Dead Zones
Tyler Jaynes
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What are dead zones?
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Hypoxic (low-oxygen) areas in the World oceans, lakes, reservoirs.
o Can’t support aquatic life.
 Support obligate aerobic life?
o Size can range from a few meters to the largest of 70,000 square kilometers.
What are the causes of dead zones?
o Human activity: Farming
 Fertilizer runoff from farms
o Eutrophication: increase chemical nutrients in the water. (phosphorus and nitrogen)
 Freshwater from the Mississippi River flows on top of saltwater.
 Keeping oxygen from the atmosphere reaching deeper water.
o Decomposition of dead organism. (fish and other aquatic life)
o Flow of raw sewage in poorly developed countries.
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What are the effects of dead zones in World’s oceans, lakes, reservoirs?
o Decrease size of reproductive organs
 Lowering the number of eggs
 Limiting spawning activity
o Suffocation of fish and other sea organism.
 Leads to death
o Increase in algal bloom
 Spurring the growth of algae.
 Zooplankton eats the algae, excreting pellets that sink to the bottom like
tiny stones.
What solutions can be done to stop Dead Zones?
o Use safer alternatives for fertilizer.
 Using organic fertilizer that is water-soluble and slow-release.
 Planting clover or any other legumes that fix nitrogen into the soil from
nodules on their roots.
o Monitor the amount of fertilizer is being used.
o Crop rotation
Scavia, Justic, and Beirman, Jr. “Reducing hypoxia zone in the Gulf of Mexico: Advice
three models.” 2004. Estuaries. Vol. 27. Pg. 419-425.
Reducing Hypoxia in the Gulf of Mexico: Advice from Three Models.
o Goal: To understand how to reduce hypoxia in the Gulf of Mexico.
o Methods: Use three models
 model conceptual framework
 model calibration
 conceptual model of oxygen
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Results: Large hypoxic dead zones were not likely to have occurred prior to the
mid 1970s, that the size of those regions grew a maximum in the 1980s and then
fluctuated between the mid-1980s and present. (Justic et al. 2002)
References
Raunekk. 2009. “How are dead zones created in the Sea?”
Achenbach, Joel. 2008. “A 'Dead Zone' in the Gulf of Mexico”. The Washington Post. Vol.1 Pg.
A02.
What is the Gulf of Mexico Dead Zone? Science Museum of Minnesota.
http://www.smm.org/deadzone/top.html
Flicker, John. 2009. Watershed/Runoff: Alternatives to Fertilizers and Pesticides. Pathways to
The three R’s. University of Maryland. Vol. 1. Pg 1.
Bierman.Jr. V. Justic, D. Scavia, D. 2004. Reducing Hypoxia in the Gulf Mexico: Advice from
Three Models. Estuaries. Vol. 27. No.3. Pg 419-425.