egg production and egg viability of the copepods acartia...

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

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

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?

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?

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?

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

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

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

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

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

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

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

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

Egg viability

Acartia tonsa

Eurytemora carrolleeae

Ingestion


initial C:N:P


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

?

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

Egg viability

Acartia tonsa


Ingestion


initial C:N:P


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 ?

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



Carbon Carbon

Nitrogen Nitrogen


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


Egg viability

Acartia tonsa


Ingestion


initial C:N:P


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

?

-10

0

10

20

30 Day 1


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


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

)


Day 7


Egg viability

Acartia tonsa


Ingestion


initial C:N:P


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

?


-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 (

%)


Day 7

0

25

50

75

100

0 5 10 15 20

Eg

g v

iab

ilit

y (

%)


Day 7


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

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

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

Acknowledgements

• Jeff Alexander, Erica Kiss, Catherine Fitzgerald,

• Horn Point Laboratory Analytical Services

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

egg production and egg viability of the copepods acartia...

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