1. KATLYND REESE AQUATIC ECOLOGY 9 NOVEMBER 2011 Hypoxia or “Dead Zones” in Aquatic Systems

2. Outline Introduction and background information Some effects of hypoxia Examples  Lake Erie  The Gulf of Mexico Causes Prevention Recent article

3. What is Hypoxia? Hypoxia is defined as a condition where the DO is less than 2-3 ppm Often referred to as a “dead zone” in a body of water A complete lack of oxygen is referred to as “anoxic” http://www.edupic.net/fish.htm

4. Background Information Dead zones have always existed historically Currently appearing in shallow coastal and estuarine waters Dead zones are being found in larger and larger areas of water Lasting for a longer time

5. Effects of Hypoxia Kills sedentary animals Severely decreases animal and plant diversity Habitat loss Weakening or loss of populations Significant loss in coastal regions with high natural diversity

6. Examples of Harmful Dead Zones The Gulf of Mexico Lake Erie http://www.scientificamerican.com/article.cfm?id=oceanic-dead-zones-spread

7. Examples: Gulf of Mexico http://www.greendiary.com/entry/dead-zone-in-the-gulf-of-mexico/

8. Examples: Gulf of Mexico Occurs where the Mississippi River meets the Gulf Water stratifies due to salinity differences  Epilimnion: fresh water is less dense  Hypolimnion: salt water is more dense  Crates stratification Results in anoxic conditions in more dense waters Nutrient loading into the Mississippi is another possible cause A high biodiversity area

9. Examples: Lake Erie http://www.noaanews.noaa.gov/stories2005/s2427.htm

10. Examples: Lake Erie Central Basin Sever eutrophication Stratification  Before fall mixing…  Warm epilimnion and cold hypolimnion  Shallow central basin cannot hold very much oxygen Not only affects ecosystem but also the fishing industry and therefore economy

11. Causes of Hypoxia http://water.epa.gov/type/watersheds/named/msbasin/hypoxia101.cfm

12. Causes of Hypoxia Algal blooms and nutrient loading  When large amounts of algae die they sink to bottom  Decomposition uses up a lot of DO Abiotic conditions of body of water  Depth and shape  Wind and weather  Flow strength and direction Global Warming  Temperature increase can decrease the maximum amount of DO  Exacerbates the eutrophication problem

13. Prevention Reduce use of fertilizers and manage their use Practice clean boating Preserve land adjoining rivers and streams http://www.dbw.ca.gov/Pubs/CleanBoatingHabits/Default.aspx

14. Recent Article: Diaz and Rosenberg “Spreading dead zones and consequences for marine ecosystems” Diaz and Rosenberg in Science 2008 Recorded the growth of dead zones across the planet Found over 400 hypoxic zones in the world Tracked energy flow and community maturity to determine health of the aquatic ecosystems

15. References Diaz, Robert J. et al. 2008. “Spreading dead zones and consequences for marine ecosystems”. Science 321: 926. http://water.epa.gov/type/watersheds/named/msba sin/hypoxia101.cfm http://www.eoearth.org/article/Hypoxia_fact_sheet http://toxics.usgs.gov/hypoxia/hypoxic_zone.html http://www.esa.org/education/edupdfs/hypoxia.pdf http://water.epa.gov/type/watersheds/named/msba sin/upload/diaz_article.pdf