Ch.3 Case Study

Name ______________________________ Class ________ Date _________ by Savvas Learning Company LLC. All Rights Reserved. 1 Central Case The Gulf of Mexico’s Dead Zone The Changing Size of the Dead Zone The hypoxic zone, or area of low oxygen, in the Gulf of Mexico varies in size from year to year. The National Oceanic and Atmospheric Administration (NOAA) supports research that measures and monitors the size of the dead zone in the Gulf of Mexico annually. The graph below shows the results of such research. This data help scientists determine which factors cause the dead zone to grow or shrink. Most analyses show that the biggest factor in the size of the dead zone is the amount of nitrogen and other nutrients that reaches the Gulf from the Mississippi River watershed each spring. The U.S. Geological Survey (USGS) measures the amount of nitrogen that reaches the Gulf each year and correlates that amount with the size of the dead zone. Its scientists have found that when the amount of nitrogen increases, the size of the dead zone increases. Currently there are several plans to reduce the size of the dead zone to an acceptable level, indicated by the Action Plan Goal line on the graph. Although the dead zone is fueled by nitrogen runoff, scientists know that short-term weather patterns can also have an effect on the size of the hypoxic region. For example, when the region experiences periods of extreme weather, the heavy winds and wave activity cause more oxygen to infuse into the waters—counteracting the effects of nitrogen runoff and slowing the growth of the dead zone. Scientists feel it is important to track and account for these short-term effects, in the model they are developing to study the dead zone as well. This way, they will be able to establish a link between fertilizer runoff and size of the dead zone without having the data skewed due to weather effects. Establishing a good model with all the data available can help achieve the goals needed to reach acceptable levels. With the dead zone reduced in size, the Gulf of Mexico can then be restored for fishing and recreation. Area of Dead Zone, 1985–2007 Dea d Zone Area (sq mi) 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 1985 1986 1987 Long-Term Average Action Plan Goal Year *1988: value of data too small to appear *1989: no data available Data from N.N. Rabalais, Louisiana Universities Marine Consortium. Funded by NOAA, Center for Sponsored Coastal Ocean Research.