Gulf of Mexico Hypoxia and Mississippi River Basin Nutrient Losses. Herb Buxton, USGS. Rob Magnien, NOAA. Co-Chairs, Monitoring, Modeling, and Research Workgroup, Mississippi River/Gulf of Mexico Watershed Nutrient Task Force. What Causes Gulf Hypoxia?.
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Herb Buxton, USGS
Rob Magnien, NOAA
Monitoring, Modeling, and Research Workgroup, Mississippi River/Gulf of Mexico Watershed Nutrient Task Force
What Causes Gulf Hypoxia? Losses
“Hypoxia in the Northern Gulf of Mexico is caused primarily by excess N delivered by the MARB in combination with stratification of Gulf Waters.”– Integrated Assessment, 2000
Area of Hypoxic Zone
NOAA, Rabalais et al.
NITRATE LOAD, ANNUAL STREAMFLOW AND N CONCENTRATION
1955-70 Avg. = 350,000 t/yr 1980-99 Avg. = 950,000 t/y
Nitrogen Cycling Losses
Millions of Acres
CENR Science Assessment Losses
Task Force Action Plan,
Area of Hypoxic Zone
Action Plan Goals
Reducing Point Sources and Urban Runoff
Riparian Forest Buffers
Farm N Management
Diversions to Coastal Wetlands
Lock & Dam Management
1.6M metric tons per year
USGS Gaging Station
1500 Water-Quality Measurements
on 9 large sub-basins.
Nitrogen Yield, Losses
Yield on 42 small Sub-basins calculated from >4000 additional water-quality measurements.
N Input From Wet Deposition Losses
N Input From Fertilizer
N Input From Point Sources
Statistical extrapolation from representative basins (from 42 measured Sub-basins to 133 Sub-basins of entire Mississippi Basin).
Model Estimation of Total Nitrogen Delivered to the Gulf of Mexico(SPARROW)
A - Municipal and Industrial Discharges
B - Atmospheric Deposition , and
C - Fertilizer and Livestock Wastes.
6% +/- 3
18% +/- 10
Alexander et al. Nature, 2000
A Science Strategy to Support Management Decisions Related to Hypoxia in the Northern Gulf of Mexico and Excess Nutrients in the Mississippi River Basin
Available on the Internet:
What are the major sources and causes of excess nutrients within the Mississippi River Basin?
Nested scales to address and integrate processes from landscape to Basin-Gulf interrelationships.
BASIN MONITORING: Level 1 Losses
USGS Gaging Station Losses
BASIN MONITORING: Level 2
BASIN MONITORING: Level 3 Losses
BASIN MONITORING: Level 4 Losses
Next Step: LossesAction Plan: short-term action 11
By December 2005, and every 5 years thereafter, the Task Force will assess the nutrient load reductions achieved and the response of the hypoxic zone, water quality throughout the Basin, and economic and social effects. Based on this assessment, the TF will determine appropriate actions to continue to implement this strategy or, if necessary, revise the strategy.
Info On the Internet Losses
USGS Hypoxia in the Gulf of Mexico: http://toxics.usgs.gov/hypoxia/
USEPA Hypoxia Task Force:
NOAA Science Assessment: