Puako's shoreline: Tidepools and turtles

by B. N. Sullivan

Our favorite shore diving site is at Puako, on the Big Island of Hawaii. We used to live in Puako, and we still live just a few miles away, so over the years we probably have made more dives at this one location than at any other place on the planet. Naturally, we have spent a great deal of time exploring the shallow areas along the shoreline there as well.

Puako's irregular shoreline was created by old lava flows. The most recent of these, from an eruption on the Mauna Loa volcano in 1859, flowed to the coast and well into the ocean where it cooled and hardened. Many fingers of black pahoehoe lava are visible along the Puako shoreline today. The rest of the flow now forms a basalt shelf that runs under the surface of the water for some distance seaward from the beach, then ends abruptly as a cliff-like dropoff.

In the photo at right, Jerry is wading on top of the lava shelf near the beach. In the background you can see waves breaking over the dropoff.

The water beyond that dropoff gets deep quickly, but the water depth on top of the inshore shelf is quite shallow. There are many tidepools along Puako's shoreline, thanks to the unevenness of the lava's surface.

The tidepools and shallows at Puako are full of life. There is plant life in the form of algae and seaweed (called limu in the Hawaiian language). There are many species of juvenile fish, which somehow find their way to the tidepools just as they pass from their larval stage into creatures recognizable as tiny fish. They remain in the tidepools until they grow big and strong enough to make their way to the reef community beyond the dropoff. There are creatures like crabs and tiny shrimp and various molluscs living in the tidepools and the near-shore shallows as well.

There is one much larger marine species that can be found in the shallows, tidepools, and even on the beaches and shoreline rocks in Puako. That's the green sea turtle (Chelonia mydas), one of the three sea turtle species native to Hawaii.

Green sea turtles are a very common sight at Puako. They graze on the seaweed that covers the rocks in the shallows, they rest underwater on ledges and in holes in the reef beyond the dropoff, and -- most remarkably -- they haul themselves out of the water along Puako's shoreline to bask in the sun.

Many newcomers and tourists become alarmed when they first spot the turtles on the beach or the rocks at Puako. They assume that the turtles somehow got stuck there as the tide receded, or that they might be injured. Sometimes it takes quite a bit of explaining to convince them that this is the natural behavior of these creatures. The basking turtles are not in distress, and they need no assistance to get back into the ocean. (Honest!)

Actually, no one is quite sure why the turtles bask here. Some scientists believe that the behavior serves as a way to elevate the turtles' body temperature. Others surmise that this is a way to avoid predation, especially by tiger sharks, which are known to favor turtle meals. We always joke that they're just 'working on their tans.'

Green Sea Turtles on the rocks at Puako, Hawaii

When you look at the two snoozing turtles in the photo above, you may wonder why they're called green sea turtles. They don't look green at all! The name comes from the color of their body fat, not the color of their scales and carapace.

In case you are curious, green sea turtles are not known to nest in this area. Most of the turtles that live in the area around Puako are not yet sexually mature. They are at a sub-adult stage of life more or less equivalent to being an adolescent. They spend their time at Puako feeding and lounging around until they mature. Then they migrate some 800 miles to the uninhabited northwest Hawaiian Islands -- especially the area around around French Frigate Shoals -- to mate, nest and lay their eggs. This pattern has been documented through long-term tracking studies of tagged turtles.

If you've ever wanted to see one of these creatures -- or up to fifteen at once! -- Puako is the place to do that. Just don't touch or harass them. Honu, as they are called in Hawaiian language, are a threatened species, legally protected by both Federal and State laws.

UPDATE Oct. 1, 2007: We are proud to tell our readers that this article has been included in the second Carnival of Aloha -- a blog carnival devoted to Hawaii, hosted by Evelyn at Homespun Honolulu. Thank you Evelyn for including The Right Blue, and for your efforts on behalf of Hawaii bloggers. Aloha from the Kohala Coast!