Terrebonne

Bay

L.Calcasieu Atchafalaya R

M ississippi R 

L.

50 km

3.5

92.5 89.5 9 1.5 90.5

– Distribution of frequenc y of occurrence of m id- sum m er h y poxia —

 from R abalais, Turner and W isem an from the 60 to 80 station g rid

m pled from 1985-1999

Hypoxia

Frequency of Occurrence

1985 - 1999

Lon g itude
1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

Histogram of estimated areal extent of bottom water hypoxia for mid

1985-99 --- based on data from N. Rabalais, Louisiana Universities Marine

Areal Extent of Hypoxic Zone 1985 - 1999

no data
trophication Process” (modified from Downing et al. 1999) – Eutrophication occurs when organic matter increases in

hication can lead to hypoxia when decaying organic matter on the bottom depletes oxygen and replenishment is blocked

lux of organic matter to the bottom is fueled by nutrients carried by riverflow or, possibly, from upwelling that stimulate

on algae. This flux consists of dead algal cells together with fecal pellets from grazing zooplankton. Organic carbon

contribute to the flux of organic matter.
FIGURE 2.2 – Long-term records of Gulf ecosystem changes - Include organic carbon profile (#1 fig 70 - 1

profile (station 10), without terrestrial/marine breakout); biogenic silica profile (#1 fig 69 - 1 profile from

E30), and glauconite and ostracod profiles (both from #1 fig 72)

Biogenic Silica

Glauconite

Ostracod

Organic Carbon Accumulation Rate (mgC/cm2/yr)

0.00

0.40

0.80

1.20

1.60

1900 1915 1930 1945 1960 1975 1990

0.0

5.0

10.0

15.0

20.0

25.0

1900 1915 1930 1945 1960 1975 1990

0

0.25

0 .5

0.75

1

1.25

1 .5

1900 1915 1930 1945 1960 1975 1990

0.0

2.0

4.0

6.0

8.0

10.0

1900 1915 1930 1945 1960 1975 1990
0

8000000

1900 1920 1940 1960 1980 2000

 Long-term records of drainage basin changes - annual amount of fertilizer

d area artificially drained (see #5 figure 1.2 and #3 page 44 for details)

642

Estimated nitrogen fertilizer usein the Mississippi River Basin

Estimated land drainage inMississippi River basin states

tons per year millions of acres

8

0

2 04 06 08 0

1900 1920 1940 1960 1980 2000
Annual loads of nitrate, organic nitrogen and annual streamflow from the

er Basin to the Gulf of Mexico 1955-98

streamflow

Organic N

nitrate

1960 1990 1965 1995 2000 1970 1975 1980 1985

Mississippi River Streamflow in

thousands of cubic meters per second

1510

5

202530
5A – Annual Nitrogen Inputs to the Mississippi/Atchafalaya River Basin

1950 1960 1970 1980 1990 2000

0

1

2354678

Year
B – Annual Nitrogen Outputs to the Mississippi/Atchafalaya River Basin
– Annual Nitrogen Inputs, Outputs and Residuals (inputs minus outputs)

n Mass Balance for 1951-96

residual

outputs

inputs

0 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

01

23

4

Year

Residuals (Nitrogen Inputs Minus Outputs)

in Million Metric Tons per Year
1980 1985 2000 1990 1995

GURE 2.7 – Flux of Nitrate from the Mississippi River Basin to

 Gulf of Mexico 1980 to August-1999

2468

0

0
Average annual nitrate yields (1980-96) for 42 basins within the Mississippi

er Basin
rends in annual shrimp yield recorded by the National Marine Fisheries Service

d Texas, 1979 - 1998 -- The lines include 3-year moving averages. The data are

w.sf.nmfs.gov/st1/commercial/landings/index.html)

1980 1985 1990 1995

Brown ShrimpWhite ShrimpAll Shrimp
Cumulative residual (nitrogen inputs minus outputs) from nitrogen mass

MARB (from #3, Figure 6.4B)

50 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

1955

cumulative residuals (excluding Nitrogen output in Mississippi River discharge) cumulative residuals (including Nitrogen output in Mississippi River discharge)
NUTRIENTS LOADING

PRODUCTION AND FISHERY YIELD

OLIGO-TROPHIC MESO - EU - DYS -

BENTHOS

BENTHOS -

FEEDING

FISH

ZOOPLANKTONTIVOROUS

FISH

OTHER ZOOPLANKTON

FEEDERS

(e.g. MEDUSAE)

SEASONAL BOTTOM ANOXIA

PERMANENT

SE North Sea

N. Gulf of Mexico

N. Adriatic Sea

Great Lakes

Kattegat

Baltic Sea

Seto Inland Sea

Yellow Sea

NW Black Sea

Chesapeake Bay

Oligotrophic Mesotrophic Eutrophic Dystrophic ?

Comparative Evaluation of Fishery Ecosystems

Response to Increasing Nutrient Loading

?

Figure 4.2 - Comparative evaluation of fishery response to nutrients (redrawn from Caddy,

1993) -- Each curve represents a species guild and their reaction to increasing nutrient

supplies. The figure’s top half list recent trends for systems world-wide. Vertical dashed

lines separate categories of organic production which result from different nutrient levels.
le of forested riparian buffers in trapping nutrients before entering stream

Zone 3 Zone 2 Zone 1

Runoff Control Managed Forest Undisturbed

Forest

Stream Bottom
2 - The role of riparian wetlands in capturing nutrients during flood events
 -- Adaptive Management Feedback Loop — connecting the following 4 steps

process:

 Monitor System Response; Data Interpretation, Model Analysis and Improvement; Model Prediction and Management Plan Improvement; Implement Management Strategy