Earth’s Oceans

A fascinating article in the Economist asks, What would we see if we could see through the sea? A few highlights:

On plankton: “The world’s stock of phytoplankton, tiny photosynthetic algae and bacteria. Its total mass is far less than that of the plants that provide photosynthesis on land, but every year it takes 50 billion tonnes of carbon out of the atmosphere, turning it into organic matter for the ocean’s inhabitants to eat. Scant though the planktonic biomass is, it does roughly as much biogeochemical work as all the continents’ forests, savannahs and farms.”

One of the most surprising things about the oceans is that they are largely empty: “Simon Jennings of CEFAS, a research centre in Lowestoft, in England, and Kate Collingridge have made a brave stab at estimating how many fish there are in the sea by applying ecological modelling. Their result is strikingly small: 5 billion tonnes of fish weighing between a gram and a tonne. If piled together, those fish would not even fill Loch Ness, which though an impressive body of water is nugatory compared with the whole ocean. Even if Dr Jennings is off by a factor of ten, the volume of fish would still be less than that of Lake Geneva. Broadly, the world boasts less than a minnow for every Olympic swimming pool of its seawater. Yet life in the ocean can still mount sublime spectacles.” That says less about the number of fish than about the unfathomable vastness of the oceans.

And on human passage over the seas: “more than 111,000 ships hanging as if suspended in empty space, according to estimates of the size of the world’s merchant fleet from IHS. They are the workplaces, and sometimes homes, of at least 1.5m seafarers, and more than 500 liners provide temporary accommodation to hundreds of thousands of passengers, too. This disassembled city of steel carries some 90% of all international trade by weight. Its wandering buildings can carry, between them, over 1 billion tonnes of cargo: a mass equivalent to one cubic kilometre of water, a little less than a billionth of the total volume of the ocean.”