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Aquatic Organic Carbon and Nutrient Fluxes, Water Quality,
and Aquatic Productivity in the Atchafalaya Basin, Louisiana 1
Victor W. Lambou 2
Abstract.--Aquatic carbon and nutrient fluxes, water
quality, and productivity in the Atchafalaya Basin, Louisiana
are reviewed" Overflow areas had large areal net exports of
nitrogen and dissolved organic carbon but acted as a sink for
phosphorus. Ammonia levels increased dramatically during the
summer. Primary production in the overflow areas was primarily above the water surface and energy chains within the
water are basically dependent upon heterotrophic production.
INTRODUCTION
isolated by levees. Of most value from a
fisheries and recreational standpoint is the
Atchafalaya Basin Floodway, which during normal
years has in excess of 1,619 km 2 flooded by
overflow from the Atchafalaya River.
The Atchafalaya Basin contains one of the
largest remaining floodplain bottomland hardwood
forests in the United States and supports major
sport and commercial fisheries and outdoor recreational uses dependent upon the annual flooding of
the forest (Lambou 1985). This paper reviews
aquatic carbon and nutrient fluxes, water quality,
and productivity in the Basin.
Water normally enters the Basin from two
major sources. A portion of the Mississippi
River's flow enters through the Old River Control
structures and eventually joins with the Red
River to form the main stem of the Atchafalaya
River. The main stem flows are then confined by
levees until the river enters the Atchafalaya
Basin Floodway. There the water spreads out
through distributaries and during high water by
overbank flows over almost the entire Atchafalaya
Basin Floodway. The water exits through ~he Wax
Lake and Lower Atchafalaya River outlets.
DESCRIPTION OF AREA
The Atchafalaya Basin (fig. 1) comprises an
8,345 km 2 lowland floodplain area confined between
natural levee ridges that delineate the present
and former courses of the Mississippi River. Its
overall dimensions are approximately 72 by 193 km
with elevations ranging from 15 m to sea level.
There are six segments in the Atchafalaya
Basin which have integrity due to manmade levee
systems. These are: (1) the 287 km 2 Morganza
Floodway, (2) the 611 km 2 West Atchafalaya Floodway,
(3) the 340 km 2 Pointe Coupee Sump Area, (4) the
2,129 km 2 Atchafalaya Basin Floodway--historically
subject to fre uent and prolonged natural flooding,
(5) the 259 km leveed Atchafalaya River and
other segments located mainly between the upper
Atchafalaya River and levees and Old River, and
(6) the 4,719 km 2 East and West Basin areas
1
1presented at The First North American
Riparian Conference, Riparian Ecosystems and their
Management: Reconciling Conflicting Uses, Tucson,
Arizona, April 16-18, 1985.
2Victor W. Lambou is with the Environmental
Monitoring Systems Laboratory, United States
Environmental Protection Agency, Las Vegas, Nevada.
180
The Atchafalaya River receives approximately
30% of the combined flows of the Mississippi and
Red Rivers at the latitude of the Old River
Control structures. Atchafalaya River discharges
show both seasonal and annual variation. The
"average shifted hydrograph" for the Atchafalaya
River at Simmespart indicates the seasonality of
flows (fig. 2). The hydrograph was computed from
daily discharges at the latitude of Old River and
adjusted to 30 percent of the total flow to
account for the presence of the Old River structure~.
Each year's hydrograph was shifted to peak on
April 15 (the day the unshifted average hydrograph
peaked) before averaging, since daily averages of
unshifted hydrographs result in considerably
lower peak stages than is representative of
actual conditions.
The cyclic nature of the flows shown in
figure 2 also describes the typical annual regime
of overflow for the Atchafalaya Basin Floodway.
The other segments of the Basin are not subjected
to the same type of prolonged overbank flooding.
Figure 1.--The Atchafalaya Basin, Louisiana.
points within the Atchafalaya Basin Floodway.
Helicopters were employed to collect water and
biological samples on 14 separate occasions from
1974-77 at which time 80 to 130 stations throughout
the Basin were sampled in approximately 10 days.
Intensive sampling of five areas (Fordoche,
Buffalo Cove, Pat Bay, inlet of the Basin proper,
Atchafalaya River main stem, and the outlets of
the Basin proper - Wax Lake and Morgan City) was
conducted using small boat crews on approximately
a monthly basis.
12
10
~
u
8
0
6
~
E
0
4
100
2
M
A
M
A
S
0
N
0
Figure 2.--Average daily shifted hydrograph for
the Atchafalaya River at Simmesport,
Louisiana, for the period 1947-48, adopted
from U.S. Army Corps of Engineers (1982).
Detailed comparisons are made in this report
for three distinct hydrological subunits within
the Basin. Two of these, Fordoche and Buffalo
Cove, are part of the Atchafalaya Basin Floodway
and show seasonal water-level patterns that mimic
those of the Atchafalaya River. The Fordoche
subunit receives some local runoff from outside
the leveed Atchafalaya system which is not true
of other hydrological subunits within the
Atchafalaya Basin Floodway. The third subunit,
Pat Bay, is isolated from the historical influence
of the river by manmade levees. Water-level
patterns in this unit are now determined exclusively
by local runoff. Hydrological patterns of the
three subunits studied are compared in table 1.
MATERIALS AND METHODS
A total of 148 sampling stations were located
throughout the Atchafalaya Basin. Locations
included the major inlet and outlets to the
Atchafalaya Basin Floodway and major water exchange
181
Integrated samples for chlorophyll a (CHLA)
and organic carbon were collected by pumping.
CHLA samples were integrated from the lower limit
of the photic zone to the surface while carbon
samples were integrated from top to bottom.
Samples for total phosphorus (TP), dissolved
orthophosphate (OP), nitrite-nitrate nitrogen
(N02N03N), ammonia (NH3N), total kjeldahl
nitrogen (KJEL), dissolved oxygen (DO), total
alkalinity (TALK), and pH were collected at
selected depths to represent the water column.
In extremely shallow water or in fast moving main
channel areas, samples were collected only from
the surface. In a previous study, it was
determined that in fast flowing waters in main
channel areas physical and chemical constituents
are uniformly mixed (U.S. DI 1969). Samples
were collected on a total of 1,301 station-day
combinations. The sampling methods and design
are more fully described by Hern et ale (1980).
Analyses were performed in acccordance with
the procedures described in EPA (1971, 1974) except
for chlorophyll a and water transparency. Chlorophyll a analyses-were performed according to the
fluoro;etric procedure described by Yentsch and
Menzel (1963) and corrected for pheophytin while
water transparency was measured in the field by
Secchi disk readings. Total organic carbon (TOC)
Table 1.--Comparison of three hydrological subunits within the Atchafalaya Basin
Hydrological subunit (area)
Period
flooded (months)
Buf f a 10 Cove
Within
Atchafalaya
Basin Floodway
(91 km 2 )
0- 1
1- 4
4- 8
8-11
11-12
3
9
47
17
15
Fordoche
Within
Atchafalaya
Bas in F loodway
(270 km 2 )
0- 1
1- 4
4- 8
8-11
11-12
97
20
56
20
77
Pat Bay
Outside
Atchafa1aya
Basin F100dway
(45 km 2 )
0- 1
1- 4
4- 8
8-11
11-12
24
5
9
4
3
Area
flooded (km 2 )
Area
flooded (%)
Average maximum depth
of flooding (m)
Type of flooding
<0.1
0.4
0.8
1.1
>1.1
Overbank flooding:
a) headwater to backwater; h) active
exchange of water between overbank areas, permanent water
bodies and major channels.
7
21
7
29
<0.1
0.4
0.8
1.0
>1.0
Overbank flooding:
a) backwater to headwater; b) active
exchange of water between overbank areas, permanent water
bodies and major channels.
54
12
19
8
7
<0.1
0.0
0.2
0.4
>0.4
Flooding associated with local precipitation events: a)
flooding generally short-lived and involves relatively
small percent of the area; b) shallow "rainwater swamps"
created with flooding periods highly variable ranging
from 1 to 11 months; c) minor water exchange between
"rainwater swamps" and permanent water bodies; d) water
loss from "rainwater swamps" largely by evapotranspiration.
10
52
19
16
36
was determined from unfiltered samples while
dissolved organic carbon (DOC) and dissolved
nutrients were determined from samples filtered
through type HA 0.45-micron Millipore filters.
Particulate organic carbon (POC) was determined by
subtraction. Total nitrogen (TN), organic nitrogen
(ON), and inorganic nitrogen (ION) were determined
by addition or subtraction as follows: KJEL +
N02N03N, KJEL - NH3N, and NH3N + N02N03N, respectively. See Hern et ale (1980) for more details.
In order to determine ambient parameter means,
calculations were performed in such a way to give
equal weight to each depth sampled at a station on
a particular day, each day sampled at a station
during a time interval, and each station sampled
in a given geographical area during a time interval. If a parameter was not sampled on at least
three different days during i time interval, the
station was not used in determining the mean
value for the time interval. The ratio of TP to
ION (Nip) was determined only when data points
for TP, NH3N, and N02N03N values were all available. Seasons were defined as follows: winter,
December 21-March 20; spring, March 21-June 20;
summer, June 21-September 20; and fall, September
21-December 20. High water was defined as any
time flows in the Atchafalaya River at Simmesport
were> 4,799 m3 ·s- 1 (the mean discharge for a 9-year
period, 1963-1971) and low water as any time flows
were < 4,799 m3 ·s- 1 .
Using topograhic data from U.S. Army Corps of
Engineers and U.S. Geological Survey maps, a
storage curve was developed for the Fordoche,
Buffalo Cove, and Pat Bay hydrological subunits.
These curves relate water-level changes at key
gauging stations to the net volume of water added
or released from the subunit during a given time
interval. Time intervals over which net storage
changes were determined extended over one or more
days during which water-level changes were in a
single direction. Storage changes due to precipitation and evapotranspiration were determined by
using daily precipitation values from the nearest
U.S. weather station and average monthly evapotranspiration rates as obtained through water
balance calculations from long-term records (19451968) at those stations. The remaining part of
the storage change then represented the net
change in water volume as a result of inflow,
182
outflow, or a combination of the two. Annual net
inflow and outflow volumes determined for the
period July 1, 1976 through June, 1977 are:
Buffalo Cove
Fordoche
Pat Bay
254
1,179
57
267
1,348
79
These volumes were then proportioned to the various water exchange points within the Fordoche or
Buffalo Cove subunit. For the Pat Bay subunit,
intermittent discharge measurements over the
period did not allow for apportioning of outflow
or inflows and did not suggest simultaneous
occurrence of inflow or outflow.
This subunit
was therefore treated as a single inlet-outlet
system in which net storage change due to the
flow was equated to actual inflow or outflow.
Carbon fluxes were determined by mUltiplying
carbon concentration times flow volumes at each
major opening of the various hydrological subunits
for the period July 1, 1976 through June, ~977.
Carbon and nutrient fluxes for the Atchafalaya
Basin Floodway were determined by using published
daily flow records for the Atchafalaya River (U.S.
GS 1976, 1977). As flow data were only available
for the inlet to the Floodway (115,060 10 6m3 for
the period July 1, 1976 through June, 1977), it
was assumed that all water entering the system
must exit through the two outlets. This is
reasonable considering the fact that changes in
volume due to precipitation and evapotranspiration
are negligible compared to the volume of water
(fig. 2) entering and leaving the system. The
inflow water was proportioned to 60 percent
exiting through the Lower Atchafalaya River outlet and 40 percent through the Wax Lake outlet,
based on data collected by the U.S. Corps of
Engineers. Fluxes were determined by multiplying
concentrations times flow volumes during the
period July 1, 1976 through June, 1977. A measured
concentration on a particular sampling day was
assumed to be representative of the concentration
in the inflow or outflow for a period of time
halfway back to the previously and forward to the
next measured concentration.
RESULTS AND DISCUSSION
Carbon and nutrient fluxes are presented in
table 2. Even though the entire leveed Atchafalaya
Basin drains directly or indirectly through the
Atchafalaya Basin Floodway, I feel it is inappropriate to use the Basin's total area to calculate
or determine areal net export for the Atchafalaya
Basin Floodway. The processes which control
internal input to the system, as well as deposition
and conversion, take place mainly within the area
subject to overflow, and this area is totally
within the Atchafalaya Basin Floodway.
Fundamental differences exist in carbon
fluxes between those areas which are subject to
extensive overflow (Atchafalaya Basin Floodway,
Buffalo Cove, and Fordoche) as compared to the
non-overflow subunit (Pat Bay). The overflow
areas had large annual areal net exports of DOC
while the non-overflow subunit had a relatively
low areal net export. Areal export of POC was
high in the non-overflow subunit while the overflow areas acted as sinks for POCo Weighted mean
DOC concentrations in the outflow of the overflow
areas increased over the concentrations in their
inflow. There were some differences in carbon
fluxes between the Atchafalaya Basin Floodway as
a whole and its two overflow subunits which were
sampled. The Atchafalaya Basin Floodway acted as
a sink for TOC mainly through the loss of POCo
Quantities of POC decreased by 35 percent in its
outflow over that in its inflow, while quantities
of POC decreased by only 17 percent and 16 percent
in the outflow of its two overflow subunits. Net
export of DOC was very similar for all three
areas.
The greater deposition rate of POC in the
Atchafalaya Basin Floodway can be explained by
historical changes in sedimentation patterns and
water flows. Flows from the Mississippi River
began to be diverted on a regular basis to the
Atchafalaya River in the mid-1900s (Fisk 1952).
Diversion steadily increased until 1963 when the
Old River Control structures (fig. 1) were placed
into operation in order to prevent the complete
capture of the Mississippi River by the Atchafalaya
River. The deposition of sediments associated
with the increase flows have almost eliminated
Grand and Six Mile lakes which originally occupied
a significant portion of what is now the Atchafalaya
Basin Floodway (Fisk 1952, Roberts et al. 1980).
Presently, the main area for sedimentation is
rapidly changing to the Bay area below Morgan
City. However, significant amounts of sediments
are still being deposited in remanent lakes and
backswamp areas as well as on developing natural
levees in the lower portion of the Atchafalaya
Basin Floodway. I believe that as part of this
process, large quantities of POC are being deposited
causing the Basin to act as a sink for TOC and,
Table 2.--Annual nutrient and organic carbon fluxes for the
Atchafalaya Basin Floodway and organic carbon fluxes
for Buffalo Cove, Fordoche, and Pat Bay
Import
Weighted
mean (mg· 1 -1 )
Gross Export
Weighted
kg·l0 3
mean (mg·l- 1 )
Net
export
kg .10 3
Ratio of
net export
to import
(%)
Aeral net
export
(kg·km- 2 )
Atchafalaya Basin
1Fl oo dway (2,129 km 2 )
-20
-103,116
9.73
899,827
7.82
-219,534
1,119,361
TOC
11,172
4.01
23,785
5
3.80
461,383
437,598
DOC
-36
-114,288
5.93
438,443
-243,319
3.81
681,762
POC
-23
-3,438
-7,319
0.28
24,427
0.21TP
31,746
1,517
29
713
0.04
6,672
0.06+
5,155
OP
18
11 ,050
23,526
1.16
157,260
1.37+
TN
133,734
1,999
33
0.11
0.15+
4,256
12,713
16,969
NH3N
7
5,122
2,406
0.67+
76,914
0.62
71,792
N02N03N
8,644
0.70+
18,404
30
0.54
80,346
61,942
KJEL
29
6,645
14,148
0.55+
63,378
0.43
49,230
ON
4,405
9,378
11
0.73
93,882
0.82+
84,504
ION
Buffalo Cove (91 km 2 )
33
708
7,776
2,881
10.78
8.56
TOC
2,173
148
10,650
969
2.57
1,621
6.06
DOC
652
-17
-261
-2,873
1,260
4.71
5.99
POC
1 522
Fordoche (270 km 2)
17
2,225
8,240
11. 67
11.46
15,738
TOC
13,513
44
3,142
11,636
7.63
6.06
10,286
7,145
DOC
-14
-3,396
-916
5.40
4.04
5,452
POC
6,369
Pat Bay (45 km 2 )
698
12.08
1,126
14.21
427
61
9,490
TOC
439
7.58
488
6.61
50
11
1,105
DOC
POC
260
4.49
637
8.04
377
145
8,385
1If the area is considered to be the entire leveed Atchafalaya Basin (3,626 km 2 ) the areal
net export in kg·km- 2 for TOC, DOC, POC, TP, OP, TN, NH3N, N02N03N, KJEL, ON, and ION would be
-60,544; 6,560; -67,104 -2,018; 418; 6,488; 1,173; 1,413; 5,076; 3,902; and 2,586, respectively.
183
are given in table 3. Both TP and nitrogen
levels found in the Atchafalaya Basin are high.
NH3N levels dramatically increase during the
summer in the Atchafalaya Basin Floodway undoubtedly due to the mineralization of ON via ammonification. Nip ratios are relatively low in the
Atchafalaya Basin suggesting nitrogen limitation
for autotrophic production (Lambou et al. 1976).
However, both organic and inorganic forms of
nitrogen and phosphorus are biologically available
to bacteria. Complete metabolism (mineralization
of carbon) at optimal rates by bacteria requires
carbon:nitrogen:phosphorus ratios of approximately
100:10:1 to 100:5:1 dependent upon bacterial
community composition and environmental conditions (Alexander 1961). In addition, many of the
constituents of the total organic pool do not
undergo rapid breakdown and therefore do not
represent a significant drain upon the available
nitrogen pool. Herbaceous material and leaf
litter flooded during high water stages in the
Basin contain sufficient nitrogen to support
their breakdown by bacteria. Also, undoubtedly
nitrogen fixation is an important source of nitogen to the Atchafalaya Basin as evident by the
relatively large areal export of TN. Significant
fixation would be expected under the conditions of
fairly low Nip ratios that occur in the Atcha£alaya
Basin. Dierberg and Brezonik (1983) found that
nitrogen fixation was in important source of
nitrogen in natural cypress swamp domes in Florida.
when sediment deposition decreases sufficiently,
the Atchafalaya Rive~ will become a net exporter
of TOC to the estuarine area below Morgan City.
The Atchafalaya Basin Floodway had a large
areal net export of TN mostly in the form of ON
(table 2). Weighted mean concentrations increased
in the outflow over the concentrations in the
inflow for all forms of nitrogen. The Atchafalaya
Basin Floodway acted as a sink for TP, mainly in
the form of particulate phosphorus. The quantity
of OP increased by 29 percent in the outflow over
that in the inflow.
Taylor et al. (1984) has reviewed inputoutput nutrient studies in forested wetlands
reported in the literature. They found that for
all four studies reviewed, the wetlands acted as
sinks for TN. However, Mattraw and Elder (1984)
found that the overflow floodplain of the
Apalachicola River in Florida exported TN. The
outflow mass was 20 percent greater than that in
the inflow which is similar to the 18 percent for
Atchafalaya Basin Floodway. Taylor et al. found
that for eight studies, the forested wetlands
served as a sink for TP which is consistent with
the decrease of 23 percent found in the outflow
over that in the inflow of the Atchafalaya Basin
Floodway. However, Mattraw and Elder found 23
percent more TP in the outflow from the Apalachicola
River's floodplain. Undoubtedly the sedimentation
in the lower portion of the Atchafalaya Basin
Floodway discussed previously has had some effect
on nutrient export from the Atchafalaya Basin
Floodway.
CHLA levels outside the leveed Atchafalaya
Basin were much higher than those inside the leveed Atchafalaya Basin system (table 3) even
though nutrient levels were high in both areas.
The relatively lower SD readings within the
Ambient parameter means for selected geographic areas within the Atchafalaya Basin Floodway
Table 3.--Ambient parameter means for selected geographic
areas within the Atchafalaya Basin Louisiana
DOC
TOC
POC
TP
OP
NH3N
N02N03N
(mg' I-I ) (mg'I- 1 ) (mg' I-I) (~g'I-1 ) (~g'1-1 ) (~g'rl) (~g'r1)
1Leveed Atchafalaya
Basin System (79)
KJEL
DO
(~g '1- 1 ) (mg'I- 1 )
CHLA
(~g '1- 1 )
SD
(I")
pH
TALK
(mg '1- 1 )
Nip
10.2
6.3
4.7
194
63
126
229
768
5.8
8.5
19
7.3
92
3.2
Low water
9.1
10.3
9.0
9.9
7.3
8.3
9.7
5.5
7.2
5.9
4.4
4.0
4.6
6.2
4.3
3.7
4.0
5.4
4.0
3.8
4.9
176
178
219
170
123
244
173
53
60
71
36
31
80
40
118
90
57
309
61
75
186
349
334
403
294
309
390
266
697
594
674
941
596
703
893
6.0
7.2
4.7
5.6
7.7
5.2
6.2
8.4
3.5
5.0
16.4
9.5
7.4
14.3
20
28
19
18
18
26
18
7.3
7.3
7.2
7.5
7.4
7.2
7.4
93
77
80
104
109
78
103
3.8
3.6
3.0
5.6
3.3
2.4
4.0
Fordoche (16)
Winter
Spring
Summer
Fall
High water
Low water
12.1
16.2
12.2
12.7
9.7
12.8
12.3
8.3
12.0
10.0
6.4
4.6
10.0
7.7
4.8
5.7
4.0
6.7
5.1
3.9
6.2
219
215
251
275
159
288
242
77
89
110
56
44
90
66
140
85
112
369
120
121
226
169
93
198
190
156
293
143
934
856
850
1,351
899
787
1,145
4.9
5.5
3.6
3.6
6.4
4.6
4.4
9.2
2.8
9.3
13.9
13 .9
4.4
13.8
19
18
23
15
16
19
19
7.2
7.0
7.0
7.2
7.5
7.2
7.2
83
47
71
109
112
68
93
1.8
0.8
1.9
2.5
1.9
2.6
1.8
Buffalo Cove (16)
Winter
Spring
10.4
10.6
10.1
10.9
9.4
9.0
11.4
6.0
7.2
6.6
4.2
4.6
5.1
6.7
5.3
4.3
4.3
6.4
4.8
4.0
7.0
203
224
224
219
124
304
256
70
82
102
14
29
144
45
113
105
70
287
63
116
181
278
381
377
180
166
359
92
719
591
725
1,038
620
764
1,071
5.3
6.3
3.9
4.6
7.8
4.4
5.8
9.6
7.4
5.9
17.0
10.5
10.5
16.3
22
32
20
21
16
35
18
7.1
7.1
7.0
7.0
7.4
7.1
7.1
101
79
90
111
123
87
111
3.0
3.6
3.3
3.7
1.9
2.5
1.8
2Atchafalaya Basin Floodway (57)
Winter
Spring
Summer
Fall
High water
Summer
Fall
High water
Low water
Outs ide leveed Atchafalaya
System (37)
11.4
6.6
5.6
207
54
155
303
1288
7.2
15.0
13
7.8
89
2.5
Pat Bay (5)
Winter
Spring
Summer
Fall
12.4
11.3
13.8
11.7
8.2
8.0
8.3
9.4
6.4
4.1
5.2
3.6
5.5
6.6
4.2
187
151
236
224
114
68
46
98
73
35
157
57
59
237
268
119
84
146
101
130
857
723
866
1098
713
5.6
5.3
4.9
5.6
7.5
12.7
5.8
12.5
19.8
18.2
23
42
15
13
12
7.6
7.3
7.6
7.8
7.7
109
95
114
118
112
1.7
0.9
1.1
1.7
2.6
1Number of stations located within a geographic area is given in parentheses.
2Atchafa1aya Basin F100dway exclusive of the Fordoche area.
184
Atchafalaya Basin Floodway reflect higher mineral
turbidity levels.
Primary production within the overflow area
is primarily above the water surface and on dry
land during low water periods while energy chains
within the water are basically dependent upon
heterotrophic production. Hern and Lambou (1977)
found phytoplankton to be approximately five times
as high in Pat Bay (8,000 cells'ml- l ) as in
Buffalo Cove (1,800 cells'ml- l and Fordoche (1,500
cells·ml- l . Aquatic primary productivity estimates
based on oxygen production and carbon dioxide uptake were found to be in the order of two to five
times ~~ea~Ir in Pat Bay (11.1 02 and 26.8 C02
mmol'm 'h ) as c~mpa~ed to Buffalo Cove (5.2 O2
and 5.4 CO 2 mmol'm =;h
and Fordoche (7.5 O2
and 16.3 CO 2 mmol'm 'h ). Based on data presented by Hern and Lambou, aquatic production/
respiration ratios for Buffalo Cove and Fordoche
were 0.19 and 0.34, respectively, indicating an
heterotrophic system.
=1
Table 4.--Percent of the time DO concentrations
were below 2 and 4 mg'l- l by water level
and selected geographic area
Water Level
Season
Winter Spring Summer Fall Hi~h Low Total
117
312
164
481
106
194
64
2
13
4
11
39
29
11
26
22
25
35
38
19
26
67
51
118
8
21
5
13
9
11
22
50
47
11
38
25
33
29
~
21
46
88
66
154
0
22
4
6
11
10
11
0
58
61
10
34
39
36
8
9
The Atchafalaya Basin Floodway is extremely
productive of aquatic life, and finfish and
crawfish harvest rates of 8,797 km'km- 2 'yr- 1 per
maximum area flooded have been documented (Lambou
1985). The key to the high productivity of the
Atchafalaya Basin Floodway is the short, efficient, bacteria-detritus food chain (Lambou 1985).
Given sufficient nutrients (nitrogen and phosphorus) and adequate DO levels, carbon becomes
the lifeblood of the aquatic system. Prolonged
overbank flooding, with the inundation of additional land areas containing herbaceous material
and forest litter renew the carbon resources
needed to drive the bacteria-detritus system.
LITERATURE CITED
Dierberg, F. E., and P. L. Brezonik. 1983. Nitrogen and phosphorus mass balances in natural
and sewage-enriched cypress domes. Journal
of Applied Ecology 20:323-337.
Fisk, H. N. 1952. Geological investigations of
the Atchafalaya Basin and the problem of
Mississippi River diversion. U.S. Army
Corps of Engineers, Waterways Experiment
Station, Vicksburg, Miss. Vol. 10, 145 pp.
Hern, S. C" and V. W. Lambou. 1979. Productivity
responses to changes in hydrological regimes
in the Atchafalaya Basin, Louisiana. In:
Proc. Int. Symp. on Environmental Effects of
Hydraulic Engineering Works, pp. 93-102 Tenn.
Valley Authority, Knoxville, Tenn.
Hern, S. C., V. W. Lambou, and J. R. Butch. 1980.
Descriptive water quality for the Atchafalaya
Basin, Louisiana. EPA-600/4-80-014, Environmental Monitoring Series. 168 pp.
Lambou, V. W., L. R. Williams, S. C. Hern, R. W.
Thomas, and J. D. Bliss. 1976. Prediction of phytophlankton in lakes. In:
Proceedings of the Conference on Environmental Modeling and Simulation, EPA-600/
9-76-016. pp. 696-700.
Lambou, V. W. 1985. Importance of bottomland
hardwood forest zones to fish and fisheries:
the Atchafalaya Basin, a case history. To
be published in the Proceedings of Bottomlands. Hardwoods Workshops, St. Francesville,
La. 63 pp.
Mattraw, H. C., and J. F. Elder. 1984. Nutrient and
detritus transport in the Apalachicola River,
Florida. U.S. Geological Survey water supply paper 2196-C. 62 pp.
Roberts, H. H., R. D. Adams, and R. H. W. Cunningham.
1980. Evolution of sand-dominant subaerial
phase, Atchafalaya Delta, Louisiana. Am.
Ass. Petrol. Geol. Bull. 64:264-278.
DO levels within the Atchafalaya Basin
Floodway are sometimes relatively low because of
decomposition of litter in the flooded forests
(table 3). The mean DO saturation was only 61
percent inside the leveed Atchafalaya Basin system while outside the leveed system it was 80
percent. Insufficient DO in the water column can
cause fish kills and/or anaerobic decomposition
of organic material with concomitant releases of
ammonia and other noxious gases such as hydrogen
sulfide. However, before the onset of anaerobic
conditions DO levels became too low to provide
for the maintenance and well-being of the fish
population as a whole. DO levels of 2 and 4
mg'l- l were selected to compare conditions which
may be detrimental to fish populations (table 4).
These levels have been reported to impact growth
and development of fish or to produce lethal
1Atchafalaya Basin
Floodway
No_ of days
measured
Percent of
time (2 mg-I- 1
Percent of
time (4 mg-I- 1
Buffalo Cove
No_ of days
measured
Percent of
time (2 mg-I- 1
Percent of
time (4 mg-I-1
Fordoche
No- of days
measured
Percent of
time (2 mg-I- 1
Percent of
time (4 mg-I- 1
conditions even though finfish and crawfish have
been found in DO levels as low as 1 mg'1- 1 in the
Fordoche area (Lambou 1985). The majority of the
low DO problems occurred in the spring.
Taylor, J. R., M. A. Cardamone, and W. J. Mitsch.
1984. Bottomland hardwood forests, their
functions and values. Mitsch and Associates. Louisiana, Ky. 87pp.
1Atchafalaya Basin Floodway exclusive of Fordoche_
185
u.s.
u. S. Department of the lnte rior.
u.s.
u.s.
1969. Endrin
pollution in the Lower Mississippi River
Basin. Federal Water Pollution Control
Administration, Dallas, Tex.
213 pp.
Environmental Protection Agency.
1971.
Methods for chemical analysis of water
and wastes. Analytical Quality Control
Laboratory, Cincinnati, Ohio.
312 pp.
Environmental Protection Agency.
1974.
Methods for chemical analysis of water
and wastes.
National Environmental
Research Center, Cincinnati, Ohio.
298 pp.
Geological Survey.
1976. Water resources
data for Louisiana water year 1976. U.S.
Geological Survey Water-Data Report LA-76-1.
463 pp.
u.s. Geological Survey. 1977. Water resources
data for Louisiana water year 1977. U.S.
Geological Survey Water-Data Report LA-771.
405 pp.
Yentsch, C. S., and D. W. Menzel. 1963. A method
for the determination of phytoplankton
chlorophyll and phaeophytin by fluorescence.
Deep Sea Res.
10:221-231.
186