Dive Dry with Dr. Bill

#494: A S(t)inging Sensation!

Local diver Wade McDonald asked if I'd dive with him sometime following his interview of me on KISL. I agreed and, of course, I keep my promises even though I'm 98% a solo diver and have been since my first dives in 1961-62. I prefer working alone as I can concentrate on finding subjects and filming them without being distracted. We met at the dive park on Monday and decided to head towards the wreck of the Suejac. I've had good luck filming those beautiful shell-less snails known as nudibranchs on the hull, and we did find a clown nudi there.

It was a routine dive and we headed back to the shallows and the dive park stairs when the air in our tanks "suddenly" dropped to 1,200 psi. I decided to stay under for another 10-15 minutes and Wade started to return to the stairs. As I was immersed in filming something, I felt a tug on my fin. Wade was back, telling me to come into the shallows to see something. When I followed him and saw what it was, I was pleasantly shocked. There was a rather large reddish-brown jellyfish in about eight feet of water. When we entered the water we had seen pieces of the oral arms of a large jelly, but hadn't seen the entire creature at that point.

I had never seen this species here before, but thought it was a sea nettle. I knew they arrived in southern California sporadically, and had been somewhat abundant off San Diego back in 2010. I immediately started filming the jelly and tried to extricate it from the feather boa kelp that had a strangle hold on it (and eventually on one of my fins!). Somehow I managed to shoot about 15 minutes of footage with only a small reserve in my tank, but then my head was immersed to a maximum depth of about 5 feet! I thanked Wade for finding this gem. Sometimes four eyes are better than two... whether they be thanks to glasses or to a dive buddy!

When I got home, I looked in my field guide to pelagic invertebrates, the open water drifters. The species was not in the book although a few of its relatives were. I checked the Internet for "sea nettles:" and found that the one we had seen was most likely the black sea nettle, Chrysaora achlyos. It probably wasn't in my older guide since scientists only distinguished it as a species in 1997. It became the largest invertebrate species discovered in the 20th century!

I resorted to the Internet for information (too bad my Harvard classmate Al Gore hadn't perfected it by the time I arrived on Catalina in 1969). The bell or main body is reported to reach a diameter of up to three feet although the one we saw was about two feet. The oral arms may extend another 20 ft. from the bell. Although commonly called the black sea nettle, the color actually is a dark reddish-brown based on my observations.

Although known from at least Monterey (and possibly as far north as British Columbia on occasion) down to southern Baja and mainland Mexico, sightings are rare. When they do appear, it is usually in fairly large numbers with such swarms occurring in SoCal waters in 1989, 1999 and 2010. Apparently these swarms may be connected to red tides, since the plankton found in them are one of the munchies the black sea nettle loves. It is reported they will also eat other sea jellies (known as jellyfish to the non-PC crowd). Yes, these simple creatures are carnivores... ripping apart the flesh of poor innocent zooplankton to grow. The jellies render their tiny prey helpless by zapping them with stinging cells known as nematocysts. They are then transferred by the fleshy oral arms to the mouth and heartlessly digested.

Given its common name of sea nettle, I wasn't sure how bad their sting would be so I stayed clear of the tentacles arranged around the margin of the bell. However, the ripping effect of the feather boa kelp along with the bites taken out of the cnidarian by garibaldi and other fish seeking a spicy appetizer left small pieces floating in the water that contained the stinging cells. My neoprene wetsuit and hood protected most of me from them, but I did feel a number of stings on my partially exposed face. Although definitely "noticeable," the stings were milder than I expected. These sea jellies pose little serious danger to bathers.

As I was writing this column, I received a call from Harbor Patrolman William Flickinger telling me there was one sighted in the harbor. I also heard from bathers that there were several sighted off Pebbly Beach the previous day. Of course being the marine biologist I am, I hope I encounter a few more of them, preferably out in deeper water where I can film them to best effect.

© 2012 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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Black sea nettle freed from the feather boa kelp, bell showing tentacles and oral arms;
oral arms separating from bell and loose oral arm with garibaldi ready to munch.

This document maintained by Dr. Bill Bushing.
Material and images © 2012 Star Thrower Educational Multimedia