Seagulls may be the unwitting canary in the proverbial coalmine allowing us to monitor oil pollution levels in marine environments more precisely than before, according to scientists in Spain.

Alberto Velando and colleagues at the Universidade of Vigo and the Universidade de Santiago de Compostela, in Lugo, and Daniel Oro of IMEDEA (CSIC-UIB), in Majorca, point out that while oil spills have a rapid and devastating effect on marine wildlife, researchers have also known for many years that large oil spills can increase levels of toxic compounds, including polycyclic aromatic hydrocarbons (PAHs), in the marine environment.

These persistent organic pollutants are not only toxic but have also been linked to certain forms of DNA damage and human cancer, in the laboratory at least. Understanding the long-term implications for raised PAH levels in the marine environment once the cleanup operation is over is therefore crucial to global environmental health.

The Vigo team has turned to the humble seagull, more specifically the yellow-legged gull (Larus michahellis). This species is common in the vicinity of the oil spill caused by the November 2002 wreck of the Prestige off Galicia in North-West Spain, one of Europe's largest oil spills.

The researchers measured PAH levels in the blood of gulls exposed to the oil spill using high-performance liquid chromatography (HPLC) coupled to a wavelength programmable fluorescence detector. They found levels to be twice as high as those in unexposed birds. Levels were determined 17 months after the initial spill, the researchers say.

On the positive side, the researchers found that PAH levels in gulls from an oiled colony decreased by nearly a third in two consecutive breeding seasons (2004 and 2005). "Our findings give support to the nondestructive use of seabirds as biomonitors of oil pollution in marine environments," the researchers add. "Monitoring programs based upon the analysis of PAHs in seabird blood are therefore promising, providing that harm and disturbance to seabird individuals and populations are kept to a minimum."

Environ Sci Technol, in press, http://dx.doi.org/10.1021/es071835d

http://www.imedea.uib.es/natural/goi/seabirds/eng/menuprin/index.html