Dumping in the Ocean

As stated before, overfishing is wiping out our oceans. We're also doing particularly nasty things like dumping chemical weapons, mercury, and nuclear reactors into the ocean. Things are not good when pregnant women can't eat fish due to high levels of mercury:

While the hadal zone is almost entirely unexplored, it is not untouched, for humans have been bombarding it with an array of materials ranging from deadly toxins to entire ships. The number of vessels lost to the deep during wars is well known, but what is more surprising is the number lost in peacetime. According to Lloyd's register, an average of one ship was lost at sea every two days between 1971 and 1990, and a great many go down with their cargoes and polluting fuel oil aboard. Yet these are some of the mildest threats to the abyss. Until 1972 it was a common practice to dump unwanted munitions at sea, including chemical weapons. Britain alone has dumped 137,000 tons of unwanted chemical weapons at sea, and some of the chemicals still remain in solid form on the bottom.

Following 1946 a far more ominous kind of waste began to be dumped—radioactive material. Until the practice was banned in 1993, 142,000 tons of such waste had been dumped in the North Atlantic alone. Secrecy makes it difficult to know the full extent of the problem, but in 1993 it was revealed that the Russians had illicitly dumped seventeen entire nuclear reactors into the Arctic Sea. Some marine creatures concentrate radioactive elements in their bodies. The liver-like glands of one species of shrimp, for example, have levels of polonium-210 a million times that of seawater, which makes scientists worry about the consequences of this deadly dumping.

Other pollutants include industrial waste and sewage, compounds that, among other effects, cause sex changes in mollusks, as well as chlorinated hydrocarbons (the villains of Rachel Carson's Silent Spring), mercury (most of which comes from burning coal on land, and provides the reason why pregnant women should abstain from fish), and cadmium, which can destroy organs in humans. As Tony Koslow piquantly reminds us, "neither distance nor depth shields the deep sea from pollution." Rather, our pollutants rain down from the sky and sea surface in a relentless stream, and like the sump of an engine, the deep is where much of the muck accumulates. But unlike a sump, the pollutants of the deep don't stay there. Instead they find their way back to us in the fish we eat.

Link (via Bradford Plummer)