Nudibranchs Track El Niño Events
Researcher:
Jeffrey Goddard
Research Biologist
Marine Science Institute
UC Santa Barbara
E.:goddard@lifesci.ucsb.edu
T. (805) 688-7041 / 893-7245
Tools:
Revised:
December 10, 2008
Okenia rosacea, a dorid nudibranch that gets its color from the red bryozoans it eats. Photo: Gary McDonald
December 10, 2008
Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334
Hermissenda crassicornis, one of the most abundant aeolid nudibranchs in California. Photo: Gary McDonald
Nudibranchs are brightly colored shallow-water mollusks whose odd shapes may remind you of the flowery things on your grandmother’s swim cap – if her cap had been neon.
The animals, typically only a few centimeters long and not being fleet of foot, prey on sessile (nonmoving) critters such as hydroids, sponges, bryozoans and anemones.
With funding from the Ocean Protection Council and California Sea Grant, marine biologist Jeffrey Goddard of UC Santa Barbara and colleagues are exploring what the historical nudibranch distribution tells us about past coastal conditions. The theory is that the abundances of these short-lived mollusks create what amounts to a six-month low-pass filter of ocean conditions and their effects on rocky intertidal and sub-tidal ecology.
Triopha maculata, a dorid nudibranch that feeds on bryzoans. Photo: Gary McDonald
Now a year into the three-year study, Goddard and colleagues report an interesting discovery that may allay concerns about the apparent loss of these animals along parts of the coast: El Niño events seem to favor intertidal nudibranchs in Monterrey, Santa Cruz, Half Moon Bay and Duxbury Reef. That is, there are more of these snail-like creatures during El Niño events, fewer during colder La Niña events.
In the historical record, intertidal nudibranch numbers double or triple during El Niño, as compared to La Niña, Goddard says, but not because of warmer water temperatures.
“We think the nudibranch pattern reflects changes in the transport of surface waters along the coast,” he says. “During El Niño, there is a relative onshore transport of surface waters that might carry more larvae to shore.”
Doriopsilla albopunctata, a dorid nudibranch that feeds on sponges. Photo: Gary McDonald
That is the theory at least.
“The real test of our hypothesis will be when we get another El Niño,” Goddard says. “Then we will be looking to see whether nudibranch numbers increase dramatically as predicted and whether we can measure enhanced onshore flow of their larvae.”
“People were worried that nudibranchs were disappearing and they wondered why. Our results go a long way toward explaining this, given the recent La Niña conditions.”
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