us army corps of engineers building strong ® the effects of suspended sediment from western lake...
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US Army Corps of Engineers
BUILDING STRONG®
The Effects of Suspended Sediment from Western Lake Erie on Walleye (Sander vitreus) Eggs and Fingerlings?Burton Suedel, C.H. Lutz, J.U. Clarke, D.G. Clarke
USACE-ERDC-EL, Vicksburg, MS
C. Godard-Codding and J. Maul
The Institute of Environmentaland Human HealthTexas Tech UniversityLubbock, TX
Dredging 2012San Diego, CA24 October 2012
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Sediment Resuspension
The most frequently cited concern related to restrictions imposed on dredging schedules
Exposures may affect: Spawning or foraging behavior Egg hatching success and larval development Disrupt anadromous fish migrations Physical disturbance of habitat by increased
sedimentation rates
Engbretson Underwater Photography
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Setting Environmental Windows is Controversial
EW: Time periods that allow dredging No consistent, broadly accepted methodology
for objectively setting EWs has emerged Often set without scientific basis Established by negotiations emphasizing
conservative professional judgments Lack of effects data for suspended sediments
on species used to set EW
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Maumee Bay Study Area
SpawningArea
LarvalNursery
Area
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Near-field Plume ConditionsMaumee Bay Study Area
0
100
200
300
400
500
600
700
9:4
8
9:5
5
10
:02
10
:09
10
:16
10
:23
10
:30
10
:37
10
:44
10
:51
10
:58
11:0
5
11:1
2
11:1
9
11:2
6
11:3
3
11:4
0
11:4
7
11:5
4
12
:01
12
:08
12
:15
12
:22
12
:29
12
:36
Time
NT
U (
mg/
L)
Near-field (2.2 m Depth) Near-field (7.0 m Depth) Ambient (7.0 m Depth)
46 m 30 m
15 m LWC Max. Turb. 700 NTU (15 m) < 300 NTU (30m)
Max. TSS 800 mg/l
Plume Width 50 m
Distance from Dredge: 3m
Entrained Air
UWC Max. Turb. 175 NTU (15 m) 50 NTU (30m) Ambient in < 50 m
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Materials and Methods
Flow-through Fish Larvae and Egg Exposure System (FLEES)
3 modules/3 500 L water baths/15 aquaria
Aquaria (15) constructed from 20 L polyethylene carboys
Pump recirculated water and suspended sediment in aquaria
Sediment mixed with water and stored in 375 L tank via double diaphragm pump
Slurry routed through FLEES and reused
Sediment concentrations monitored using OBS
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Materials and Methods
Walleye (Sander vitreus) Four experiments:
northern and southern strain eggs (newly spawned) and fingerlings (45-60 d old)
Sediment: Maumee Bay, Ohio (Lake Erie)
Concentrations: 0, 100, 250, 500 mg/L TSS
Duration: 3 days (72 h) Temp: 10-13°C eggs;
14-17°C fingerlings PVC cups for containment
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Experiments and Endpoints
Two Phases►2010►2011
Northern and Southern Strains►Fingerlings – survival, coiling, scoliosis,
lordosis/kyphosis, gill integrity►Eggs – viability and hatchability, wet and dry mass
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2010 No. Viable Northern Strain Eggs
No significant differences among treatments were observed for viable eggs (Anova, F=0.38, P=0.7678).
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2010 No. Viable Southern Strain Eggs
No significant differences among treatments were observed for viable eggs (Anova, F=3.53, P=0.0681).
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Southern Strain Fingerling Survival
Fingerling survival did not differ significantly among TSS treatments (Anova, F=2.74, P=0.113).
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Northern Strain Fingerling Gill Lamellae
Fingerling gill lamellae did not differ significantly among TSS treatments.
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Percent Hatch of Northern Strain Eggs
No significant differences among treatments were observed for percent hatch (Anova, F=1.15, P=0.386).
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Number of Viable Northern Strain Eggs
No significant differences among treatments were observed for viable eggs (Anova, F=0.56, P=0.6533).
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Wet Mass Northern Strain Eggs
No significant differences among treatments were observed for viable eggs.
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These experimental data can be used with dredge plume characterization data that were obtained for bucket dredging in Maumee Bay to assess potential risk to walleye.
Current EW restrictions in Lake Erie may merit review in light of reduced uncertainty regarding risk associated with effect thresholds within the range of dredging-induced perturbations.
Implications
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