日本海で油汚染死したウトウ <i>Cerorhinca monocerata</i> の体付着油と消化管内黒液のガスクロマトグラフ法による分析

We analyzed 44 Rhinoceros Auklets impacted by the oil spill along the Tsushima Warm Current off Shimane Prefecture, southern Japan Sea in January 1986. All of the carcasses had been oiled with an average of 128g oil weight (ranging from 12 to 300g), which accounted for an average of 31% (ranging from 4 to 72%) of the body mass, and with an average of 40% oiled area of the body surface with wings extended (ranging from 10 to 95%) (n=38). Among the 44 oiled birds, six birds had a few scales and/or vertebrae of fish in digestive organs, but the remaining 38 birds contained no food items. The non-oily blackish liquid contents were found in digestive organs from 34 birds, while blackish liquid was not found in either the esophagus, stomach or intestine of the remaining 10 birds. Neither the presence of the blackish liquid nor the volume found within the digestive organs were correlated with the weight or the area of the oil adhering to the body. This showed that the mortality of oiled birds was independent of the amount of oil adhering to the body and was also independent of the presence or volume of blackish liquid in digestive organs. The oil adhering to the body was detremined to be heavy oil; however, the blackish liquid from within the oiled birds differed greatly from the external oil as seen by gas chromatographic analysis and was considered not to be composed of the n-alkanes identified in the oil adhering to the body or in the oil spilled in the sea. The n-alkane distribution was, however, very similar in the lighter alkanes around C₁₉ and in the phytane and pristane of biomarkers to the liquid contents found in the dead non-oiled bird of the same species washed up on a Pacific-facing beach in central Japan. Petroleum composition analyses, with large sample sizes, of alimentary liquid found in seabirds are needed to clarify the extent to which oil-pollution affects seabirds around Japan in areas that have experienced accidental oil spills and in those that have not.