Seabirds on remote islands are contaminated with lead and selenium

On remote islands dotted throughout the oceans, millions of breeding seabirds seek sanctuary from predators and people. But even here the wildlife is not immune to human activity occurring thousands of kilometres away on the mainland. 

New research, published in the journal Environmental Science and Pollution Research, has found that seabirds are being exposed to elements such as lead and selenium at potentially high enough concentrations to start causing problems.

A team of researchers analysed feather samples belonging to different species of gadfly petrels living on four islands dotted throughout the southern hemisphere. There are about 35 species of petrels belonging to this group - the researchers were able to obtain feather samples for seven of these.    

Dr Alex Bond, the Senior Curator in Charge of Birds at the Museum and co-author of this study, says, 'Petrels in general are relatively poorly studied. We don't know a heck of a lot about them as they breed on some of the most remote and inaccessible islands in the world.

'Not only that but the birds are typically nocturnal and usually breed in burrows. This means that actually sampling them is rather tricky.'

This research suggests that more attention should be being paid to these birds. At their position near the top of the food chain, they could be signalling a much wider problem that is occurring in these isolated environments. 

Lead poisoning

Even since the Roman era, when water pipes were made of lead, people have been aware of the damaging effects of the metal on human health.

But this has not stopped its widespread use in many parts of society right up to the present, as it continued to be found in shotgun shells, paint, petrol and even makeup.

It's not only humans who are being affected by the prevalence of lead in the environment. During the last century the impact of lead on wildlife has become more and more apparent.  

'With elements such as lead, it can cause all sorts of physiological problems,' explains Alex. This can include weight loss, lethargy, reduced chick growth and even blindness. 'But can also it can alter a bird's behaviour, which can be critical for species with complex mating systems.'

There is now good evidence for how lead poisoning affects birds of prey, as they eat carrion that is tainted with lead shot. This led to a large-scale campaign to restrict the use of the metal in both shooting and fishing, although in many places it is still in use.

The concern for our own health resulted in leaded petrol being phased out in many countries around the world, but it can still be found in use in several other regions.

But how high concentrations of lead impacts seabirds - and petrels in particular - is still not really known.

As lead and other elements such as selenium are emitted into the atmosphere through both the burning of leaded petrol and heavy industry, they are carried up into the atmosphere. This is then transported by air currents over even the most remote oceanic islands.

When it then rains, these potentially toxic elements are brought back down to Earth and enter the food chain. As predators eat animals that themselves have consumed small amounts of these elements, the level of lead and selenium accumulates in the predators' bodies.  

'We don't really know at what point these elements start causing problems in petrels, ' says Alex. 'It depends on the species, the sex and a whole bunch of other aspects, but we can start to make some relatively informed conclusions.'

Unknown impacts

Similar to how hair contains a chemical record of the drugs a person may have taken, the feathers of birds contain a record of certain elements that they have been exposed to.

This has allowed Alex, Susie Philpot (lead author and MSc student) and their colleagues to take feather samples from petrels and then test them for three different elements: zinc, selenium and lead. 

'For some of the species we found that the levels of selenium were really high,' says Alex.  'It was quite significantly above where we think effects should be starting to show.

'We expect too much selenium to be somewhere around five parts per million. Some of the individual birds we measured had concentrations of 84 parts per million.'

Lead painted a similar picture. While problems are typically expected when levels reach four parts per million, some birds tested were found to have a concentration of 63 parts per million.

The impact this might be having on the petrels is still unknown. Many of the petrel species studied are either endangered or vulnerable, but it is important to note that this is most likely due to other factors.

'The cause of their conservation status is not, at the moment, related to anything around contaminants,' explains Alex. 'It is mostly related to invasive species on their islands driving the populations down.'  

Rats and mice that were introduced onto these offshore islands are currently wreaking havoc as they attack the native seabirds and chicks. But this research has shown that even if these immediate pressures were removed, that doesn't necessarily mean that the species will recover.

Dealing with problems such as heavy metals swirling around in the atmosphere is a much tougher task, and one that will take far longer to solve.

The team hope that now they have begun to scratch the surface, the research will finally help us to understand the full impact that heavy metals are having even in these remote corners of the oceans.