Scientists have identified a microscopic sea creature with a Jekyll and Hyde personality as the culprit in the death of tens of thousands of abalone three years ago along the Sonoma and Mendocino coasts, but they don't know how to stop the elusive critter from killing again.

The toxic "red tide" in 2011 turned the pristine coastal waters into a graveyard, with the rotting carcasses of red abalone, sea urchins, starfish and other mollusks strewn along the shoreline from Bodega Bay and Fort Ross to Anchor Bay in southern Mendocino County.

A team of scientists and geneticists said this week that they used a sophisticated, new forensic genome testing technique to pin the carnage on a mysterious poison-producing micro-organism known as Gonyaulax spinifera, a species of phytoplankton virtually unheard of in this part of the world.

Laura Rogers-Bennett, the senior environmental scientist for the California Department of Fish and Wildlife, said the creature is as bizarre as it is deadly. Its modus operandi, she said, is to suddenly appear in large numbers, produce mass quantities of deadly Yessotoxin and then retreat into tiny invasion-of-the-body-snatcher-type pods until ocean conditions are ripe for another rampage.

"One part of this organism's life cycle is when it becomes a cyst, like a spore or seed, that sits on the bottom," said Rogers-Bennett, who is also a research associate for UC Davis' Bodega Marine Laboratory in Bodega Bay. "When the environmental conditions become optimal - and we don't know what those conditions are - these cysts can burst out of their little seed pods and come back to life. The worry is that when they bloom we get these giant red tides."

Blooms not always toxic

The conundrum, Rogers-Bennett said, is that the blooms aren't always toxic. In fact, deep ocean upwellings that produce blooms of phytoplankton like these ones are mostly beneficial, she said.

"It's the food at the base of the food chain that larval fish and the larvae of shellfish eat, so 99 percent of the time they are the good guys," Rogers-Bennett said. "The bigger fish then eat the larval fish and so on up the food chain, so these blooms are critical and important in the ocean."

The effort to find out why certain blooms are good and others are bad has recently become a bit of an obsession among marine biologists. That's because previously unknown blooms of toxic algae are suddenly proliferating along the California coast, killing wildlife and increasing the risk of human sickness. The blooms, often involving different organisms, have recently been bigger and have occurred more frequently than before.

The intensive effort to find out what caused the die-off in 2011 led to at least one significant advance, which is detailed in a study published in the April 16 issue of the scientific journal Nature Communications.

The report, which Rogers-Bennett co-authored, talks about how forensic genomics was used to track down and pinpoint the elusive Yessotoxin killer. The hunt got an unexpected assist from biologists who fortuitously had taken tissue samples from red abalone for another experiment before the mass deaths.

The forensic team used a high-powered computer to compare hundreds of thousands of abalone genes from before and after the die-off. The scientists found alterations in 30 genes, some of them unknown to science, and determined their function was to detoxify the body after a Yessotoxin attack, Rogers-Bennett said.

New genetics method

"This is a brand-new genetics method. We were able to look at all of the genes, which we were never able to do before," she said. "We were able to identify the cause by identifying what's different before and after. I think this method is going to be used for a whole suite of natural events that hit wildlife. It's broadly applicable."

It is one of an array of sophisticated ocean-monitoring technology, including robotic gliders, a network of underwater sensors and satellite observations that are being used to track recent changes in the ocean ecosystem and, hopefully, determine whether global warming is playing a part.

The problem is that scientists still know very little about Gonyaulax or the Yessotoxins they produce. Marine biologists say the popular term "red tide" is a bit of a misnomer because toxic blooms are not tides nor are they always red.

Red abalone can still be harvested for personal consumption if they are the appropriate size and no scuba gear is used. The depleted fishery, however, prompted new regulations. Fort Ross, historically one of the most popular abalone-diving sites, is now closed. Abalone divers can take only 18 abalone a year in California compared with 24 in previous years. Only nine of those can come from Sonoma County, Rogers-Bennett said.

The good news, she said, is that there were no significant die-offs in 2012 or 2013, but, again, no one knows why.

"The mysteries of the ocean is what keeps me interested and in this job," Rogers-Bennett said. "We know so little about the ocean that we are discovering new things all the time."
