The relation between pollutants and disease in guillemots

Ecotoxicological and pathological studies of common guillemots Uria aalge beached on the Belgian coasts during six successive wintering periods (1989-90 to 1994-95)

Guillemot covered with oil © Diederik D'Hert

Context of the study

Within the frame of the third European North Sea Conference a program was found to monitor the health and causes of death of sea birds and marine mammals. In Belgium the common guillemot is by far the most abundant of all overwintering species (for both marine birds and marine mammals). For this reason it became the focus of this study. Although there is a lot of information available on contamination of sea birds by heavy metals and organochlorines, little is known about how this contamination relates to diseases or deaths.

Content of the study

Healthy guillemots © Per Harald Olsen

During six successive winters 727 common guillemots were collected from Belgian beaches. Some were found death on the shoreline, others where still alive but died during rehabilitation. Besides being monitored for general condition (weight, fat content,...) and traces of oil on their feathers, half of these birds were sampled for heavy metals and PCB content.

Main results of the study

Half of the collected birds showed external traces of oil. Even small traces of external oil can seriously impair the overwintering birds' isolation, and therefore their changes for survival. 75% of the studied birds were exhausted: they showed a strongly reduced pectoral muscle and a low fat content. These birds contained higher concentrations of PCBs in their livers. This may be the result of remobilization of these toxines after depletion of the fat reserves where they were previously stored. The exhausted birds were also more heavily contaminated with copper, zinc and mercury.

The study concludes that non of the examined pollutants were considered as an unique and direct cause of death. They might however cause additional stress leading towards weakness and death of the part of the overwintering population. More research is necessary to determine the actual effects of these pollutants on the health status of the guillemots.