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Dead Sea 

An unpublished study shows the surprisingly lethal effects of the Cosco Busan oil spill. Why are government scientists helping the ship's owner keep it a secret?

Wednesday, Feb 24 2010
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In the wake of the accident, there was already evidence, albeit inconclusive, that pointed in this direction. Previous scientific studies had established that bunker fuel, a highly processed version of crude oil, was dangerous to various forms of marine life. (The oil takes its name from the bunkers that were used to store coal, which freighters once used as fuel.)

After the Cosco Busan spill, federal and state researchers performed a preliminary survey of stretches of shoreline subjected to heavy oiling on the northern side of the bay, below the chain of upscale tourist towns known as the Marin Riviera. Their observations indicated that at these sites — which are also prime spawning grounds for herring — something was very wrong.

At Sausalito, only 44 percent of herring eggs sampled hatched successfully during the winter of 2008. At Peninsula Point, the hatch rate was a startlingly low 24 percent. By contrast, at San Rafael Bay, which was not polluted by oil, some 84 percent of eggs hatched.

The newly obtained report reveals that researchers returned to these oiled sites in the winter of 2009 to see whether things had improved. The opposite had taken place: Herring had not spawned at a single site that had been oiled.

These observations pointed to the need for further and more rigorous study of the spill's effects. Bunker fuel had fouled the bay's shoreline, and many herring embryos had died off months later; this much was known. Missing was proof that the fuel itself had caused this environmental catastrophe, and not some biological fluke in the herring population or unusual conditions in San Francisco Bay.

Bodega Marine Lab is where scientists tried to demonstrate that link conclusively. The 51-page study obtained by SF Weekly, "Data Report of Laboratory and Field Herring Injury Studies Performed 2008-2009," chronicles their efforts and the results.

The study sought to mimic, in a controlled setting, the spawning conditions preferred by herring in the bay's "intertidal zone" — the shallow, gravelly areas close to shore where the fish like to lay their eggs. At the lab, water was leached through containers of gravel that had been exposed to different concentrations of oil, then passed over incubating herring eggs.

The study, conducted from January to March 2009, was distinguished by attention to a few key factors. In addition to comparing eggs exposed to the bunker fuel used in the Cosco Busan to those in clean water, scientists examined groups of eggs dosed with crude oil of the sort that fouled Alaska's Prince William Sound during the Exxon Valdez spill.

They also exposed some eggs to ultraviolet light in the hope of learning more about the poorly understood phenomenon of bunker fuel's "phototoxicity" — an intensifying of its deadly properties as a result of chemical changes that come with exposure to sunlight. Such effects could be particularly important for herring, which, like other species of fish — including anchovies, jacksmelt, and the California grunion — lay their eggs in shallow water where sunlight penetrates easily.

The results of this research, as presented in the data report, were stark. Water contaminated with bunker fuel of the type that leaked from the Cosco Busan was found to lead to higher rates of embryo death and birth defects than either clean water or that polluted by crude oil. Among the abnormalities observed were scoliosis, bent heads, deformed jaws, and eyes that had basically dissolved in their sockets.

In the third of four trials performed — because of the water conditions and number of variables measured, the report identifies this as the most definitive experiment — the highest dose of crude oil resulted in a 16 percent rate of necrosis, or desiccation and death of cell tissue, among embryos. Less than a third of that dose of Cosco Busan oil had the same effect.

When the dose of Cosco Busan oil was increased to equal that of crude oil, more than 90 percent of fish embryos exposed to it experienced necrosis — a staggering fivefold increase over the damage wrought by crude oil under the same conditions.

Bunker fuel's poisonous qualities were found to be exacerbated by exposure to sunlight. In the first trial, only 1 percent of embryos hatched alive after being exposed to both a one-part-per-thousand concentration of Cosco Busan oil and ultraviolet light. By contrast, about 66 percent of those exposed to the same amount of crude oil and UV light hatched. In subsequent trials, not a single live fish exposed to both UV light and the highest concentration of Cosco Busan oil emerged.

Scientists had set out to measure, in a laboratory setting, the effect of oil like that spilled by the Cosco Busan on gestating fish. It seemed they had an answer. Bunker fuel, for herring embryos, was a startlingly effective poison.


The evidence government researchers found on the poisoning of fish embryos that results from a combination of bunker fuel and sunlight is striking — the closest thing yet to a smoking gun in the mysterious die-off of herring in San Francisco Bay following the 2007 spill. The information is of pressing interest to any member of the public curious about just how much damage the Cosco Busan did to the living creatures of the bay.

Yet state and federal scientists have been extremely reluctant to release or even discuss the results of their research. Their reticence raises questions about the regulatory apparatus at work in the case — an ethically murky system whose shortcomings are highlighted, in particular, by federal and state officials' handling of the 2009 study on the toxicity of bunker fuel.

About The Author

Peter Jamison

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