OIL and wildlife aren’t usually a good mix. Just look at the many ecological disasters around the world triggered by oil spills. When the tanker Prestige broke up and sank off north-west Spain in late 2002 it polluted 400 kilometres of coastline and damaged fisheries. Three years earlier, tens of thousands of seabirds were killed by a spill from the Erika off the coast of France. Perhaps most notoriously, the grounding of the Exxon Valdez in 1989 caused havoc to a pristine stretch of Alaskan coast.
In light of such events, “oil ecology” sounds like an oxymoron. Yet there is life in oil, and some species of insect even seem to thrive in the stuff. The most remarkable of these is the petroleum fly, observed in places like the Rancho La Brea tar pits in Los Angeles. First spotted more than a century ago, this fly Halaeomiyia petrolei (formerly known as Psilopa petreoli) feeds on insects that get stuck to the surface of oil or tar pools. The fly’s larvae, known as oil pool maggots, spend almost all their time submerged in the oil, surviving on oil-eating bacteria and organic debris.
The petroleum fly has long been a source of interest for researchers intrigued by its ability to survive amid toxic fumes that would kill off other species. How does it do it? The key lies with the microbes that live in the larvae’s gut. Given that their guts are full of asphalt, it seems remarkable the microbes survive at all. They do so because they are solvent-tolerant, able to metabolise hydrocarbons. Researchers are now hoping that these microbes might point the way to dealing with carcinogenic polyaromatic hydrocarbons found in industrial emissions and car exhausts.
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“There is life in oil: some species of insect thrive in it”
Surprisingly, oil-rich environments can host a rich mix of plants, which in turn attract wildlife. At some tar seeps in arid central California, you can find anything from California Pacific blacktail deer to assorted birds and insects, and there can be greater biodiversity than in the surrounding area. That’s because as oil rose to the surface, losing its volatile components and emerging as viscous tar or asphalt, it brought water with it. Water is a by-product of natural oil production which usually remains trapped under layers of impervious rock, but in these rare circumstances local geology allows the water to rise with the oil.
Animals feeding in these oil oases should beware, however. The tar pits at La Brea contain the fossils of numerous mammals and birds that became trapped in the sticky goo. It is thought the animals died of starvation or exhaustion or were eaten by passing predators while stuck fast. Up to 50 litres of asphalt still ooze to the surface every day, trapping birds and small mammals. Not that this will seem surprising to anyone who has witnessed the aftermath of an oil tanker disaster.
