29 July 2010

Plankton in trouble?

Ingrid Sinclair
Copepod, a common form of zooplankton. Photo courtesy Anauxite

With all the focus on giant this and giant that, we tend to forget nature’s microscopic members and the comparatively massive role that they play in keeping everything in working order. Our aquatic animal health expert, David Vaughan, would agree that the tiniest creatures often pose the biggest threat when, for example, a parasite takes hold in an exhibit. But in certain cases, the littlest beings also form the basis for the Earth’s food chain – as is the case with plankton.

Massive aquatic animals like whales and whale sharks feed primarily on plankton, which is the collective term for microscopic plants (phytoplankton) and microscopic animals (zooplankton) that mostly live in the upper layers of the ocean and drift in currents to give life wherever they go. Plankton are also “the initial prey item for almost all fish larvae as they switch from their yolk sacs to external feeding,” according to Wikipedia.com.

Like all plants, phytoplankton photosynthesise by absorbing carbon dioxide and producing oxygen – more oxygen than all the forests in the world combined! Plankton plays a pivotal role on two levels, then, as a source of food and of oxygen. 

But a worrying statistic has surfaced: BBC News is reporting that “the amount of phytoplankton in the top layers of the oceans” has declined at about “1% per year” over the last century. Marine scientists have linked this decline to global warming and associated rising water temperatures, according to the International SeaKeepers Society. The society also reports that, “In some areas of the ocean, there has been a 30% decrease in phytoplankton production between 1999 and 2004 alone.”

While 1% might seem as tiny as plankton itself, the figure’s significance is large.

The continued existence of life is enmeshed in a very sensitive cycle and, just as warmer waters are threatening plankton populations, decreased concentrations of plankton in turn contribute to global warming, as less carbon dioxide (a greenhouse gas) is absorbed during photosynthesis.

Reversing global warming might seem like an impossible task, but an important one nevertheless. According to Discover magazine, the continued rise of sea temperatures “could rearrange the global distribution of life in the ocean and destabilise their food webs at their very root.”

All the more reason to act responsibly and help cool the planet, or at the very least try to slow down the alarming rate of global warming.

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