Benthic calcification in the Dutch Benthic calcification in the Dutch North Sea area North Sea area

Frederic GazeauFrederic Gazeau

NIOO-CEMENIOO-CEME

Work in progress…… Maspalomas5/12/2006

CalcificationCalcification

► CaCa2+2+ + 2HCO + 2HCO33-- ↔ CaCO↔ CaCO33 + CO + CO2 2 + H+ H22OO

► Process realized by organisms such as corals, calcifying Process realized by organisms such as corals, calcifying macroalgae, foraminifera, echinoderms, pteropods, macroalgae, foraminifera, echinoderms, pteropods, coccolithophorids, molluscs….coccolithophorids, molluscs….

► Increased atmospheric pCOIncreased atmospheric pCO22 may threatened these may threatened these organismsorganisms BUT most studies focused on corals, macroalgae and BUT most studies focused on corals, macroalgae and

planktonic calcifiersplanktonic calcifiers

► Recent experiment showed preliminary evidences that Recent experiment showed preliminary evidences that molluscs calcification will be reduced under higher molluscs calcification will be reduced under higher atmospheric COatmospheric CO22 in the range of IPCC expectations for in the range of IPCC expectations for 21002100

► Very few estimates of benthic calcification in temperate Very few estimates of benthic calcification in temperate ecosystems over large areas (last to date: Smith, 1972 ecosystems over large areas (last to date: Smith, 1972 over the Southern California shelf)over the Southern California shelf)

0

-0.25

0.25

0.50

0

r2 = 0.87, P < 0.0001

0

250 500 750 1000 1250 1500-0.25

0.25

0.50

0

r2 = 0.80, P < 0.0001

pCO2 (ppmv)

Ne

t ca

lcifi

catio

n (

mo

l Ca

CO 3

g F

W-1

h-1

)

DatasetsDatasets

► 2 datasets used2 datasets used Netherlands Institute for Fisheries Research Netherlands Institute for Fisheries Research National Institute for Coastal and Marine Management / National Institute for Coastal and Marine Management /

RIKZRIKZ

► > 130,000 records, 2,500 sampling stations, area of > 60,000 > 130,000 records, 2,500 sampling stations, area of > 60,000 kmkm22

► Data of densities and fresh weights from 1990 to 2004Data of densities and fresh weights from 1990 to 2004

► Calcimass (g CaCOCalcimass (g CaCO33 m m-2-2) calculated from fresh weight ) calculated from fresh weight vs.vs. shell weight relationshipsshell weight relationships

► Gross calcification = calcimass x turnover (yrGross calcification = calcimass x turnover (yr -1-1))► Turnover data for major species provided by Joana Turnover data for major species provided by Joana

Cardoso (NIOZ)Cardoso (NIOZ)

Only intertidal areas sampled in the Westerschelde,Oosterschelde and Wadden Sea

0

2500

5000

7500

10000

Cerastoderma edule (71%)

Macoma balthica (19%)

Other species (10%)

A

Bio

mas

s (t

FW

)

10000

20000

30000

40000

Cerastoderma edule (74%)

Crassostrea gigas (14%)

Mytilus edulis (9%)

Other species (3%)

B

0

100000

200000

300000

Cerastoderma edule (56%)

Macoma balthica (19%)

Mytilus edulis (17%)

Other species (8%)

C

Bio

mas

s (t

FW

)

100000

200000

300000

400000

500000Spisula subtruncata (59%)

Ensis (16%)

Other species (18%)

D

Asterias rubens (7%)

Species counts

Westerschelde : 5 Oosterschelde: 7 Wadden Sea: 8 Coastal zone: 38

Cockles are very important in intertidal areas

In the 0-20m area Spisula subtruncata Ensis

BiodiversityBiodiversityWhat are the major species?What are the major species?

Westerschelde Oosterschelde

Wadden Sea Coastal zone0-20 m

BiodiversityBiodiversitydepths > 20mdepths > 20m

213 species!!!!!

Clear dominance of Echinoids

Work in progress

Fresh weight / Shell weightFresh weight / Shell weight

0 10 20 300

10

20

30Cerastoderma edule

Mytilus edulis

Crassostrea gigas

Macoma balthica

Spisula subtruncata

Ensis

Fresh weight (g)

Shel

l wei

ght (

g)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Tur

nove

r (P

/B in

yr

-1)

Cerastoderma edule

Mytilus edulis

Crassostrea gigas

Macoma balthica

Spisula subtruncata

Ensis

1 year

2 years

≥3 years

1 year

2 years

≥3 years

1 year

2 years

≥3 years

Turnover = Growth rateTurnover = Growth rate

Data from Joana Cardoso (NIOZ)

All data based on SHELL growth

OosterscheldeOosterschelde

► No large temporal variationsNo large temporal variations

► Cockles are the main producersCockles are the main producers

► BUT:BUT: Oysters were not well sampledOysters were not well sampled

► Kater (2003): Kater (2003): ► >300 g CaCO>300 g CaCO33 m m-2-2 yr yr-1-1

Important aquaculture site in Important aquaculture site in the Netherlands (oysters and the Netherlands (oysters and mussels)mussels)

► Based on production values Based on production values provided by the Dutch Fish provided by the Dutch Fish Product BoardProduct Board

Mussels: 100 g mMussels: 100 g m-2-2 yr yr-1-1

Oysters: > 500 g mOysters: > 500 g m-2-2 yr yr-1-1 19

9019

9219

9419

9619

9820

0020

0220

040

10

20

30

40

50

60

70

80

90Cerastoderma edule

Mytilus edulis

Year

G (

g C

aCO

3 m

-2 y

r-1)

Westerschelde estuaryWesterschelde estuary

► No aquacultureNo aquaculture

► Cockles are the main Cockles are the main producersproducers

► Very low calcimass and Very low calcimass and calcification ratescalcification rates

1992

1994

1996

1998

2000

2002

2004

0

5

10

15

20

25

Macoma balthicaCerastoderma edule

Year

G (

g C

aCO

3 m

-2 y

r-1)

Wadden SeaWadden Sea

► Large variations:Large variations: 5-155 g CaCO5-155 g CaCO33 m m-2-2 yr yr-1-1

► Wild mussels are the main producersWild mussels are the main producers

► Also an important site for Also an important site for aquacultureaquaculture

But large ecosystem (2700 kmBut large ecosystem (2700 km22)) Mussel culture covers 15% of the Mussel culture covers 15% of the

surface area of the Dutch surface area of the Dutch Wadden SeaWadden Sea

► 8 g CaCO8 g CaCO33 m m-2-2 yr yr-1-1 19

9019

9219

9419

9619

9820

0020

0220

040

100

200

Macoma balthicaMytilus edulis

Cerastoderma edule

Year

G (

g C

aCO

3 m

-2 y

r-1)

Coastal zone (0-20 m)Coastal zone (0-20 m)

► Very large variationsVery large variations

► Values between 1 and Values between 1 and 28 CaCO28 CaCO33 m m-2-2 yr yr-1-1

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

0

5

10

15

20

25

30

35Ensis

Spisula subtruncata

Year

G (

g C

aCO

3 m

-2 y

r-1)

Gross calcificationg CaCO3 m-2 yr-1

Cerastoderma edule 24 Mytilus edulis 11Crassostrea gigas* 328Culture Mytilus edulis 100Culture Crassostrea gigas 550Sub-Total ~1000

Cerastoderma edule 8 Macoma balthica 1 Sub-Total 9

Cerastoderma edule 21 Macoma balthica 1 Mytilus edulis 43

Culture Mytilus edulis 8Sub-Total 73

Spisula subtruncata 4 Ensis 6 Sub-Total 10

15 mmol CO2 m-2 d-1

Oosterschelde

Westerschelde

Wadden Sea

Coastal zone0-20 m

0.2 mmol CO2 m-2 d-1

1.2 mmol CO2 m-2 d-1

0.3 mmol CO2 m-2 d-1

Derived CO2 fluxes(ψ = CO2/CaCO3 of 0.6)

* Derived from Kater (2003)

Coastal zone> 20 m

Work in progress…….

Close to coral reefs estimates

Low values

Preliminary conclusionsPreliminary conclusions

► Aquaculture is very important and represents a main source of Aquaculture is very important and represents a main source of carbonate productioncarbonate production

► COCO22 production by gross calcification production by gross calcification► COCO22 production by shell burning production by shell burning

► Oosterschelde close to coral reef production (Milliman: 1500 g CaCOOosterschelde close to coral reef production (Milliman: 1500 g CaCO33 mm-2-2 yr yr-1-1))

► Small values for the coastal zone, Westerschelde estuary and Small values for the coastal zone, Westerschelde estuary and Wadden SeaWadden Sea

► A low total Dutch North Sea benthic calcification rate is expectedA low total Dutch North Sea benthic calcification rate is expected► < Milliman’s estimate for shelves (20-100)< Milliman’s estimate for shelves (20-100)► << Smith’s estimate for the Southern California shelf (400)<< Smith’s estimate for the Southern California shelf (400)

Future workFuture work

► Gross calcification in the >20m areaGross calcification in the >20m area► Shell removal by fisheries (Shell removal by fisheries (knownknown))► Estimates of shell removal by birds (Estimates of shell removal by birds (knownknown))► Data on shell weight in sediments (Data on shell weight in sediments (knownknown))

Together with sedimentation rates Together with sedimentation rates estimatesestimates

► Estimate of net accumulation rates and net Estimate of net accumulation rates and net COCO22 fluxes fluxes