3.10 Contaminants in seabirds
Probably not relevant for Palau at this point.
Seabirds should only be handled by people who have been properly trained.
Seabirds are considered as biomonitors for the marine environments in which they forage. By consuming marine prey, they effectively sample the marine environment. As some species feed on high trophic level prey, they essentially bioaccumulate any contaminants that are present in the ecosystem. Samples from seabirds can be used to monitor environmental pollution of contaminants such as heavy metals, plastic-associated chemicals and agrichemicals. In the past, seabird feathers have been used to monitor the impacts of large-scale oil spills (such as the Prestige oil spill80), by investigating the amount of heavy metal contaminants in chick feathers prior to and for five years after the spill.
Another reason for assessing the contaminants present in seabirds is to assess whether or not they are suitable to eat. Harvesting eggs, chicks, and adult seabirds is a common practice in the Pacific, and as marine foragers they are susceptible to having high levels of certain contaminants that pose a risk to human health. Two harvested species in Aotearoa New Zealand and Australia are Sooty Shearwaters (Ardenna griseus) and Short-tailed Shearwaters (Ardenna tenuirostris). These species are subject to both traditional cultural and commercial harvests, and the presence of contaminants in muscle tissue has been the focus of multiple studies.
Although contaminants have generally been found to be lower than the national standards for food safety in each respective country, 57% of short-tailed shearwater chicks sampled had levels of copper and lead that exceeded acceptable levels81. There may be seasonal fluctuations in the amounts of these contaminants depending on the diets of birds, and routine monitoring should be considered for any seabird species that are regularly consumed.
Method
What samples to take
The part of the bird (egg, muscle tissue, etc) that is consumed is the best sample to take when considering human health implications. Seabirds have the ability to deposit contaminants into their feathers, which are routinely moulted and can lower the levels of contaminants present in the body. For environmental monitoring, feathers are a less invasive sampling method that may better reflect temporal fluctuations in contaminant presence in the ecosystem.
When to use
There have already been numerous studies on heavy metals in easily obtainable samples (e.g., feathers) for Pacific seabirds. This is a good method to establish local baselines, as seabirds forage in different areas at sea.
Testing of harvested seabirds should be done periodically to ensure there have been no changes that may pose a health risk.
Analysis of data
Laboratory analyses of samples will be required. This may involve sending samples overseas, so permitting and permissions are of utmost importance and need to be obtained prior to the project. Data can be accumulated into spreadsheets. Good record keeping is essential for interpretation, so make sure to record all relevant details (date, species, sample type, location data, age of individual, origin of sample, status of individual, storage method for samples, etc) of sample collection and laboratory analyses. Formal statistical analyses of these data are recommended, and the methods used will vary depending on the questions that are being asked. These data can be accumulated over time to undertake comparative work across years, so it is important to have good data management and storage practices that allow for successive operators to use the data as necessary.
Related use of data gathered
- Combined with other ecophysiological data on health of seabird populations.
- Monitoring in response to environmental disasters such as oil spills.