That Deadly Underwater Debris:

Not long ago, Undercurrent reported on Atsushi Sogabe, a researcher in Japan, who noticed that marine hermit crabs seemed to be trapped by tires. He then did a comprehensive study that concluded absolutely that hermit crabs can be trapped inside tires.

My understanding of tires-as-traps took longer than it should have. I moved to Bonaire in 1980 and started my dive guiding business, Touch the Sea, soon thereafter. On one dive I noticed, inside a tire lying flat on the sand, a hermit crab with hitchhiking anemones, uncommon here on Bonaire; I picked up Shermy the hermy carefully, so we could see him (or her) and his (or her; you get it) anemones more clearly, then of course set him back where he came from, inside the tire. The next afternoon I looked into the tire, and the hermit crab was still there, very convenient for a dive guide! In my orientation, I would explain that Shermy the hermy "lived in the tire." This went on until the next night dive, when, with my light, I looked carefully inside the tire and saw:

• Shermy and his hitchhiker anemones, and

• a few other hermit crabs, and

• several empty snail shells of the type hermit crabs use, and

• pieces of broken hermit crab shells, and

• no algae growing on the bottom of the inside of the tire.

Finally, I realized what I was seeing: trapped hermit crabs that had been eating all the algae they could reach, plus, occasionally, each other. And I had put Shermy back so carefully all those times.

We removed the hermit crabs from the tire and used other debris to construct a ramp so other hermit crabs could climb out.

Hermit crabs are happy to eat just about any animal matter, and plants, too, when necessary - they're the garbage collectors of the oceans. They're extremely versatile in most ways, but there are three things hermit crabs can't do: they can't swim (even without their adopted shells), they can't dig under sand, and they can't climb smooth surfaces. That's why the tires trap them. They're also trapped by plastic cups and other smooth-sided containers.

Okay, maybe you're not charmed by hermit crabs. Do you like turtles?

On an afternoon dive off our Old Pier sometime between 1982 and 2000, I saw a little hawksbill turtle "resting" in a tire. A moment later I realized the turtle wasn't resting. It was struggling to get out of the tire. It had become entangled in what looked like strings but were the disintegrating belts of this steel belted radial tire, still partially attached to the inside of the tire - and the turtle.

In this case help wasn't needed. Before I could grab my shears, the turtle broke free and headed for the surface. Luckily, those steel belts were nowhere near as strong as fishing line, which is responsible for many more deaths of turtles and other critters than steel belt entanglement. Divers are more likely to see fishing line than other trash.

One afternoon I was collecting fishing line and followed it up to something unexpected: a live 9" triton trumpet snail was entangled in the line. It wasn't at the end of the line, where it might have been going after the bait. That triton trumpet was tangled up in the middle of the fishing line, indicating that the line was already lying on the bottom when the triton crawled over it or maybe into it. Its efforts to get free only entangled it more. Times like these really reward you for carrying something to cut line; it took both a little knife and shears to make sure the triton was freed because it stayed tightly closed up in its shell throughout the procedure. Once I had cut through the lines on the outside of the animal, I could gently slide the smaller sections out without hurting the triton.

In the years between 1982 and 2000, I made more than a thousand dives beneath Bonaire's Old Pier (now called North Pier and closed to diving since - you guessed it! - around 2000). Its pilings are covered with glorious natural growth and the bottom around it is "decorated" with trash. The debris is primarily tires, but over those years I saw some notable exceptions.

A beautiful, multi-colored mantis shrimp resting on a piece of discarded rope caught my attention because it didn't bolt away as soon as it saw me. I thought it must be a molted shell until I noticed its eyes were moving. Turns out its eyes were all it could move; that little shrimp's body and legs were entangled in the threads of the rope. I was able to cut through the rope strands until the mantis zoomed away.

Once I disentangled two sponge crabs from a mop head.

Once I found a small goatfish trapped in the pocket of a pair of pants. When it got into the pointy end of the pocket, it was stuck: (most) fish can't swim backwards so it just kept pushing forward until we released it.

Wouldn't it be wonderful if we never saw a speck of debris on any of our dives? Even though I've only seen a few creatures in trouble in all those dives, who wants people to be responsible for any critter's sufferings?

A recent study showed octopuses living in debris items such as metal cans or using trash to camouflage or decorate their den sites. The study raises questions such as whether octopuses were using trash because their preferred den sites of mollusk shells were no longer available, and whether some trash could be harmful to the octopuses. My experiences, mostly with the common octopus and through my tunnel vision, don't bring to mind any likely problems.

Debris dens of benign materials make sense. Almost every pipe beneath our Old Pier provided octopus housing at some time or other. Undersea areas where trash is likely to be are often accessible to divers who collect the trash and discover - in person - how much debris is used by animals including shrimp, worms, sponges, corals, and especially octopuses.

Octopuses have long known that objects made for human convenience are convenient for them as well - consider Greek octopus fishermen, who for centuries lowered clay urns into the sea, waited for octopuses to move into them, and brought up the urns. This doesn't mean we should leave all that human-made debris underwater - human-made items can be dangerous to marine animals in ways we wouldn't expect - but we need to be sure they're uninhabited before we move them!

Dive centers and certification agencies are involved in dedicated debris-collecting dives, with courses and detailed instruction; a lot of good is being done in the aquatic environment that way. But if you're just swimming along and see a plastic cup, you don't have to wait for a clean-up dive to take it away.

Here are some ways to lessen critter deaths from human stuff on a dive:

• Collect fishing line when you can:

• For safety, have a cutting instrument if you're going to handle fishing line. Collect it neatly so you don't entangle yourself, which is potentially dangerous (and definitely embarrassing!). Follow the line as you collect it rather than pulling it toward you.

• Collect small items of recent trash when you can.

• Plastic bags, cloth, and paper smother coral but are easy to carry in my "pocket cleaner station," a net bag (11" x 14" - 28 x 36 cm) that can hold fishing line, cloth, plastic bags, and other debris that's not overgrown. Be sure to evict any animals who are living inside or leave the debris!

• Neutralize articles you can't collect.

• Turn cups, bottles, and other smooth-sided containers upside-down or on their sides.

And now: tires, which are smooth-sided and which definitely don't fit into a pocket cleaner station. The best way we've found, so far, to neutralize tire traps is by creating ramps from inside the tire to the top. I'd love to hear better ideas!

These days, we're reminded not to make contact with the aquatic environment. However, plastic forks and fishing lures are not a natural part of the aquatic environment, and we want to keep it that way, right?

Be forewarned, though: The collecting of debris not only helps the critters, but it changes the diver's relationship with the habitat.

As Antoine de Saint-Exupery might have written, if The Little Prince's planet was underwater:

"It is the time you spend on your reef that makes the reef so important ... You become responsible forever for what you have helped. You become responsible for your reef."

Before moving to Florida in 1980, Dee Scarr received a Masters degree from the University of Florida, and taught high school English, and public speaking and debate. Between 1988 and 1991, Scarr and her workmates tied more than 600 sponges back onto pilings beneath Bonaire's Old Pier in Touch the Sea's Sponge Reattachment Project. Having logged more than 7000 dives, she is a member of the Women Divers Hall of Fame and has written three environmentally oriented books on sea animals and coral reefs.