1. Nancy N. Rabalais et al. Ocean Deoxygenation and Coastal Hypoxia
in a Changing World”
GESAMP 39
18 April 2012
Nancy N. Rabalais et al.
Louisiana Universities Marine Consortium

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

3. Nutrient Yields from the Mississippi Basin
Alexander et al &

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

5. Extensive, Severe Low Oxygen Waters Source: N. Rabalais, LUMCON
up to 22,000 km2
4 - 5 m nearshore to 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
2011
2010
maximum
average
minimum
Mississippi River Discharge Hydrographs
Tarbert Landing, MS ( )
Cubic feet per second x 1000 *
Trans C&F
Shelfwide
Heterosigma bloom

9. Heterosigma akashiwo
Station: C6C, approx 15 miles south of LUMCON (29o N / 90 o 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: mg/L

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

11. Distribution of bottom-water dissolved oxygen LA TX MS AL
Mississippi River
Atchafalaya River
Distribution of bottom-water dissolved oxygen
July (east of the Mississippi River delta) and
July (west of the Mississippi River delta), 2011.
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.

12. June 18, 2011 rain

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

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

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