Role of Zooplankton in the Transformation, Remineralization, and Export of Particulate

Organic Matter in the Sea

Debbie Steinberg

Zooplankton particle cycling & remineralization

vertical migration(active transport)

fixation of C,Nby phytoplankton

grazing

egestion

C O2 , DOCNH4 , DONexcretion

respiration

consumption

Base of euphotic zone

egestion

disaggregation

C O2 , DOCNH4 , DON excretion

respiration

(molts, mucus,death)

xx

carnivory

microbial loop microbial loop

C O2 , DOCNH4 , DON

microbial loop

aggregateformation

excretion

respiration

Outline

Euphotic zone• JGOFS zooplankton grazing & flux estimates• Role of community composition

Below the euphotic zone• Vertical migration • Detritus as a food source and habitat for zooplankton• Zooplankton metabolic demand and C flux

Partitioning of energy consumed by zooplanktonIngestion

lost as DOM “sloppy feeding”

Excretion PRODUCTION= Growth + Reproduction

Respiration(metabolism)

Assimilation

Egestionas Feces

log10g= 0.0208[T] - 0.3221[log10BW] - 1.1408Production= growth x biomass

Ingestion= production/ 0.3 Egestion = ingestion x 0.3

(Hirst & Lampitt 1998)

0 10 20 30 40 50 60 70 80 90 100

HOT

BATS

Arabian Sea

EquatorialPacific

N. Atantic

S. OceanIngestion / PP

Feces Prod/export

Zooplankton grazing (as % PP)& Fecal pellet production (as % export flux)

103

(Roman et al. 2000, 2002; Morales et al. 1991,Dam et al.1993,1995; Le Borgne & Rodier 1997; Urban-Rich et al. 2001)

120

NEM (Jan)SWM (Aug/Sep)

340

El niño (Mar/Apr)Upwelling (Oct)

200

r2= 0.2

P< 0.001

r2= 0.06

NS

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600Zoop Biomass (mg/m2)

PO

C F

lux

(mg

C/m

2 /d)

Zooplankton Biomass (mg dw/m2)

Primary production vs. zooplankton biomass Zooplankton biomass vs. POC flux

biomass

0

100

200

300

400

500

600

0 500 1000 1500Primary Production (mg C/m2/d)

Zoo

plan

kton

Bio

mas

s (m

g dw

/m2 )

Primary Production (mg C/m2/d)

r2= 0.2

P< 0.001

r2= 0.06

NS

Salp bloom at BATS608 salps/ m3

1 mm

salp

euphausiid

copepod

Not all fecal pellets are created equal…

Average monthly salp bloom densitiesDensities

0.00

0.50

1.00

1.50

2.00

2.50

Jan Feb Mar Apr May June July Aug Sept Oct Nov DecMonths of the Year

199419951996199719981999

608263

Impact of Salp Blooms on 1o Production and Flux

GrazingSalp biomasstop 150 m

Primary Production0-140 m

% Primary Production

(mg C/m2) (mg C/m2 / day)

Mean 658 428 4%

Flux

Salp Ingestion=50% body C/ day

(mg C/m2 / day)

20

Mean salp biomasstop 150 m

POC Flux150 m

% Sinking POC Flux

(mg C/m2) (mg C/m2 / day)

36 33%

Salp Egestion=24% body C/ day(mg C/m2 / day)

12

Max 1433 1434 169%

1037%

Mean 658

Max 1433 75

716

344

n=57 blooms

Salp Fecal Pellets in 3200 m trap

Pleuromammaxiphias

Thysanopodaaequalis

Sergestes atlanticus

Common Vertical Migrators at BATS

Anchylomera blossevillei

Night : Day ratio of zooplankton biomass in top 200 m at BATS

0

1

2

3

4

1994 1995 1996 1997 1998

0

5

10

15

20

25

0 60 120 180 240

Time (min-1)

Mean gut passage times of vertical migrators

E. messinensis 114 min

T. aequalis 41 min

P. xiphias 186 min

(Schnetzer & Steinberg, 2002)

Comparison of active POC flux to passive POC flux

Morales (1999)Calculated -table IV

0.3- 6.7%150 mN Atlantic

Schnetzer & Steinberg (2002)

3%4%4%

150 m200 m300 m

BATS

Lampitt et al.(1993)2% 100 mNE Atlantic

Site Depth horizonActive POC flux as % passive flux Reference

Transport of dissolved material by migrators

euphausiids copepods

DOC

amphipods shrimp polychaete

CO2

N f Ta Ta Px Ab Ab Ss Sa N N

(µg

C/ m

g d

ry w

t./ h

r.)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

27

1742

28

14

16

2920

27

13

mean= 23%

(Steinberg et al. 2000)

% total C metabolized as DOC

Migratory active dissolved flux vs. passive POC flux Location Migrating biomass

(mg C/ m2)Migratory flux(% mean POC flux)

Reference

BATS 50 8 Steinberg et al. (2000)

Subtropical &Tropical Atlantic

- 6 Longhurst et al. (1990)

BATS 191 34 Dam et al. (1995)

North Atlantic (5-480) (19-40) Morales (1999)

HOT 142 15 Al-Mutairi & Landry (2001)

Eq. PacificMarch/April-October-

96 155

1825

Zhang & Dam (1997)

Oligotrophic-HNLC area-

47 53

8 4

LeBorgne & Rodier (1997)

Migrator remineralization ratios

P. xiphias(copepod)

N. Flexipes(euphausiid)

A. blossevillei(amphipod)

DOC:DON DIC:DIN

9

815

135

6

DIN:DIP DIC:DIN:DIP

16

16

7

6

15

95:16:1

118:16:1

91:7:1

106:16:16.6 6.6 16(Redfield)

(Steinberg et al., in press)

Video of mesopelagic zooplankton on detritus(not included for web)

Video of euphausiids disrupting particles(not included for web)

Comparison of zooplankton metabolic demands to sinking particle flux

•Zooplankton biomass in depth zone

•Weight specific respiration rate

•Determine C requirements for respiration:

µg C utilized = µl O2 consumed X 12 µg C X RQ (~0.8-1.0)1 µmol CO2= 22.4 µl

% flux remineralized by zooplankton = zooplankton C demand X 100%

loss of sinking particle C with depth

1)

•Weight specific ingestion rate (can stop here or...)

•Use AE (generally low ~10-50% for detritivore) and fraction respired ( ~ 50% of what is assimilated)

•Plug in above equation

2)

Examples from Literature

Banse (1990)King et al. (1978)

50-100%(mesozoop.)

70 - 200 mN.E. tropical Pacific

Koppelmann &Weikert (1999)

19-25% (spring)39-64% (summer)(mesozoop.)

1,000 - 4,250 mTemperate N.E. Atlantic

Steinberg et al. (1997)

2% (max 13%)6% (max 43%)(copepods)

Individual largeparticles 100 - 500 m

Coastal N.E. Pacific(Monterey Bay)

Lampitt (1992)9%(mesozoop. +micronekton)

100 -1,000 m above seabed(4,440m-5,340m)

Subtropical N. Atlantic

Sasaki et al. (1988)38%

(copepods)

150 -1,000 mN.W. Pacific(Oyashio)

Site Depth horizon

% sinking fluxConsumed or Remineralized

Reference

Summary•Zooplankton grazing and fecal pellet production varies with ocean basin & season

-grazing 3 - 50% of daily PP-fecal pellet production 5 - >100% of export flux

•Species composition important in determining export efficiency (e.g. salps)

•Zooplankton vertical migration increases flux via:-feces production at depth (but mean only 2 - 7 % of passive POC flux)-active transport of dissolved material (mean 4 - 40% of POC flux), fueling the microbial loop

•Zooplankton metabolic activity can account for a significant proportion of loss of POC with depth (9 -100% respired, 6 - 38% consumed)