After the Spill

Oil spills leave environmental hazards long after clean up.

Imagine a boy enjoying a seemingly healthy childhood despite living in a city rife with smog. The years pass and the the boy grows and moves away to the fresh air of the country, only to develop smog-related respiratory issues years after exposure. This situation is well known to happen in humans, yet research from Scripps Institution of Oceanography has uncovered an environmental analogue in corals.

In April 2012, Aaron Hartmann, SIO M.S. ’10, Ph.D. ’14, was a graduate student finishing his final field season on the Caribbean island of Curaçao when an oil spill covered an area roughly the size of 30 soccer fields. The spill occurred just weeks prior to the annual spawning season for many corals, prompting Hartmann and colleagues to test how lingering oil contamination affects corals during their earliest life stages.

Their research concluded that the oil spill profoundly affected the ability of coral larvae to transition to their adult stage, and that this response only became apparent after, rather than during, the time when larvae were
exposed to oil-contaminated water.

When corals reproduce, their eggs amass at the sea surface and, after fertilization, larvae swim for days near the surface before they “settle” down to the reef and become adults through metamorphosis.

Rather than test only the immediate and direct effects that toxins have on the animals, Hartmann and colleagues examined the response of larvae during and after exposure to oil. Higher larval death rates arose more than a week after exposure to oil had ended. In addition to killing larvae, oil exposure dramatically hindered the ability of larvae to settle on the seafloor, causing added stress to a species already endangered by development, overfishing and disease.

“The greatest limitation of environmental impact assessments following catastrophic events is that most aren’t designed to measure damage to ecosystems beyond the immediate aftermath,” says Hartmann. “We found that long-term ill effects of oil contamination on coral larvae can be quite large. By not including post-event or post-exposure harm in environmental impact assessments, we miss much of the damage done by events like oil spills.”