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Egg production and egg viability of the copepods Acartia and
Eurytemora differ when grown on food of varying nitrogen:phosphorus
ratios Katie Bentley James Pierson
Patricia M Glibert University of Maryland
Center for Environmental Science Horn Point Laboratory
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Nitrogen: Phosphorus ratios have increased
DIN
:TP
wt:
wt
0.00
0.02
0.04
0.06
0.08
0.10
1970 1980 1990 2000 2010
Ammonium
0.00
0.05
0.10
0.15
1970 1980 1990 2000 2010
Phosphate
0.0
1.0
2.0
3.0
4.0
5.0
1970 1990 2010
N:P ratio (wt:wt)
Mg
L-1
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Research Question
• Do changes in nutrient availability and proportion alter food quality for consumers?
• How are the nutrient content of copepods and eggs, egg production rates, and egg viability, affected by varying food quality?
?
?
?
?
Several symbols from Integration and Application Network,
University of Maryland Center for Environmental Science (ian.umces.edu/imagelibrary/).
Acartia tonsa
Eurytemora carolleeae
Ingestion
Thalassiosira pseudonana
initial C:N:P
Media Nutrient supply
C:N:P C:N:P
C:N:P
C:N:P
Excretion
Egg production
Egg viability
Nutrient released
C:N:P
C:N:P
C:N:P
C:N:P C:N:P
C:N:P
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Copepods
• Eurytemora carolleeae - brood spawners
– lay their eggs in sacs that develop attached to females
• Acartia tonsa - broadcast spawners
– release large numbers of eggs to environment
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Hypotheses • While phytoplankton nutrient content can be quite
variable, due to their ability to take up and store nutrient in excess of their growth requirement, copepod nutrient content should not vary substantially with prey nutrient content.
• Copepods should maintain relatively invariant nutrient content because their excretion, and egg nutrient content should change as diet changes
• As diet changes, and as egg nutrient content changes, egg production rates and egg viability should change
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A B C
Diatom growth,
variable N:P
experimental
exposures with
zooplankton
1
2
8 laboratory experiments conducted: Diatom grown at 4 N:P ratios Exposed to 2 zooplankton: Eurytemora and Acartia at same total food amount (in terms of C)
1:20 dilution
culture:ASW
Methods
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PN PC PP Chla
CELL
COUNTS PC PN PP
A B C
phytoplankton
growth,
variable N:P
experimental
exposures with
zooplankton
time dependent
chemical
measurements
1 3
2
1:20 dilution
culture:ASW
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PN PC PP Chla
CELL
COUNTS PC PN PP
A B C
phytoplankton
growth,
variable N:P
experimental
exposures with
zooplankton
time dependent
chemical
measurements
1 3
2
4
egg
chemical
composition
1:20 dilution
culture:ASW
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PN PC PP Chla
CELL
COUNTS PC PN PP
A B C
phytoplankton
growth,
variable N:P
experimental
exposures with
zooplankton
time dependent
chemical
measurements
1 3
2
4 5
egg
chemical
composition
egg viability
1:20 dilution
culture:ASW
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PN PC PP Chla
CELL
COUNTS PC PN PP
A B C
phytoplankton
growth,
variable N:P
experimental
exposures with
zooplankton
time dependent
chemical
measurements
1 3
2
4 5
egg
production,
chemical
composition egg viability
1:20 dilution
culture:ASW
Repeat after copepods exposed for 7 days to food of experimentally determined food quality
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Egg viability
Acartia tonsa
Eurytemora carrolleeae
Ingestion
Thalassiosira pseudonana
initial C:N:P
Media Nutrient supply
C:N:P C:N:P
C:N:P
Excretion
Egg production
Nutrient released
C:N:P
C:N:P
C:N:P
C:N:P
C:N:P
?
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0.00
1.00
2.00
3.00
μg
ram
s N
co
pe
po
d-1
0.00
5.00
10.00
15.00
20.00μ
gra
ms
C c
op
ep
od
-1
0.00
0.10
0.20
0.30
0.40
0.00 5.00 10.00 15.00 20.00
μg
ram
s P
co
pe
po
d-1
0.00
5.00
10.00
15.00
20.00
0.00
1.00
2.00
3.00
0.00
0.10
0.20
0.30
0.40
0.00 5.00 10.00 15.00 20.00
Acartia tonsa Eurytemora carolleeae
prey cellular N:P (molar:molar) prey cellular N:P (molar:molar)
Carbon Carbon
Nitrogen Nitrogen
Phosphorus Phosphorus
HIGH P HIGH N HIGH P HIGH N
Copepod
nutrient
content
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Egg viability
Acartia tonsa
Eurytemora carrolleeae
Ingestion
Thalassiosira pseudonana
initial C:N:P
Media Nutrient supply
C:N:P C:N:P
C:N:P
Excretion
Egg production
Nutrient released
C:N:P
C:N:P
C:N:P
C:N:P
C:N:P ?
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Egg
nutrient
content 0.00
0.50
1.00
1.50
2.00μ
g C
eg
g-1
0.00
0.04
0.08
0.12
μg
N e
gg
-1
0.000
0.004
0.008
0.012
0.00 5.00 10.00 15.00 20.00
mg
P e
gg
-1
0.00
0.50
1.00
1.50
2.00
0.00
0.04
0.08
0.12
0.000
0.004
0.008
0.012
0.00 5.00 10.00 15.00 20.00
prey cellular N:P (molar:molar)
Acartia tonsa Eurytemora carrolleeae
prey cellular N:P (molar:molar)
HIGH P HIGH N HIGH P HIGH N
Carbon Carbon
Nitrogen Nitrogen
Phosphorus Phosphorus
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Egg nutrient
content as
a function
of copepod
nutrient
content
0.000
0.004
0.008
0.012
0.00 0.10 0.20 0.30 0.40
Eg
g P
(μ
g P
eg
g-1
)
Copepod P (μg P copepod-1)
0.00
0.05
0.10
0.15
0.00 1.00 2.00 3.00
Eg
g N
(μ
g N
eg
g-1
)
Copepod N (μg N copepod-1)
0.00
0.05
0.10
0.15
0.00 1.00 2.00 3.00
Eg
g N
(μ
g N
eg
g-1
)
Copepod N (μg N copepod-1)
0.0
0.5
1.0
1.5
2.0
0.00 5.00 10.00 15.00Eg
g C
(μ
g C
eg
g -
1)
Copepod C (μg C copepod-1)
0.0
0.5
1.0
1.5
2.0
0.00 5.00 10.00 15.00Eg
g C
(μ
g C
eg
g-1
)
Copepod C (μg C copepod-1)
0.000
0.004
0.008
0.012
0.00 0.10 0.20 0.30 0.40
Eg
g P
(μ
g P
eg
g-1
)
Copepod P (μg P copepod-1)
Acartia tonsa Eurytemora
carrolleeae Carbon Carbon
Nitrogen Nitrogen
Phosphorus Phosphorus
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Egg viability
Acartia tonsa
Eurytemora carrolleeae
Ingestion
Thalassiosira pseudonana
initial C:N:P
Media Nutrient supply
C:N:P C:N:P
C:N:P
Excretion
Egg production
Nutrient released
C:N:P
C:N:P
C:N:P
C:N:P
C:N:P
?
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-10
0
10
20
30 Day 1
Acartia tonsa Eurytemora carrolleeae
0.0
1.0
2.0
3.0
4.0
Eg
g p
rod
uc
tio
n
(eg
gs
fe
ma
le-1
da
y-1
)
Day 1
-10
0
10
20
30
0 5 10 15 20
prey cellular N:P (molar:molar)
Day 7
0.0
1.0
2.0
3.0
4.0
0 5 10 15 20
Eg
g p
rod
uc
tio
n
(eg
gs
fe
ma
le-1
da
y-1
)
prey cellular N:P (molar:molar)
Day 7
HIGH P HIGH N HIGH P HIGH N
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Egg viability
Acartia tonsa
Eurytemora carrolleeae
Ingestion
Thalassiosira pseudonana
initial C:N:P
Media Nutrient supply
C:N:P C:N:P
C:N:P
Excretion
Egg production
Nutrient released
C:N:P
C:N:P
C:N:P
C:N:P
C:N:P
?
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Acartia tonsa Eurytemora carrolleeae
-25
0
25
50
75
100
Eg
g v
iab
ilit
y (
%)
Day 1
0
25
50
75
100
Eg
g v
iab
ilit
y (
%) Day 1
-25
0
25
50
75
100
0 5 10 15 20
Eg
g v
iab
ilit
y (
%)
prey cellular N:P (molar:molar)
Day 7
0
25
50
75
100
0 5 10 15 20
Eg
g v
iab
ilit
y (
%)
prey cellular N:P (molar:molar)
Day 7
HIGH P HIGH N HIGH P HIGH N
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Low P
Excretion
Acartia
tonsa
Egg
viability
Egg
production
N:P
Low P
Excretion
Eurytemora
carrolleeae
Egg
viability
Egg
production
N:P
N:P
N:P
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High P
Excretion
Acartia
tonsa
Egg
viability
Egg
production
N:P
N:P
High P
Excretion
Eurytemora
carrolleeae
Egg
viability
Egg
production
N:P
N:P
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Conclusions
• Acartia and Eurytemora differed in their tissue nutrient content and in their response to variable nutrient quality in their food
• Variable nutrient quality in the diatom prey affected egg production and egg viability even when food quantity (C) was constant and provided in excess
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Acknowledgements
• Jeff Alexander, Erica Kiss, Catherine Fitzgerald,
• Horn Point Laboratory Analytical Services
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0
5
10
15
20
0 10 20 30 40
Ce
llu
lar
N:P
(m
ola
rr)
N:P media (molar)
Prey cellular N:P