Dive Dry with Dr. Bill

#179: Farnsworth Bank and the Purple Hydrocoral

Although I've been diving Catalina off-and-on for 36 years, I had two "firsts" on the last weekend in January. The first "first" was that I finally dove Farnsworth Bank. I was really pleased when I heard Scuba Luv's King Neptune would be heading out there that Saturday. I'd looked forward to diving this site for decades because I wanted to see and film the purple hydrocoral located on this deep bank. I had my diving gear set up for the dive, and knew it would probably involve a maximum depth in the range of 150 ft.

Farnsworth Bank is a sea mount or series of underwater pinnacles located about one and a half miles from Ben Weston Point in the open ocean off Catalina's windward coast. Depths here range from a high peak at about 60 feet down to the basement depth of about 300 ft. The Bank was named after legendary Avalon fishing boat captain George Farnsworth, son of Samuel Farnsworth who engineered the road out of Avalon into the interior (hence Farnsworth Loop). Farnsworth is credited with developing the technique of using a kite to skip bait across the ocean surface, and reportedly could catch fish when no one else could. He was a much sought after guide who spent most of his time with William Boschen, an early member of the Tuna Club noted for catching more broadbill on rod-and-reel than any other fisherman.

A diver named Ross Overstreet has created a very interesting web site about Farnsworth Bank. He has used one of my favorite technologies, a geographic information system (GIS), to create a three dimensional model of the submarine topography of Farnsworth. For those readers who are divers or fishers with Internet access, you may be interested in checking this out at his web site I used Ross' images to plan my dives at Farnsworth and also incorporated them in a recent video showing on my Catalina Cable TV show.

The day was calm and the trip out to the Bank uneventful. It was pretty amusing when dive master Chris asked me, as one of the more experienced local divers on board, to describe the dive site. I had to reply "Chris, I'm a virgin on this site." Yes, I'd never made it out to Farnsworth on a day when diving was possible. Despite a NW swell and current at the site, it was still quite dive able that day. "Today's the day I'm gonna make it happen" (with apologies to the Pointer Sisters, but I was so excited).

Farnsworth Bank is a marine conservation area designated back in 1972. It was so designated in large part due to the extensive population of purple hydrocoral Stylaster californicus (formerly Allopora californica). Harvesting and take of this hard coral is strictly prohibited. The color of this hard coral is due to the presence of a red carotenoid pigment, astaxanthin, mixed with calcium and protein. The color actually may vary from purple to pink to deep blue.

One of the divers from the Monterey area wanted to buddy up with me on that dive. At first I was quite hesitant, since a buddy can also become a liability should they have problems. He appeared to be an experienced diver and was well equipped. I was concerned because he was diving Nitrox, a gas mixture with a higher percentage of oxygen than regular air. The increased oxygen meant that he could not dive to the depths I planned without risking oxygen toxicity. However, he assured me he was okay with that and would stay above me as I filmed at depth, and then I'd join him at the 100 ft plateau of the site.

We went down the anchor line and it seemed to take forever to get to the high point. I hit it at a depth of 146 ft and immediately started filming to maximize the footage given the short safe bottom time limit. Although the visibility had been only fair in the upper 80 ft, it did open up to about 50 ft at my maximum depth. This was good enough for me to film the beautiful purple hydrocoral that dominates this formation. Because these hydrocorals are brittle and easily broken, I could not stabilize by lying on the reef itself and had to hover above or alongside to get the video footage I wanted. The current and surge made this a little difficult.

Purple hydrocoral feeds on plankton. It is often considered an indicator of strong currents which bring this food in. On our dive the current was steady but quite manageable. If you look closely, the hard skeletons of the colony are pierced by many small pores or openings. Two kinds of polyps are found in these pores: ones that feed and others that serve to defend the colony against marine life that might try to settle on it or eat it.

The purple hydrocoral is a slow growing cold water species found from northern California to Baja California. It is found on rocky reefs and offshore banks, especially in the southern California Channel Islands. This species may take 25 years to grow the length of my little pinkie, and hundreds of years to form some of the large colonies present at this site. It is possible some colonies may live thousands of years, dating back before the birth of Christ (or Mohammed or even L. Ron Hubbard in case the lovely Katie Holmes is reading this). Colonies are formed from a fairly brittle calcium carbonate skeleton. Because of this they are sensitive to damage from anchors, fishing gear including dragged nets, or the fins of bouyancy-challenged divers. Hydrocorals are in the same class as the hydroids rather than grouped with the reef building corals of tropical waters, although both belong in the same phylum (Cnidaria).

I have often wondered why there were no mooring buoys at Farnsworth Bank. Given the extreme sensitivity of the hydrocoral here, mooring buoys would greatly reduce the damage done by anchors from dive and fishing boats at this site. Such buoys are used extensively on the coral reefs in places like the Florida Keys and make a lot of sense. The reason appears to be that mooring buoys would create issues regarding who can use them and who will maintain them. Another reason stated is the concern that having mooring buoys here would increase the number of divers (and fishers) on the site and therefore potential damage due to increased visitation.

© 2006 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. 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, "or "Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

Ross Overstreet's submarine topography of Farnsworth Bank, pink colored purple hydrocoral showing individual pores;
purple colored hydrocoral colony, purple hydrocoral damaged by anchor, divers or fishing gear.

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia