Saturday, October 14, 2006

Science Matters: Ocean life makes waves

In this week's Science Matters column, David Suzuki writes about the interconnectedness of everything on our planet, and a tiny action in one part of the world can have larger effects across the other side. Thus, we are all like the butterflies, and need to be mindful of what happens when we 'flap our wings'...

Ocean life makes waves

Most people have heard of the “butterfly effect” – the idea that a small change, such as a butterfly flapping its wings in one part of the world, can set in motion a series of events that leads to a big event, such as a tornado, somewhere else. The term is largely used as a metaphor, but science now shows that there’s a literal aspect to the theory that has much broader implications.

To say that everything is connected to everything else has become a cliché, but it’s true – especially in nature. Scientist and author James Lovelock uses the term “Gaia” to describe the Earth as a living, self-regulating system. According to this hypothesis, all of the planet’s biological creatures are intimately connected with all of its physical systems, from the soils to the oceans to the atmosphere. Changes in any of these systems can affect everything else.

We can see how connected everything is when we release long-lasting substances into the atmosphere. Toxins, for example, can drift out of a smokestack in Hamilton, Ontario or Mumbai, India, circle the earth on the winds or ocean currents, and end up in seemingly pristine areas such as the Far North. In fact these toxins are now found concentrated in the fat of marine mammals and in human breast milk.

In an interconnected world, even a creature as small and seemingly inconsequential as the tiny, shrimp-like krill can have a big impact. These one-to-two centimeter-long creatures already play an important role in the ocean food chain and are a staple in the diet of some of the world’s largest whales. But krill are so small that few would have suspected they could play an important role in generating currents that help mix our ocean waters.

Yet, that’s exactly what a team of researchers from the University of Victoria found off the coast of British Columbia’s Vancouver Island. The researchers looked at a deep ocean inlet where different layers of the water mix very little. They found that thousands of krill, on their nightly upward migration from the deep water to the surface to feed, increased the mixing of water by three to four orders of magnitude. In other words, these tiny creatures actually cause quite a stir.

And it isn’t just krill that cause this water stirring, or “turbulence.” All living organisms that exhibit similar behaviour can cause turbulence, helping to bring cold, nutrient-rich water up to the surface. This exchange of cold and warm water is vital to the productivity of the oceans. It also helps break down human wastes and it even plays an important role in the climate.

But turbulence has largely been thought to be driven almost exclusively by physical forces, like the winds and the tides, rather than by biological forces. The very idea that the behaviour of individual organisms can affect entire systems seems fantastic. Yet the researchers in Victoria conclude that sea creatures themselves may be a critical, but overlooked, source of turbulence in the oceans.

Other researchers go ever further. An article in the Journal of Marine Research calculates that, based on the math, swimming organisms may be one of the most important drivers of ocean turbulence. If this is the case, the authors conclude, then the overfishing that has caused fish stocks to plummet, and the near extinction of many whale species due to hunting may have disrupted ocean turbulence enough to have affected the planet’s climate.

Seemingly small actions can have big consequences. More and more, we are finding that our world is not nearly as vast and limitless as we once supposed. Not only is it interconnected, but it is this very interconnectedness that drives it. In this world, we are all butterflies and we need to be mindful of what can happen when we flap our wings.

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