Blue Ocean Institute

F02-1

Dead Zones

Dead zones are the result of runoff into the sea from land based activities, and they harm crabs, shellfish, and other sea life.

The creation of dead zones begins when nitrogen and phosphorus from fertilizers used on land, and from raw or poorly treated sewage, wash into streams, into rivers, and to the sea.  Thus fertilized, single celled drifting algae in the sea reproduce – bloom — until they reach abnormal densities.

The algae subsequently die and fall to the ocean floor, where they spark an explosion of bacteria that decompose them.  The bacteria deplete the oxygen in the sea water to levels so low that little else can survive.  Thus, a dead zone is created.

Fish can sometimes swim away from these dead zones, or algae blooms, but other sea life like clams and crabs cannot.

Since the 1970s, the number of dead zones has gone from a very few to hundreds around the world.  In 2008, there were 405 documented cases of coastal dead zones globally.

 

3 things you can do to help shrink dead zones:

1. Consider using organic compost or other natural fertilizers instead of commercial products on your lawn and garden
2. Buy locally grown food to support small-scale, regional farmers.
3. Get involved in local efforts to reduce commercial fertilizer use.

Other great ways you can make a difference.

LINKS & VIDEOS

Marine Pollution – World Wildlife Fund
Yearbook 2010 – United Nations Environmental Program

World’s Largest Dead Zone in Baltic Sea - National Geographic
NOAA Science: Dead Zones – You Tube


Related Videos:

Dr. Nancy Rabalais

The rise of global dead zones.


Dead zones, from fertilizer, cause fish die-offs.