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Dive Dry with Dr. Bill

#719: The Pavilion Ecosystem

Back last winter when we began the planning stages for the construction and installation of Doug Aitken's sculptures in Avalon's Casino Point dive park, one of the questions that intrigued me was what critters would settle on it. Although I dabble in photography, I don't do much real art (unless you ask my 2nd grade art teacher Blanche Bercin who said I could be a great natural history artist). Heck, most artists earn less than marine biologists so I decided to follow the more remunerative path.

Many years ago several of my research projects focused on the way marine life could come to and colonize the island. You might assume it would be very easy for any fish to just swim over (even without GPS). However a number of species are "reef associated" and don't venture out far from the security of the rocky reef or kelp forest.

Now try to imagine a lobster, crab or snail crawling all the way along the bottom from Laguna Beach to Catalina. We all know how slow most snails are (with the exception of abalone stampedes). Even the fastest bottom dweller would have a difficult time descending to 3,500 fsw and getting to the other side within a single lifetime!

Many forms of marine life have a dispersal stage that allows their youngsters to be transported as far from home as possible so they don't get in their parents' hair. Both fish and invertebrates often have planktonic life stages, eggs or larvae, that can drift with the currents over impressive distances.

Now you put something in the water with a hard surface like a boat hull, and most of you know that without adequate bottom paint it will become fauled in no time. Decades ago one of my Harvard roommates, a captain in the US Navy, came over to the island to visit with his wife. I had to get them back into Avalon to catch the boat, so we hopped into my old St. Pierre Michelin design dory, cast off from the mooring and started going in circles. Yep the prop was so encrusted with barnacles and mussels, it acted like a solid ball.

Well, Doug's pavilions or underwater sculptures also have hard surfaces for critters to attach to. We were well aware of that and originally lined up some grad students at Scripps to study the progression of species. Unfortunately that didn't happen so now we are using Catalina Divers Supply (CDS) staff and volunteer divers from the mainland to clean off the critters that attach to the mirrored surfaces.

Due to my surgery and chemotherapy, I haven't dived in over half a year. However, I check with divers who go out to visit or clean the pavilions. Local CDS instructor Mark Guccione reported seeing at least 40 nudibranchs on the sculptures. Based on the description, I thought they might be Doriopsilla but when I saw his images I immediately recognized the spotted dorid (Triopha maculata).

Over my six decades here on the island, I had encountered this species on my dives. However, I was shocked to find I hadn't taken a single second of video of them in the past 17 years! I did find a few still images I took back in the early 1970s in the saltwater tanks in my marine biology lab at Toyon. Strange that I haven't imaged one since then. I wondered why they were now appearing in numbers in the park.

Now nudibranchs (or nudis) are well adapted to colonizing new habitat. They are simultaneous hermaphrodites, meaning they have both male and female sex organs at the same time. All they have to do is meet up with another of their species... and let the fun begin! Mark was seeing white spiral clusters of eggs from these nudibranchs suggesting that in addition to munching, they were also mating in the Macrocystis (giant kelp).

Of course no critter can colonize a new habitat unless it has something to munch on. Therefore the spotted dorid had to be able to fiond food to grow and reproduce. One group I know the spotted dorid salivates for is the bryozoa. Pavilion cleaners have observed species of bryozoa on the sculptures (and cleaned many of them off the mirrored surfaces!). So food is present.

Mark's pictures also showed several other species colonizing the pavilions. One scallop looked more like a traditional pecten, possibly the kelp scallop (Leptopecten latiauratus), than one of our more common rock scallops (Hinnites). I could also make out serpulid tube worms, barnacles and orange tunicates living amongst the algae that covered many of the sculpture surfaces. Hopefully I'll be able to get out there and film these critters with my underwater camera before the sculptures are removed from the park.

© 2017 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Image of Triopha maculata taken in my lab back in the 1960s and photo by Kevin Lee of two munching on bryozoa;
one of Mark's pictures of them from the pavilions and another of Kevin Lee's with spiral egg mass.

This document maintained by Dr. Bill Bushing.
Material and images © 2017 Star Thrower Educational Multimedia