Baltic Sea Now Home To 7 Of 10 Of Planet's Largest Marine Dead Zones - Nat Geo

[hatrack]

EDIT

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. "We’ve had enormous algal blooms here the last few years which have affected the whole ecosystem," Westman said.

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. So, fewer cod and an explosion of zooplankton-eating sprats means more algae and less oxygen.

This vicious cycle gets worse as the spreading dead zones engulf the cod’s deep-water breeding grounds, he added.

The algal blooms, which can be toxic to animals and human swimmers, leave behind an ugly layer of green scum that fouls tourist beaches and starves seaweeds of light. "Other species have taken the place , which don’t provide as good habitats for fish," especially juveniles, Westman said. "In the past couple of years common fishes like pike and perch have had virtually no reproduction in the inner part of the archipelago." This vicious circle gets worse as the spreading dead zones engulf the cod’s breeding grounds.

EDIT

http://news.nationalgeographic.com/news/2010/02/100305-baltic-sea-algae-dead-zones-water/

[kestrel91316]

1. Eat the sprats!!!! They are edible, IIRC.

[The Croquist]

2. I would have guessed that China would be up there but it doesn't look like it

I guess that they're pretty light on the use of fertilizer but I can't imagine that they treat their sewage much.