In the arc of human history, it is only very recently that we have begun to live in a connected world. Long before Facebook and Twitter, human populations were separated by continents — and oceans — in ways that limited cultural and information exchange. It turns out the oceans are much more connected. This was brought home this week in a new scientific publication – and subsequent blog by my colleague Carl Safina – that unequivocally showed that Pacific bluefin tuna had transported radiation from the March 2011 Fukushima Dai-ichi nuclear power plant meltdown in Japan to the shores of California.

For many, this news will beg the question: “Should I avoid eating bluefin tuna?” The answer is unequivocally, “yes,” but not because of the radiation – which is at levels low enough that it won’t have an effect on humans – but because of sustainability. The Monterey Bay Aquarium rates bluefin as “avoid” because because they are being caught faster than they can reproduce. Attention sushi lovers: Bluefin is also known as hon maguro or toro (tuna belly). If you see it on the menu, and you care about the future of fish, you should avoid it. If conservation concerns don’t motivate you, the high price alone may steer you away.
Bluefin tuna are amazing creatures. Unlike most fish, bluefin are warm blooded. Using a heat exchanger much like the radiator in your car, they can elevate their body temperature as much as 20 degrees Celsius above that of the water in which they live. And boy can they swim; at a full sprint, bluefin can reach speeds of up to 30 miles per hour. The result? Bluefin can cover vast distances, regularly migrating between the western Pacific, near Japan, to the west coast of California.

When the Fukushima plant began to spill radioactivity into the ocean last year, I wondered whether that radioactivity might make it to our shores. Certainly, the Pacific is a very big ocean and even high concentrations of radioactivity would be expected to be diluted in its vast waters. But fish, like Pacific bluefin, also can accumulate radioactivity in their muscle tissues, and juvenile bluefin in the vicinity of the plant would be expected to pick up radioactive cesium (whose only source in the Pacific was the damaged plant). Indeed, when scientists sampled fish off the California coast, they found telltale signs of this cesium; they also determined that these fish had made the passage across the entire ocean basin in a matter of 4 months. While you and I can now do it on a jetliner in a few hours, this is a quick journey for a fish.

Pacific Bluefin – and other creatures like salmon sharks, sooty shearwaters, and loggerhead turtles – reveal just how connected the oceans are. They all make vast migrations, highlighting that there really is no “away” when it comes to the oceans. And marine life isn’t the only example driving this home. Much of west coast is poised for the arrival of vast amounts of trash from the Japanese earthquake, inexorably making its way here, pushed by the wind and waves. My colleague, Nick Mallos is part of an expedition right now studying and tracking the tsunami debris. You can learn more about the expedition through his blog posts and twitter account.

While our smartphones connect us to friends and family, it is the bluefin tuna that really show how connected life on “planet ocean” really is.