Saturday, August 16, 2008

pig food

We encountered lots of algae on Petenwell Lake while vacationing in central Wisconsin this summer. The guy who handled our boat rental had just come from a meeting in which people whose livelihoods depend on the health of the lake were pitted against the powerful agricultural commmunity, source of much harmful runoff.

The sea of green reminded us of China's problems with the same. An account in the International Herald Tribune summarizes:
Olympic nightmare: A red tide in the Yellow Sea

By Jim Yardley
Published: June 30, 2008

source: IHT, caption: Residents clearing the coastline of Qingdao, Shandong province on Monday. (Stringer/Reuters)


Many coastal Chinese cities dump untreated sewage into the sea. At the same time, rivers and tributaries emptying into coastal waters are often contaminated with high levels of nitrates from agricultural and industrial runoff. These nitrates contribute to the red tides of algae that often bloom along sections of China's coastline.

But officials in Qingdao said pollution and poor water quality did not have a "substantial link" to the current outbreak. Instead, scientists blamed the bloom on increased rainfall and warmer waters in the Yellow Sea. Algae are now blooming over more than 12,900 square kilometers, or 5,000 square miles, of the sea, according to Xinhua.

State media reported that 100,000 tons of the algae had already been taken out of the water. Much of it was being transported to farms as feed for pigs and other animals, according to news reports.
Today, there's an AFP report on the problem:

Ocean 'dead zones' expanding worldwide: study
by Virginie Montet Fri Aug 15, 4:33 PM ET


"The formation of dead zones has been exacerbated by the increase in (pollution) ... fueled by riverine runoff of fertilizers and the burning of fossil fuels," the study said.

The phenomenon, called eutrophication, is caused by industrial pollution as well as runoff of water containing phosphates and nitrates into the oceans.

Oceans react to the boost in pollution by growing more algae and vegetation in coastal areas.

When the algae dies and sinks to the bottom, it decreases the amount of oxygen available in the bottom waters, a process called hypoxia, eventually wiping out fish and crustaceans that live there, as well as the foods they eat.

Dead zones tend to creep up in calm waters that see lower water exchange, but have more recently been affecting major fishery areas in the Baltic, Kattegat, and Black Seas as well as the Gulf of Mexico and East China Sea, the study said.

The researchers said the expansion of dead zones in these areas threatens commercial fishing and shrimping near the coastlines.

The phenomenon was first noted along the Adriatic Coast in the 1950s.

Seasonal dead zones affect the Gulf of Mexico, Chesapeake Bay and Scandinavian waters.
Here are some photos I took on Lake Petenwell:

The lake is clear at its north end, where the Wisconsin River flows into it.

At that point, you can fish, swim, and idle an afternoon away drifting on clear waters.

On the eastern shore things are very different. The surface is green.

In protected areas of the eastern shore, like the marina where we rented the boat, the problem is acute. The smell is ugly.

The surface is so deeply green that in places it's blue.

And lies thick enough on the surface to support a cast-off soda bottle.

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