Ecological impact of the “Erika” oil spill: Determination of the geographic origin of the affected common guillemots

Abstract

Between 80 000 and 150 000 marine birds wintering in the Bay of Biscay were killed during the "Erika" oil spill. Three complementary studies were conducted to investigate the geographic origins of these birds. The common guillemot, Uria aalge, represented more than 80% of the oiled birds and these studies thus focused primarily on this species. Analyses of 184 ring recoveries and biometry of 1851 corpses indicated that guillemots originated from a large geographic area, including colonies from across the British Isles and the North Sea, along with more northern localities. However, the majority of individuals came from colonies located between western Scotland and the Celtic Sea. The third study, based on a population genetic approach using microsatellite markers (samples from dead oiled birds and from more than 600 birds caught in 19 breeding colonies), showed little genetic differentiation among northeastern Atlantic guillemot colonies. This result limits the ability to identify the geographic origins of the birds using only DNA samples, but reveals a significant amount of gene flow among colonies. Overall, results indicate the large spatial scale of the oil spill's impact and underline the usefulness of combining multiple approaches to assess the local and regional effects of such accidents.

Population genetics of the common guillemot, Uria aalge, in the North Atlantic: geographic impact of oil spills

“…Moreover, the results of biometry and ringrecovery analyses following the 'Erika' oil spill show that birds came from a wide area (Cadiou et al 2004), and thus they stress the need to further explore reliable ways to identify the origin of oiled individuals. This study provides important information about the genetic structure and functioning of common guillemot populations in the North Atlantic.…”

“…This is an important wintering area for a large number of seabird species (Mead 1974, Brown 1985, Harris & Swann 2002, and more than 80 000 birds were found oiled along the French coast (Cadiou et al 2004) Société pour l'Etude et la protection de la nature en Bretagne (Bretagne-Vivante -SEPNB) and Ligue pour la protection des oiseaux (LPO). Of these individuals, 80% were common guillemots, Uria aalge (Family Alcidae), of unknown origin.…”

“…Biometric methods are difficult to implement without a consensus on the morphological features to be used to characterize sub-species (Brown 1985). In addition, the spatial resolution of such a method can be imprecise (Cadiou et al 2004). The second potential approach is based on ring recoveries (Baillie & Mead 1982, Harris & Swann 2002, which, while more reliable than biometry, also has some limitations.…”

“…The second potential approach is based on ring recoveries (Baillie & Mead 1982, Harris & Swann 2002, which, while more reliable than biometry, also has some limitations. Typically, few oiled birds carry a ring, and as ringing has been intense in some areas but not in others, any inferences made from such techniques would likely be biased (Mead 1974, Harris & Swann 2002, Cadiou et al 2004. A third approach to determine the geographical origin of affected individuals could be to use variation in the isotopic composition of sampled tissues, a method which reflects the natural variation of stable isotopes in the environment (Hobson 1999).…”

Action plan for seabirds in Western-Nordic areas

“…This both dilutes the impact of a given spill and makes it difficult to identify where the impact is largest. In a few recent cases, genetic analyses have been used in an attempt to pinpoint the origin of seabirds killed during major oil spills (Cadiou et al 2004). In this context, it is also relevant to point out that seabirds breeding in the Nordic seas often winter further south, in areas where they may be exposed to oil pollution (e.g.…”