Dive Dry with Dr. Bill

#295: Anchors Away

When you look up and down our coast on a big summer weekend like the Fourth of July, the scene is dominated by hundreds of boats on anchor. For some, that creates an image of many people enjoying our beautiful island scenery and waters. For others it evokes sounds of cash registers ringing. For me, it conjures up images of anchor chains and anchors scraping away at our rocky reefs and the critters that live on them. At least on sandy bottoms an anchor does less damage because the marine life there is accustomed to a shifting substrate, and most are burrowed into it where they are relatively safe. Having seen the damage caused by anchors and chains to sites like Farnsworth Banks and its purple hydrocoral, I become very concerned when the number of boats in our waters is so high. And I can't imagine what damage is done when a cruise ship drops anchor.

Of course divers and dive boats contribute to this damage as well, but most are operated by people who are more aware of the marine life beneath the seas. They usually employ this knowledge to place the anchor where it will do the least damage. Of course good boaters whose focus is fishing are often equally knowledgeable and try to do the right thing. However, we have all seen weekend warriors who have less of a clue about operating their vessels than I have about women.

On a dive at Hen Rock aboard the King Neptune, I decided to dive the outer reef in 50-90 feet. I had some concerns as I submerged and headed in that direction. There were half a dozen boats anchored and fishing nearby, so I'd have to be careful not to be hooked and mistaken for a giant sea bass! I'd be especially unhappy if they tried to gaff and land me! Although I occasionally encounter fishing line at dive sites, and have even been snagged by it, the only time I've ever been hooked was at Casino Point! Yes, hard to believe that a fish hook embedded itself in my wetsuit right inside the dive park, but it did. Of course with all the holes in that wetsuit, it left no significant scars once I cut the leader.

When I reached the outer reef, I started looking for those beautiful shell-less snails known as nudibranchs to film. I often find them at this site, usually indulging in munching... or mating. Their bright colors make them outstanding subjects to record and share with those who view my cable TV show. As I was combing the reef for critters, my poorly focusing and partially color-blind eyes detected an unusual salmon color on the rocks. It wasn't an orange tube worm, or a sponge, or a slab of my favorite fish. It was something I almost never see out in the open.

The salmon color was emanating from the body of a sea cucumber that usually remains well hidden in cracks, crevices and other secure places on the reef. Although they are often very abundant, most divers think they are a form of algae or perhaps some worm since all they see are the feeding tentacles extending out from the rock. In all my decades of diving here, I've only seen a few out in the open. I was surprised when my eyes detected another, then a third and eventually half a dozen of these echinoderms just resting out in the open on the reef.

I started filming them right away, so I didn't realize why they were so exposed. When I paused for a few moments, I noticed that there were freshly broken rocks in the area. I looked up and saw that a section of the reef had been broken by an anchor, probably one whose chain had gotten stuck in the crevice the cucumbers were hiding in. The winch most likely exerted enough force to break the rocks off the reef top, causing the cukes to tumble to the reef base. A few were using the suction from their tube feet to hold onto rock surfaces higher on the reef.

Once I realized what had happened here, I had mixed feelings. The anchor and chain had caused significant damage to that part of the reef. When you consider the number of boats on anchor around the island, this damage could be multiplied many times over... and on a regular basis as boats return to visit the island. However, a part of me was actually "pleased" that the anchor had exposed these echinoderms so I could get some great footage of what they actually look like and share it with you.

Dr. Bob Given first showed me one of these when I moved to the island in the late 1960's. Although this species (Cucumaria salma) is commonly called the white sea cucumber, it's body is anything but white. What most divers see are the dark, bushy feeding tentacles extending out of their protective crevices to capture plankton, small invertebrates and other munchables. You can see a hint of the salmon color where the tentacles meet the body near the mouth.

I don't remember ever seeing a fish nip at the exposed feeding tentacles, but they can be withdrawn into the crevice if one does. Garibaldis love to nip at the tube feet of starfish, so I'm surprised they don't try the same with the tentacles of the related sea cucumber. Some cucumbers contain a toxin known as holothurin in their body walls and tentacles. Perhaps this one does as well, and that is why they don't become an easy meal.

When I researched the white sea cucumber for my recently released "Echinoderms of Southern California" DVD, I was surprised to find very little natural history or ecological information about these extremely common cukes! Perhaps their habit of hiding in the cracks and crevices in nearshore reefs prevented them from being collected often. Unfortunately scientists sometimes drag trawls and other sampling devices over the bottom and reefs, often causing more damage than an anchor would. Those of us who spend our time underwater instead of in a lab surrounded by bottled specimens reeking of formaldehyde, may have to fill in the gaps in our knowledge of these critters!

© 2008 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles," "Gentle Giants: Giant Sea Bass," "Common Fish and Invertebrates of the Sea of Cortez" or the new "Sharks and Rays of Southern California" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Anchor chain running across reef, white sea cucumber in crevice feeding;
white sea cucumber exposed by reef damage from anchor.

This document maintained by Dr. Bill Bushing.
Material and images © 2008 Star Thrower Educational Multimedia