster of pink tunicates. She puts the rock back in place and picks up a giant, white-spotted sea cucumber. Placing it upside down in her palm, she touches the underbelly. Sticky, gelatinous tendrils cling to her index finger. Those, apparently, are its feet. This particular brown echinoderm, Actinopyga mauritiana, or loli in Hawaiian, has an anus - through which it breathes—with five inward-pointing teeth to keep out the pearlfish that like to play house in its intestines.

“Some shoot their guts out,” Zabin says, describing the violent expulsion of the digestive tract (auto-evisceration, it’s called) that occurs when some sea cucumbers get stressed. Considering the ejaculatory behavior of this organism, it’s not surprising that many cultures regard it as an aphrodisiac. An expression used in Hawaiian love sorcery goes, He loli ka i‘a, ‘iloli ke aloha. “When loli is the offering, passionate is the love.”

Before I learned anything about them, I’d always found these sand-covered sausages to be absolutely repulsive. I still think they’re disgusting, but now I’m intrigued. They and the hundreds of other invertebrates, fishes and plants in these little pools along O‘ahu’s wind-battered Kaiwi coast are wholly foreign to me. They inhabit an intricate world along Hawai‘i’s coastlines called the intertidal zone—the area between low and high tide—a habitat that is largely overlooked in favor of the more glamorous coral reefs.

Intertidal habitats take multiple forms: tidepools, splash pools, limestone reef flats, rocky shoreline and lava rock basins. Hawai‘i’s most beautiful sites feature expansive pools that reflect the sky and tame the sea—places like Shark’s Cove on O‘ahu’s North Shore and Wai‘opae Pools on the Big Island. They’re especially inviting because you can reach them on foot; some pools are even deep enough for snorkeling.

The creatures that live in these liminal worlds are bizarre, “stranger than anything you’d find in Star Trek,” Zabin says. “They’re like aliens.” Take pi‘oe‘oe, for example, a barnacle that lives with its head attached to a rock and feeds with its feet. Or the tunicates—advanced, filter- feeding animals that like humans have a beating heart, but unlike humans, reverse their blood flow every fifty beats or so. The zoanthids that resemble fat, soggy Cheerios immediately succeed the loli as the most revolting creatures of the sea. A reddish zoanthid called limu-make produces a lethal poison that warriors in Hana, Maui, once smeared on their spear tips. Ironically, this poison, palytoxin, also possesses anti-carcinogenic properties.

We might not think of these bizarre bags of jelly as animals, but according to John Hoover, the author of Hawai‘i’s Fishes and the tidepool enthusiast’s bible, Hawai‘i’s Sea Creatures: A Guide to Hawai‘i’s Marine Invertebrates, more than 90 percent of intertidal organisms are invertebrates, not plants, and they’re as different from each other as they are from humans. They have adapted uniquely to their difficult habitat. They endure dramatic changes in salinity and temperature daily. They get scorched in the sun and pummeled by the waves. Whenever the tide rises, their predators move in.

Because of these extreme living conditions, intertidal animals—some of the most elaborately designed organisms on earth—take exotic forms and possess remarkable powers. The helmet urchin fuses its spines together to form protective plates when the water level drops. The Hawaiian pom-pom crab wields stinging anemones in its claws. The cartoonish bullethead rockskipper “runs” along tidepool bottoms using its fins like legs. At low tide it will jump safely from pool to pool.

By the end of my exploration of the pools along Sandy Beach, I come to agree with what the distinguished Bishop Museum zoologist Charles Edmondson wrote in his 1949 book Hawai‘i’s Seashore Treasures: “The seashore offers storehouses of treasures that may be opened to keen and observing eyes.” My New Year’s resolution is to keep mine open.


In Margaret Titcomb’s Native Use of Marine Invertebrates in Old Hawaii, there’s a black-and-white image of a Hawaiian woman in a long-sleeved mu‘umu‘u, waist-deep in water and holding a spiny urchin in her palm. In old Hawai‘i, shellfish and limu (seaweed) were gathered primarily by women and then redistributed by a chief’s officer. Until 1819, the kapu (taboo) system forbade women from eating coconuts, turtle, some fish and certain types of bananas. The variety in their diet, therefore, was enhanced by what edible treats they could scavenge at the shore.

Hilo native Eleanor Kalawai‘akamali‘iwahineli‘ili‘i Ahuna was the Martha Stewart of tide pool cuisine. Part field guide, part cookbook, her handwritten Hawaiian Shores … And Foods outlines traditional Hawaiian methods of harvesting and preparing shoreline seafood that she learned growing up by the beach at Keaukaha. She teaches tricks like catching ‘a‘ama (crab) with ‘opihi (limpet) meat and offers handy tips: The best season for harvesting ha‘uke‘uke (sea urchin) is when the fruit of the hala tree is ripe.

“One need not possess any elaborate kinds of equipment to harvest enough food for his family,” Ahuna wrote. “Fish, shellfish and seaweed, all rich in the vitamin and mineral resources we need in our daily diet, lie in abundance at our feet, in easy access at our beaches. … In Hawai‘i, one should never go without food, especially a ‘keiki o ka ‘aina,’ (child of the earth), for ‘ina a‘ole molowa ke kanaka, ola ke kino’ (if the person is not lazy, the body is healthy).”

Hawaiians also used marine invertebrates for tools and medicines. A porous sponge known as ‘ana could be crushed into a white powder to treat ‘ea (thrush). It was also used as sandpaper to polish canoes and wooden calabashes. The tentacles of the kauna‘oa (spaghetti worm)—it looks like Silly String—were dried and mixed with water as a remedy for cancer. The handsome shells of leho (cowries) made excellent scrapers and he‘e (octopus) lures.

Perhaps the most important bounty of the intertidal zone is limu, the edible seaweed that remains an important part of the Hawaiian diet; its salty tang is the ideal complement to poke (raw fish) and poi. Limu has numerous other uses. Take the versatile Sargassum echinocarpum, also known as limu kala: Found in rocky intertidal areas and reef flats, it can be eaten, used as bait or applied as a salve on coral cuts. Traditionally, Hawaiian priests used it in rituals to cleanse someone who had been watching over a dying relative, as well as to purify fishermen on the eve of ‘opelu (mackerel scad) season. It is also used in the tradition of ho‘oponopono, the healing of family conflicts. Kala means “to forgive.

These days, edible limu and shellfish are not as abundant as they once were. Easy access to tidepools makes them vulnerable to human impact, and many intertidal species are at risk of disappearing. Conservation is a priority at places like Wai‘opae on the Hilo side of the Big Island, which has a uniquely high diversity of species in a small area. Dr. Leon Hallacher, chair of the Natural Sciences Department at UH-Hilo, has studied the habitat extensively. “The biggest single danger is too many people. It’s so easy to inadvertently kick some branching coral and break it. People don’t know that they’re actually killing the polyps that they’re standing on,” he says. While Wai‘opae is a marine life conservation district, which restricts fishing and species collection from the area, other threats to the watery wonderland loom. Recent bacteria counts at Wai‘opae have been high due to overflow from neighboring cesspools. Invasive mangroves are choking out the coral. But much of the damage can be prevented, Hallacher says; it’s a matter of educating people.

Playing devil’s advocate, I ask Chela Zabin whether people would notice a difference if the intertidal creatures disappeared. I mean, do we really need them? “It might not change our lives,” she says, “but it would change the quality of our lives. A richness of experience would be lost. People seem to be universally fascinated by tidepools. It is sad to lose more pieces of our natural world, especially things that are uniquely Hawaiian.”

Chela Zabin’s foray into Hawai‘i’s intertidal zone began with a pestiferous barnacle. It was 1998, and the University of Hawai‘i zoology grad student had just read a journal article about Chthamalus proteus, a crustacean from the Caribbean that had recently found its way to Hawai‘i’s bays and harbors. The article maintained that it thrives because there is nothing in its habitat, the intertidal zone, to keep it out—no competitive exclusion, scientifically speaking. Zabin was skeptical. Could the inhabitants of Hawai‘i’s intertidal be so easily overcome? The invasive barnacle cohabitates with a native barnacle and appears benign so far, but it could be a “sleeper species,” meaning its introduction only seems benign until it adapts to its new habitat and takes off, becoming a major problem. Additionally Zabin found that a native limpet (Siphonaria) actually helps the barnacle settle, even though the limpets are harmed in the process.

In the course of her research, Zabin discovered a broader problem: While scientists have studied some of Hawai‘i’s intertidal organisms, nobody had really looked at the overall ecological system. Varying as little as a few tenths of a foot between tides, Hawai‘i’s intertidal is neither as dramatic nor expansive as other well-studied intertidal zones, like those in California, where the tide change can approach 10 feet.

In O‘ahu’s intertidal zone, Zabin found that 9 percent of the algae species are non-native, a high number compared with the percentage of invaders on the West Coast. She says virtually no research has been done to measure the effects of these invaders on intertidal communities, but given the way alien species have altered other seascapes, the impact could be significant. In fact, one such impact—the disappearance of edible algae at ‘Ewa Beach on O‘ahu—was a major impetus behind Zabin’s pioneering OPIHI project.

Six years ago, Zabin and UH associate professor of education Erin Baumgartner established the OPIHI project, a school-based intertidal monitoring program funded by the National Science Foundation which teaches K-12 students about marine ecology. The data the students collect—a survey of what species are found in various shoreline locations—serves as a valuable base line for this understudied ocean habitat. During a survey of thirteen sites around the Islands, Zabin and Baumgartner identified 322 species, about a third of which live exclusively in the intertidal zone. Over the five years since, with the assistance of graduate students Joanna Philippoff and Erin Cox and the observations of more than 500 K-12 students, the OPIHI project has collectively identified more than 600 intertidal species—the most complete inventory of Hawai‘i’s intertidal organisms to date.

The best time to go tidepooling, actually, is at night, when the marine life is most active. After a dinner party one night at an unnamed beach near Waimea Bay, a friend and I grabbed flashlights and scampered down the sand to a group of tidepools cut off from the sea by giant lava rock boulders. The spotlight revealed that what might be witching hour on land is rush hour in the water. In less than half an hour, in a space the size of an inflatable kiddie pool, I spotted two baby lobsters, a coral-banded shrimp and a moray eel—the kinds of creatures I thought were too elusive for landlubber eyes like mine.

I touched my first sea slug, a white-speckled sea hare known as Aplysia dactylomela, as it emerged to feed on algae. I saw baby kikakapu (butterfly fish) and manini (convict tangs) that were no bigger than a half-dollar. And I stood witness to the drama of life and death as a long, white tohei eel lurched forward and snagged a tiny menpachi (squirrel fish) between its jaws.

If you are interested in viewing these creatures for yourself, the best strategy is to visit at low tide, preferably after dark, and simply keep your eyes open. Walks along the South Kohala coast near Puako (Big Island), Kihei at Waipu‘ilani Beach (Maui) and the Makapu‘u shoreline (O‘ahu) bring you to shallow reef flats and sand-bottom pools vibrant with life. Step carefully; rocks can be slippery and sharp. Reef shoes and diving booties are recommended, while sandals and slippers are not. If you turn over rocks, put ’em back.

As tempting as it might be to stick your fingers in holes or under ledges, don’t do it. You never know where the dangerous puhi lau milo (undulated moray eel) or the ko‘e (fire worm) might be hiding. Avoid accidental encounters with the poisonous nohu ‘omakaha (scorpion fish) and wana (venomous urchin), whose spines can break off and remain beneath your skin. Even the harmless-looking pupu‘ala (cone snail) can deliver a malicious sting, so the most prudent policy is: If you don’t know what it is, don’t touch it. Finally, strong surf and currents can easily wash into intertidal zones, so always be aware of ocean conditions. If the rocks on which you’re standing are wet, you’re in the surf zone.

But the rewards are worth the risks, even for lifelong tidepoolers. John Hoover, a veteran of countless ocean adventures, is amazed at the “richness of experience” that Chela Zabin described: “I was at Punalu‘u black sand beach on the Big Island. There were waves coming in, and it was quite surgy. I noticed something going along the bottom that then stuck to a rock. I looked closer … it was a little golf ball-size octopus. I got closer, and it jumped up into the surge. The surge carried it, and then it hunkered down. I got even closer, and it jumped up and rode the surge again. It was remarkable. All these years, I’ve never seen an octopus like this. This guy was out in the daytime. A surfing octopus,” he says in wonder. “There’s always stuff to be discovered. There’s no end to it.” HH

Thanks to the University of Hawai‘i’s Dr. Isabella Abbott, Erin Cox, Daniel O’Doherty and Joanna Philippoff for their help with photography and species identification.