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Dive Dry with Dr. Bill

#690: Withering Away

This winter seems to have been an unusual one in terms of pathogens. You know, those cute little buggers that enter our bodies and turn them upside down. I generally have a pretty good immune system and rarely get sick, but over the past three months I've had three bouts with flu-like symptoms and several colds. It makes me wonder if someone is genetically engineering new strains and releasing them here.

These microscopic bacteria and viruses are often overlooked members of our natural ecosystems, too. Landlubbers often pay no attention to them unless they get an infection while swimming or after drinking unsanitary water. Even marine ecologists like myself may miss the signs since we are usually looking at the "bigger picture."

Back when I first arrived on the island in the late 1960s, abalone were so abundant I thought they'd always be here. Of course we completely overlooked the black abalone (Haliotis cracherodii). Because it lived in the upper subtidal and was exposed to stronger wave action, it had a tougher foot muscle than the more tender pinks and greens and especially the whites that lived at much deeper depths.

In my early Toyon days our school had the archaeological permit for the island and conducted a number of digs at various sites. As the school's marine biologist, I often went along to identify the remains of critters found in the Native American kitchen middens (or trash dumps). Once at Little Harbor we found a pristine midden chock full of black abalone shells. Obviously the indigenous people chowed down on this species, which was probably easier to take since Jacques-Yves Cousteau (and Emil Gagnan) hadn't been born yet and there were no SCUBA air fill stations on the island back then anyway. Speaking of which, I've also found middens submerged under water with many abalone shells exposed by currents and storms.

Then, during the intense El Niño of the early 1980s, abalone began disappearing altogether. Blacks, pinks and greens were no longer common in our waters. It took some time for scientists to determine the cause for this die-off. It was an epidemic of a tiny bacterium.

This bacterium infects the inner lining of the abalone's gut and impacts the production of the digestive enzymes necessary to break down their ingested food. The abalone no longer can extract sufficient nutritional value from the giant kelp and microalgae it has ingested. In essence it begins to starve.

When external sources of energy are restricted, an animal relies on fat and body tissue for sustenance. Now I have plenty of bioprene (aka blubber) to sustain myself thanks to my own disease, VET (Video Editing Tummy). Sometimes I wish an equivalent of the withering syndrome bacterium would infect me for a few months. However, abalone are not known for their fat content.

Instead the abalone turns to its reproductive and muscle tissues, breaking them down to provide the necessary nutrients to sustain life. Obviously reproduction will be curtailed if the gonads and gametes are being digested. Likewise the foot muscle that allows the ab to cling to the rock will deteriorate and wither away. When the foot withers, abalone can no longer hold on tight and are more vulnerable to predation. If they don't succumb to a hungry critter, they may simply starve to death.

Withering syndrome was prevalent during that previous El Niño. However the bacterium may be present in an abalone but not cause death especially during periods of cooler water. In fact Andrew Harmer has shown me images of healthy (and infected) black abalone in colder waters north of us. He suggested withering syndrome may be on the rise up there. Warm water events like the past two years may trigger an epidemic again even in those snails which have resisted.

I have mentioned seeing empty shells of abalone in our dive park lately. Given the sharp decrease in giant kelp, one of the abalone's main food sources, and the presence of the far less palatable devil weed (Sargassum horneri) abalone may already be starving due to lack of food. If the withering syndrome bacterium is also affecting them, they may be in double trouble after showing signs of recovery prior to the warming event. I may have to wait until my next incarnation to satisfy my carnivorous taste for an ab burger.

© 2016 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 abalone on Catalina shore from early 1970s and healthy ones from the San Luis Obispo area (courtesy
of Andrew Harmer); the tasty feet of green abalone back in the days you could take them.

This document maintained by Dr. Bill Bushing.
Material and images © 2016 Star Thrower Educational Multimedia