Influence of hypoxia on the distribution, behavior, and foraging of zooplankton and planktivorous fish in centralLake Erie: Field observations & future directions
Hank Vanderploeg, GLERLStuart Ludsin, GLERLSteve Pothoven, GLERLTomas Höök, CILER Univ. of MichiganJames Roberts, Univ. of MichiganSteve Ruberg, GLERLJoann Cavaletto, GLERLJames Liebig, GLERLGregory Lang, GLERLStephen Brandt, GLERL
Hypoxia is an old problem in freshwater—Results forCyclops bicuspidatus (Einsle 1965)
This species is very tolerant of low oxygen (~ 0.1mg/L)
1. Hypoxia will disrupt vertical migration behavior
– Reduce time spent on bottom
2. Hypoxia will influence horizontal movement
– Fish will move into oxygenated, shallow nearshore zones
3. Hypoxia will reduce availability of prey, both ZP & benthic macroinvertebrate prey
– ZP use hypoxia as a refuge from predation– Hypoxia reduces benthic prey abundance
4. Fish consumption & condition will decline
Original Lake ErieFish-Centric Hypotheses
Playing chess with death—a zooplankton-centric view
Scene from Bergman’s “The Seventh Seal”
Death normally comes in two forms: predation and starvation
• Zooplankton vertical migration is strategy to minimize overlap with visually preying invertebrate and vertebrate (fish) predators—conspicuous or unprotected (spineless) zooplankton move to lower light levels
• Move into upper favorable (temperature and food) areas at night.
• Predator abundance is assessed by kairomones.• When many predators, the zooplankter (prey)
must play chess to avoid overlap.
The Great Lakes have both visual invertebrate & and vertebrate predators—Lake Michigan example
Playing chess with death—the piscine players
Scene from Bergman’s “The Seventh Seal”
Rainbow Smelt August 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
Emerald Shiner August 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
USGS-NAS
Emerald shiner:Epilimnetic planktivore
Rainbow Smelt:Planktivore-benthivore
Dominant planktivores of Lake Erie and their Vanderploeg & Scavia (1979) selectivity coefficients (W´) pre-hypoxia
Prey size
Hypoxia, another form of death, alters the game—some hypotheses:
• Differential tolerance of zooplankton to hypoxia allows some species to enter the hypoxic zone to escape predators—the refuge
• Others will be forced out and trapped in lighted areas above—the hypoxia-light trap.
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DissolvedOxygen(mg/l)
0
3
6
9
12
September
Diel Station B
August
Lake Erie
Some results before and after major hypoxia will give us some insights
General Methods—What we did
• Trawling (fish species & samples for diet & ration work)
• Zooplankton net and pump sampling (zooplankton)
• Ponar sampling (benthic macroinvertebrates)
• Zooplankton• Temperature• Dissolved oxygen• Light levels• Chlorophyll a
FishBiomass
Introduction to Study Systems & General Methods
Lake Erie Field Program (IFYLE 2005)
Diel (24-hr)Transect (day-night)
Source: Don Coles
EPA-GLNPOR/V Lake Guardian (180’)
NOAA-GLERLR/V Laurentian (80’)
Transect BDiel Station B
0 5 10 15 20 25D
epth
(m
)0
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Water Column Pumping Method
1 min. ea. depth
1 min. ea. depth
5 min.ea.
DO (mg/L)
Water Temp (oC)
2 min. ea. depth
Sept. 2005
shooting for pumping 1 cubic meter of water
DissolvedOxygen(mg/l)
0
3
6
9
12
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Transect B
Ho 2: Hypoxia will alter horizontal distribution of abundance– Fish will move into oxygenated, shallow nearshore zones
September
August
October
Lake Erie
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10
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- 5 0
- 3 0
Latitude (degrees)
Dep
th (
m)
Day
41.7 41.8 41.9 42 42.1
20
10
0
NightTemp(º C)
DO(mg/l)
Fish(dB)
6
1 4
2 2
3 0
(August – Pre-Hypoxia)
41.7 41.8 41.9 42 42.1
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0
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0
41.7 41.8 41.9 42 42.1
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0
41.7 41.8 41.9 42 42.1
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10
0
Ho 2: Hypoxia will alter horizontal distribution of abundance
Lake Erie
Ludsin, Vanderploeg & Ruberg, unpub
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0
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10
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- 1 1 0
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- 3 0
Latitude (degrees)
Dep
th (
m)
Temp(º C)
DO(mg/l)
Fish(dB)
6
1 4
2 2
3 0
41.7 41.8 41.9 42 42.1
20
10
0
41.7 41.8 41.9 42 42.1
20
10
0
41.7 41.8 41.9 42 42.1
20
10
0
(September – Peak Hypoxia)
Ho 2: Hypoxia will alter horizontal distribution of abundance
Day
41.7 41.8 41.9 42 42.1
20
10
0
Night
Lake Erie
Ludsin, Vanderploeg & Ruberg, unpub
0
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6
9
12
- 1 1 0
- 9 0
- 7 0
- 5 0
- 3 0
Latitude (degrees)
Dep
th (
m)
Temp(º C)
DO(mg/l)
Fish(dB)
6
1 4
2 2
3 0
41.6 41.7 41.8 41.9
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0
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41.7 41.8 41.9 42 42.1
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0
41.7 41.8 41.9 42 42.1
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10
0
41.7 41.8 41.9 42 42.1
20
10
0
(October – Post Hypoxia)
Ho 2: Hypoxia will alter horizontal distribution of abundance
Day
41.7 41.8 41.9 42 42.1
20
10
0Night
– Reject: Fish move into oxygenated waters, but offshore
Lake Erie
Ludsin, Vanderploeg & Ruberg, unpub
Playing chess with death—Insights from pre-hypoxia (control) & hypoxia distributions and prey selection
Scene from Bergman’s “The Seventh Seal”
Diel B, Aug 17, 01:00 EDT
0
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25
0 5 10 15 20 25
Chl, DO, Zoop, Temp
De
pth
(m
)
0 100 200 300 400 500PAR
Fish biomass(relative)
Zoomass (10 ug/L)
Chl (ug/L)
DO (mg/L)
Temp ('C)
PAR (uE/m2/s)
Diel B, Aug 17, 13:00 EDT
0
5
10
15
20
25
0 5 10 15 20 25Chl, DO, Zoop, Temp
De
pth
(m
)
0 200 400 600 800 1000 1200PAR
Fish biomass(relative)
Zoomass (10 ug/L)
Chl (ug/L)
DO (mg/L)
Temp ('C)
PAR (uE/m2/s)
Copepods mg . m-3
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dep
th
0
4
8
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24
Cladocerans mg . m-3
0 100 200
Lake Erie B 8-17-05 DIEL 02:00
BosminaEubosminaDaphnia mendotaeD. longiremis
Predatory Cladocerans mg . m-3
0 10 20 30
4.8 mg/L DO
EPI
META
HYPO
4.8 mg/L DO 4.8 mg/L DO
LeptodoraBythotrephesCercopagis
DiacyclopsMesocyclopsTropocyclopsDiaptomidsEpischuranauplii
Copepods mg . m-3
0 50 100
dep
th
0
4
8
12
16
20
24
DiacyclopsMesocyclopsTropocyclopsDiaptomidsEpischuranauplii
Cladocerans mg . m-3
0 20 40
Lake Erie B 8-17-05 DIEL 14:00
BosminaEubosminaDaphnia mendotaeD. longiremisD. retrocurva
Predatory Cladocerans mg . m-3
0 1 2
EPI
META
HYPO
4.8 mg/L DO 4.8 mg/L DO 4.8 mg/L DO
LeptodoraBythotrephes
Diel B, Sept 18, 03:00 EDT
0
5
10
15
20
25
0 5 10 15 20 25
Chl, DO, Zooplankton, Temp
De
pth
(m
)
0 100 200 300 400 500PAR
Fish biomass(relative)
Zoomass (10 ug/L)
Chl (ug/L)
DO (mg/L)
Temp ('C)
PAR (uE/m2/s)
Diel B, Sept 17, 15:00 EDT
0
5
10
15
20
25
0 5 10 15 20 25
Chl, DO, Zooplankton, Temp
De
pth
(m
)
0 100 200 300 400 500PAR
Fish biomass(relative)
Zomass (10 ug/L)
Chl (ug/L)
DO (mg/L)
Temp ('C)
PAR (uE/m2/s)
Predatory Cladocerans mg . m-3
0 1 2 3Copepods mg . m-3
0 100 200
dep
th
0
4
8
12
16
20
24
Cladocerns mg . m-3
0 20 40 60 80
Lake Erie B 9-18-05 DIEL 02:00
DiacyclopsMesocyclopsTropocyclopsDiaptomidsEpischuranauplii
BosminaEubosminaDaphnia mendotaeD. longiremisD. retrocurvaDiaphanasoma
Leptodora
upper epi
lower epi
meta
hypo
1.2 mg/L DO 1.2 mg/L DO 1.2 mg/L DO
Copepods mg . m-3
0 20 40 60 80
dep
th
0
4
8
12
16
20
24
Cladocerans mg . m-3
0 20 40
Lake Erie B 9-17-05 DIEL 14:00
DiacyclopsMesocyclopsTropocyclopsDiaptomidsEpischuranauplii
Predatory Cladocerans mg . m-3
0.0 0.5 1.0
1.2 mg/L DO 1.2 mg/L DO 1.2 mg/L DO
upper epi
lower epi
meta
hypo
BosminaEubosminaDaphnia mendotaeD. longiremisD. retrocurvaDiaphanasoma
Leptodora
Rainbow Smelt August 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
Emerald Shiner August 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
USGS-NAS
Emerald shiner:Epilimnetic planktivore
Rainbow Smelt:Planktivore-benthivore
Selectivity coefficient of Vanderploeg & Scavia (W´) for Emerald shiner and Rainbow Smelt in August 2005
Prey size
Rainbow Smelt September 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
Emerald Shiner September 2005
0.00
0.25
0.50
0.75
1.00
W' Night
Day
USGS-NAS
Emerald shiner:Epilimnetic planktivore
Rainbow smelt:Planktivore-benthivore
Prey size
Selectivity coefficient of Vanderploeg & Scavia (W´) for emerald shiner and rainbow smelt in September 2005
What’s going on down there?
Present status:Heavy emphasis in IFYLE Hypoxia study on upper
food web (fish and location of fish food)We do know, however:• Mesozooplankton and microzooplankton
distribution relative to hypoxia response is species specific
• Microzooplankton grazing dominates during the summer
• Bacteria-based food web becomes important in hypoxic zone
What’s going on down there?
For the development of a conceptual framework we’d like to know:
• What is the minimum oxygen concentration a zooplankter (species by species) is willing to enter yet survive under various predation risk scenarios?
• How does feeding and behavior vary with oxygen concentration?
• What is the joint distribution of meso-and microzooplankton around hypoxic zones
• How is production and predation risk affected?
We know something about Daphnia foraging in hypoxic areas but nothing for copepods, the dominants in the Great Lakes, or for visual
invertebrate predators
From Heisey & Porter (1977)
Some possible lab approaches to define spatial
rules of food web assembly (“indirect effects”)
• Observe location of position of zooplankton in laboratory water columns with gradients of light, temperature, kairomones of potential predators & oxygen
• Directly observe behavior and foraging in hypoxic water columns.
• Observe effect of hypoxia on visual predation (both invertebrate & vertebrate)—have predators watch TV
Inside the lab
Outside the lab: keeping the predator in focus
