On November 19 1969, CSS Hudson It slipped through the frigid waters of the port of Halifax in Nova Scotia and out into the open ocean. The research ship was embarking on what many marine scientists on board believe is the last great and uncharted ocean voyage: the first complete voyage around the Americas. The ship was bound for Rio de Janeiro, where it would pick up more scientists before passing through Cape Horn – the southernmost point in the Americas – and then heading north across the Pacific to traverse the ice-packed Northern Passage to the port of Halifax.
Along the way , Hudson He stopped frequently so the scientists could collect samples and take measurements. One of those scientists, Ray Sheldon, had boarded Hudson in Valparaiso, Chile. A marine ecologist at Canada’s Bedford Institution of Oceanography, Sheldon was fascinated by the microscopic plankton that seemed to be ubiquitous in the ocean: How spread and vast are these microorganisms? To find out the answer, Sheldon and his colleagues moved buckets of seawater to the top HudsonIn the lab he used a plankton counting machine to count the size and number of organisms they found.
They discovered that life in the ocean follows a simple mathematical rule: the abundance of an organism is closely related to its body size. In other words, the smaller an organism is, the more of it it will find in the ocean. Krill is a billion times smaller than tuna, for example, but it’s also a billion times more abundant.
What is even more surprising is how accurately this rule is implemented. When Sheldon and his colleagues organized their plankton samples in order of size, they found that each arc contained exactly the same mass of organisms. In a bucket of seawater, one third of the mass of plankton would be between 1 and 10 μm, another third would be between 10 and 100 μm, and the last third would be between 100 μm and 1 μm. Each time they moved to a large-sized group, the number of individuals in that group decreased by a factor of 10. The total mass remained the same, while the population size changed.
Sheldon believed that this rule might govern all life in the ocean, from the smallest bacteria to the largest whales. It turns out that this intuition was correct. Sheldon’s spectrum, as it became known, is observed in plankton, fish, and freshwater ecosystems as well. (In fact, a Russian zoologist noticed the same pattern in soil three decades before Sheldon, but his discovery was mostly unnoticed.) “This suggests that no size is better than any other,” says Eric Galbraith, professor of Earth and planetary sciences at McGill University in Montreal. “Everyone has the same size of cells. And basically, for a cell, it doesn’t really matter what size of the body you live in, you tend to do the same thing.”
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