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Ocean Deoxygenation and Coastal Hypoxia i n a Changing World ”

This paper discusses the issue of ocean deoxygenation and coastal hypoxia, examining its causes and consequences in a changing world. It explores the impacts of anthropogenic activities, climate variability, and nutrient loads on hypoxic areas, as well as the biological and physical responses to these changes. The paper also highlights the importance of monitoring and predicting hypoxia to mitigate its effects.

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Ocean Deoxygenation and Coastal Hypoxia i n a Changing World ”

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  1. Ocean Deoxygenation and Coastal Hypoxia in a Changing World” GESAMP 39 18 April 2012 Nancy N. Rabalais et al. Louisiana Universities Marine Consortium nrabalais@lumcon.edu http://www.gulfhypoxia.net

  2. Goolsby et al. 1999, Rabalais 2002 Point Source 10% Nonpoint Source 90%

  3. Nutrient Yields from the Mississippi Basin Alexander et al. 2008 & http://water.usgs.gov/nawqa/sparrow/gulf_findings/

  4. Mississippi River – Gulf of Mexico Ecosystem Continuum Hypoxic Area Mississippi River Atchafalaya River New Orleans Effects are more far reaching than suspended sediment plume, esp. N & somewhat P dominant wind direction Source: N. Rabalais

  5. Extensive, Severe Low Oxygen Waters Source: N. Rabalais, LUMCON • up to 22,000 km2 • 4 - 5 m nearshore to 35 - 45 m offshore • 0.5 km nearshore to 100+ km offshore • widespread and severe in Jun – Sep

  6. April 29 rain June 18 rain

  7. Mississippi River Discharge Hydrographs Tarbert Landing, MS (1930-2011) Trans C&F Shelfwide Heterosigma bloom * 2011 2010 maximum Cubic feet per second x 1000 average minimum *

  8. Heterosigmaakashiwo Station: C6C, approx 15 miles south of LUMCON (29o 52.12 N / 90 o 29.42 W) Date: March 21, 2011 Bottom Depth: 19.5 m Bloom Color: Greenish-brown Salinity: 28.7 psu Chlorophyll: 117 ug/L Oxygen: 204% oxygen saturation DO: 16-17 mg/L

  9. Predicting Hypoxia in summer (nitrate-N flux in May, year) Turner et al. 2006

  10. Distribution of bottom-water dissolved oxygen July 18-21 (east of the Mississippi River delta) and July 24-30 (west of the Mississippi River delta), 2011. Mississippi River LA TX LA MS AL Atchafalaya River Data source: NN Rabalais, Louisiana Universities Marine Consortium, and RE Turner, Louisiana State University. Funding source: National Oceanic and Atmospheric Administration, Center for Sponsored Coastal Ocean Research. http://www.gulfhypoxia.net

  11. June 18, 2011 rain

  12. Anthropogenic activities Climate variability climate change Sea level rise (+) Water temperature (mostly +) Winds Reactive N (mostly +) Hydrologic cycle (+) (-) Nutrient loads (+) (-) Biological responses (Metabolic rates mostly +) (Primary production +) (Respiration +) Physical environment (Stratification +) (Oxygen saturation -) (Current shifts) (Tropical storms) Nutrient-enhanced productivity Harmful & noxious algal blooms Vertical carbon flux Bottom-water hypoxia Sedimentary carbon and nutrient pools Rabalais et al. 2009, 2010

  13. 7,000 120 Symptoms of Eutrophication  6,000 100 5,000 80 4,000 60 3,000 40 2,000 20 1,000 0 0 1800 1850 1900 1950 2000 2050 Humans, millions Fertilizer, Tg N Legumes/Rice, Tg N NOx emissions, Tg N They are increasing Developed Countries Developing Countries (modified by N. Rabalais;Galloway and Cowling 2002; Boesch 2002)

  14. The Future Climate Change Biofuels Increased Population Increased Agribusiness Increased Atmospheric Deposition

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