World's Largest Dead Zone Suffocating Sea

James Owen in Stockholm for National Geographic News

A new danger to many marine species in Baltic Sea: An explosion of microscopic algae called phytoplankton has inundated the Baltic's sensitive waters, sucking up oxygen and choking aquatic life.

Image courtesy Jeff Schmaltz, NASA
 

Though a natural phenomenon at a smaller scale, these blooms have recently mushroomed at an alarming rate, fed by nutrients such as phosphorous and nitrogen from agricultural fertilizers and sewage. When it rains, farm fertilizers are washed into the sea. Sewage-treatment facilities also discharge waste into the Baltic ecosystem.

As a result, the Baltic is now home to seven of the of the world's ten largest marine "dead zones"—areas where the sea's oxygen has been used up by seabed bacteria that decompose the raining mass of dead algae.

Overfishing Adding to Algal Blooms

Overfishing of Baltic cod has greatly intensified the problem, Westman said. Cod eat sprats, a small, herring-like species that eat microscopic marine creatures called zooplankton that in turn eat the algae.

Too Late to Save the Baltic Sea?

Back in Stockholm, it's World Water Week, the annual global meeting on water issues organized by the Stockholm International Water Institute. On a conference room wall is a satellite image of the Baltic Sea, its deep blue edges giving way to a swirling, milky center that shows the algal blooms.

World Water Week attendees are pushing a new action plan called the Baltic Sea Strategy. The European Union-led initiative will attempt to coordinate the efforts of the eight EU members within the nine Baltic states—not including Russia—to revitalize their shared sea.

While the speakers all agree "it’s time for action," they don’t sound optimistic.

"It might well be too late," said Søren Nors Nielsen of the University of Copenhagen...

The whole article is published in National Geographic News and you can read it here.