Marine researchers have found oil spills in marine habitats can damage fish populations even more than was previously thought. Dr. Gary Cherr from UC-Davis is one of the researchers and he agreed to an interview which is below.
Your research on the 54,000 gallon Cusco Busan spill near San Francisco, found oil spills could be much worse for the environment than previously thought – what did you uncover that shows oil spills are worse?
The fact that naturally spawned embryos in the spill zone showed almost complete mortality in the shallow water due to sun/oil exposure was unexpected considering the small amount of oil spilled and the complete lack of visual oil in these zones 3 months after the spill. As such, these were very low exposures that at worst would have caused developmental abnormalities in the absence of sunlight. With sunlight, the residual oil in tissues became incredibly toxic causing embryos to essentially dissolve.
Immediately what comes to mind is the Gulf oil disaster – is phototoxicity likely playing a role currently in the Gulf in terms of damaging fish embryos, and therefore reducing fish populations?
Undoubtedly, since most crude oil has some phototoxicity (albeit less so than bunker fuel oil). Problem was that nobody did any field assessments of this or lab exposures to date. Hopefully the latter happen with studies upcoming.
How long can phototoxicity remain a problem in a marine habitat after an oil spill?
Depends on how long the specific chemicals that are phototoxic remain. With Cosco Busan, we saw the developmental abnormalities in the following 2 years but did not observe phototoxicity. Could be because the phototoxic chemicals in bunker fuel had been degraded after the first year. This needs much more research in order to understand why phototoxicity changed but oil-induced developmental abnormalities persisted for 2 years.
How can you measure phototoxicity in the Gulf today, and are there plans to do so?
Without oil present in the photic zone, this cannot be done now in the field, unless an assessment surrounding a very small spill can be done. Probably needs to be studied in controlled lab setting using the Macondo well oil.
When the federal government said most of the oil was gone, but later research showed it wasn’t because a large portion had sunk to the bottom, what can be done to better understand how little oil present in water can still be toxic to fish when exposed to sunlight?
At depth it will not be exposed to sunlight. However, it is still very toxic and will impact benthic and deepwater organisms as long as it persists.
Is it possible oil that sinks to the bottom of a body of water can remain there for years, leaking small amounts into the larger body?
Yes. Oil is not very water soluble, but a small fraction of chemicals are. These can continually diffuse away from the mass of insoluble oil. In the Gulf, the depth is too great for much to come to the surface. In shallow water situations though, this can be significant. Fortunately, petroleum-degrading microbes in most locations are pretty efficient at degrading the oil. An exception was the Exxon Valdez spill in Alaska where oil persists over 20 years later primarily because the very cold temperatures slow microbial degradation.
Will you be continuing the phototoxicity research to better understand its effect on marine life, or do you have enough information at this point?
Together with our colleagues at NOAA (John Incardona) we have conducted some follow up work which will be published in the next week or two in the journal PLoS ONE (Incardona J, et al. (2011)
“Potent phototoxicity of marine bunker oil to translucent herring embryos after prolonged weathering.” PLoS One, in press.). Also see the article attached as well.
“Natural sunlight and residual fuel oils are an acutely lethal combination for fish embryos.”
Hatlen K, Sloan CA, Burrows DG, Collier TK, Scholz NL, Incardona JP.
Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle, WA 98112, USA.
Image Credit: United States Coast Guard, Public Domain