A deadly poison created by mixing sunlight and oil in shallow water

While a huge body of research has been done on the immense oil spill in the Gulf Coast, another, smaller, spill in the San Francisco Bay has shown not only that we don't know much about how different types of oil behave in the environment — but also that they can interact in ways we didn't predict.

In 2007, the ship Cosco Busan spilled bunker oil — a combination of diesel and residual fuel oil — into the San Francisco Bay, contaminating herring-spawning habitats. While in the deeper water, the herrings were hit with the expected heart defects resulting from non-lethal petroleum doses — problems which exist in their population to this day — but where the water was less than one meter deep, there was a major spike in deaths.

The bunker oil had a number of unidentified components to it — and one of these chemicals interacted with the sunlight in the shallow water, becoming rapidly more toxic. This, in turn, caused the eggshells to rupture spontaneously (like in the picture above). So even if a bunker oil spill has a much lower volume than a crude oil spill, it can have a much higher impact — and shallow water, with sunlight reacting with the oil, can make matters much worse.