Gulf of Mexico Dead Zone

Topic(s):

No topics assigned.

Scenario:

Background Information:

The Gulf of Mexico is a large ocean basin located within the Atlantic Ocean. Like the Mediterranean Sea, it is a partially land-locked intercontinental marginal sea. The Gulf encompasses about 600,000 square miles, and provides critical marine resources for the commercial and sport fisheries of U.S., Mexico and Cuba, all of which border the Gulf of Mexico.

Thirty-one agriculturally rich states and two Canadian provinces drain into the Mississippi River and its tributaries, which in turn drains into the Gulf of Mexico. These water bodies carry a sediment load and run-off from agricultural activity, and the fertilizers carried into the Gulf creates eutrophic conditions in the coastal waters between Mississippi and Texas. Seasonally, increased nutrient influx into the Gulf creates an imbalance in the aquatic ecosystem, resulting in oxygen depletion, or hypoxia, known as the "Gulf of Mexico Dead Zone." The Dead Zone appeared seasonally for decades, but there is growing concern about the extent and severity of the phenomenon. Since 1985, when the Dead Zone was first carefully studied, it has roughly doubled in size. In summer, 2008, the Dead Zone's area was roughly the size of the state of New Jersey.

As global warming and eutrophication reduce oxygenation of the world ocean, there is a pressing need to understand the functional consequences of oxygen depletion in marine ecosystems. Marine dead zones occur worldwide: the Baltic Sea, Black Sea, off the coast of Oregon, and in the Chesapeake Bay. They can even be found in lakes, such as Lake Erie. The Gulf of Mexico dead zone is one of the largest in the world. Unlike Oxygen Minimum Zones (OMZs) that are sustained at depths where the rate of oxygen consumption by bacteria degrading organic matter exceeds oxygen production, dead zones are a downstream effect- the result of too many nutrients entering a watershed. The hypoxia tends to go away after October as cooler weather slows algae growth and storms mix the water.

Tasking:

The second largest man-made dead zone in the world's coastal waters is found in the Northern Gulf of Mexico. In 2008, the dead zone was estimated to cover 20,720 sq km, an area about the size of New Jersey.

State and federal agencies have set a 2015 deadline for reducing the dead zone to a quarter of its historic size. However, a recent report by the National Research Council is urging more rapid action to resolve the issue. Part of the problem is that no single agency is responsible for addressing the dead zone issue, and "piecemeal" approaches have been ineffective. The report urges the USDA and the EPA to form a water quality center for the entire river basin that can evaluate the various efforts that are being made to reduce nutrient loads into the Mississippi.

Your group has been tasked with studying and reporting on mitigating strategies that will reduce the dead zone. Examples might include expanding sustainable agriculture, reducing concentrated-animal feeding operation (CAFOs), or limiting the type of fertilizers farmers can use.

Date: 2/16/2009

Scenario Images:

MODIS/Aqua satellite image of highly turbid water of the Mississippi Delta entering the Gulf of Mexico. The red and orange colors in the image represent high concentrations of phytoplankton and river sediment (image courtesy of NASA)

The Mississippi River drainage system carries nitrogen loads to the Gulf of Mexico, which fuels population explosions in phytoplankton. The Mississippi drains 31 states and 2 Canadian provinces: all runoff from agricultural fields in this region ultimately ends up in the Gulf (image courtesy of USDA)

Gulf of Mexico Dead Zone: a clearly demarcated interface between the blue, oxygenated waters and the oxygen-poor (hypoxic) brown zone (photo courtesy of NOAA)

A key player in the Gulf of Mexico Dead Zone is phytoplankton: single-celled, photosynthetic organisms that serve as the basis of the ocean's sun-based food web. Summer rains wash nutrients into water systems that feed into the Mississippi River and ultimately, the Gulf of Mexico. The nutrients fuel large phytoplankton blooms, greatly icreasing the amount of organic matter which sinks to the bottom and is decomposed by bacteria. In the process of breaking down the organic matter, the bacteria consume oxygen and release carbon dioxide, decreasing the availability of dissolved oxygen for fish and other sea creatures. The balance of the food web is greatly disrupted. (Photo credit: NASA)

The GCOOS Data Portal provides timely/real-time environmental data from the buoy network about the Gulf of Mexico and its estuaries. Real-time buoy data are available and landscape visualizations are enhanced from Google Earth.

Resources:

On Again, Off Again: The Dead Zone (Cycle A)
the Louisiana Sea Grant College Program has assembled a number of websites related to Gulf of Mexico hypoxia.

The Dead Zone and a Minnesota Farmer's Battle (Cycle A)
A Minnesota farmer says the Gulf fishermen are his neighbors. He has changed the manner in which he operates his farm in order to lessen the impact on the Gulf's dead zone.

The Way We Eat is Trashing the Fragile Conditions that Make Human Life Possible (Cycle A)
This short article provides an introduction to one of the sources of the hypoxia problems in the Gulf of Mexico, and will help you get started.

What makes the Gulf of Mexico Dead Zone "Dead"? (Cycle A)
This interactive resource designed for elementary and middle school students, It includes digital resources for self exploration, a self-administered quiz and sample laboratory experiments to explore physical and biological principles associated with the Gulf of Mexico Dead Zone. This resource is in English and Spanish

Hypoxia in the Northern Gulf of Mexico (Cycle B)
This website contains background information for the instructor, powerpoints, data, and a guide for instructing students in mapping the areal extent of hypoxia using data from the 1993 cruise.

Microbial Life Educational Resources: The Gulf of Mexico Dead Zone (Cycle B)
This link provides a comprehensive collection of resources for both students and teachers. the Dead Zone-Advanced Collection provides primary resources that allows the phenomenon of hypoxia to be examined in greater detail.

Gulf of Mexico Coastal Ocean Observing System Data Portal (Cycle C)
The Data Portal provides information about the Gulf of Mexico, including visualizations supported by Google Earth. The interactive map allows users to examine real-time buoy data.

Gulf of Mexico Hypoxia Watch Data and Products (NOAA) (Cycle C)
The objective of Hypoxia Watch is to develop new near-real time data and map products using shipboard measurements of bottom dissolved oxygen and to disseminate the data over the Internet. Go to "Data and Products" on the navigation bar to access data from the 2009 cruise.

Sample Investigations:

The Feeding Frenzy: Seasonal Upwelling (6-8) (Cycle A)
The goal of this teaching box is to teach students about the abiotic factors that drive the process of upwelling, and the biotic response to this physical phenomena. Students will deepen their understanding of the dynamics that create a seasonal abundance of marine life in coastal upwelling zones. Students will discover this process through exploring the following:

Density and wind-driven currents
Marine food webs
Primary food production in the ocean
Seasonal changes in abiotic factors and biotic resources
Difficulty: beginner

Water Quality Degradation in the Ocean (9-12) (Cycle A)
A BETA version lesson from National Geographic containing pre-readings, small group work, hypotheses investigations and leaning extensions.
Difficulty: beginner

A NOAA Estuarine Water Quality Unit (9-12) (Cycle B)
This unit on water quality is from the NOAA NODE project that makes use of data in the classroom. Students study dissolved oxygen, salinity, spawning of Atlantic Sturgeon then design their own investigation using real data.
Difficulty: beginner

Bringing Coastal Dead Zones Back to Life (Cycle B)
Why are the Waters Dying examines the impact of nutrient pollution, and provides a lesson plan and resource links. Students examine the issue of Dead Zones and engage in analysis of the contribution of their community to coastal water quality issues downstream.
Difficulty: intermediate

What is Responsible for Smaller Shrimp Catches? (Cycle C)
This interactive website provides an exploratory environment for students to learn more about the causes and effects of the Dead Zone. Summary questions are provided throughout the resource for learning evaluation.
Difficulty: intermediate

Standards:

• Science
  National Science Education Standards - Science Content Standards http://www.nap.edu/readingroom/books/nses/html/overview.html#content The science content standards outline what students should know, understand, and be able to do in the natural sciences over the course of K-12 education.
  • GRADES 9-12 CONTENT STANDARDS
    • Science as Inquiry (Std A)
      • Abilities necessary to do scientific inquiry
      • Understanding about scientific inquiry
    • Earth and Space Science (Std D)
      • Energy in the earth system
      • Geochemical cycles
    • Science in Personal and Social Perspectives (Std F)
      • Personal health
      • Personal and community health
      • Population growth
      • Natural resources
      • Environmental quality
      • Natural and human-induced hazards
      • Science and technology in local, national, and global challenges