Eutrophication

What is eutrophication?

Eutrophication - the process by which a body of water becomes enriched in dissolved nutrients that stimulate the growth of algae, resulting in the depletion of dissolved oxygen.

How does eutrophication reduce the dissolved oxygen in the body of water?

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Let’s look at Lake Atitlan in Guatemala

Sewage, agricultural runoff and deforestation all contribute to the swirls of blue-green algae that formed in Guatemala's Lake

Atitlán.

Let’s fly over to Namibia

Phytoplankton Bloom off Namibia: Off Namibia in November 2007 as a phytoplankton bloom grew and faded in the Atlantic Ocean. Such blooms are common in the coastal waters off southwest Africa where cold, nutrient-rich currents

sweep north from Antarctica and interact with the coastal shelf. At the same time, the easterly trade winds push surface water away from the shore, allowing water from the ocean's floor to rise to the surface, bringing with it iron and other

material.

Caused by upwelling in the ocean

Let’s fly over to the Barrents sea (where’s that?)

Algal Bloom in the Barents Sea:A coccolithophore is a tiny, surface-dwelling ocean plant that is coated with microscopic limestone (calcite) scales. This white coating makes the plant highly reflective. Coccolithophores flourish in nutrient-poor, sub-polar waters. Like other types of

microscopic ocean plants (phytoplankton), coccolithophores are an important food source for fish and other marine animals. Coccolithophore blooms occur when large numbers of the plants grow

in one place. Such blooms can be large: The visible portion of this bloom covers about 150,000 square kilometers (57,000 square miles) or roughly the area of Wisconsin.

Let’s go to the Black Sea!

In the spring of 2006, floods on the Danube River swept over broad stretches of farmland. The floods washed sediment, fertilizers, and animal waste into the Danube and the Black Sea. The extra iron, phosphates, and nitrates in the flood debris may be

supporting the extensive bloom seen here. Such blooms can be both beneficial, because they provide food for fish, and dangerous, because decaying plant matter

saps oxygen out of the water.

Is anybody up for a trip to Lake Ontario?

Anybody want to roll over to the Caspian Sea?

The Volga River is Europe’s longest river, flowing some 2,300 miles from northwest Russia to the Caspian Sea. As it winds its way through Russia, it passes through several

large cities, and it is lined with agriculture. The river picks up agricultural and industrial run-off, and these chemicals are deposited into the Caspian at the Volga

River delta.

Florida also has problems with eutrophication dead zones

Chesapeake Bay

Where was this picture taken? October 2000

November 2004