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Karin Troost

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IMARES<br />

Changes induced by expansion of the ecosystem<br />

engineer and invasive species Crassostrea gigas in<br />

continental NW European estuaries<br />

<strong>Karin</strong> <strong>Troost</strong>


txtColonization and spread in NW Europe<br />

• txt<br />

Norway 1979<br />

Sweden 1973<br />

Denmark 1972<br />

Wrange et al. 2009<br />

Reise 1998<br />

Wehrmann et al. 2000<br />

Nehls et al. 2006<br />

Diederich et al. 2005<br />

Germany 1971<br />

Smaal et al. 2009<br />

Dankers et al. 2006<br />

Netherlands 1964<br />

Belgium 1969<br />

Drinkwaard 1999<br />

<strong>Troost</strong> 2010<br />

Kerckhof et al. 2007<br />

IMARES<br />

IMARES


The Pacific oyster Crassostrea gigas<br />

<strong>Karin</strong> <strong>Troost</strong> (2010) “Causes and effects of a highly successful marine invasion: Casestudy<br />

of the introduced Pacific oyster Crassostrea gigas in continental NW European<br />

estuaries” Journal of Sea Research 64: 145 - 165<br />

IMARES


Changes induced due to<br />

Large filtration capacity<br />

• Carrying capacity<br />

• Larviphagy<br />

Habitat modification<br />

• Ecosystem engineer<br />

• Competition for space<br />

• Habitat heterogeneity<br />

IMARES


Changes due to filtration activity<br />

Carrying capacity<br />

Oosterschelde estuary:<br />

- Long water residence time<br />

- Large bivalve stocks<br />

IMARES


stock size<br />

(million kg fresh weight)<br />

Changes due to filtration activity<br />

Carrying capacity<br />

Oosterschelde estuary: Increase total filter feeder stock<br />

Increase filtration pressure<br />

Total filter-feeder stock (3 dominant species)<br />

year<br />

<strong>Troost</strong> et al. 2009, J. Sea Res. 61: 153 - 164<br />

IMARES


Changes due to filtration activity<br />

Carrying capacity<br />

Oosterschelde estuary: Increase total filter feeder stock<br />

Increase filtration pressure<br />

Carrying capacity reached?<br />

• filtration time total volume 2 750 million m 3 :<br />

10 days in 1990 7 days in 2000<br />

• turnover time phytoplankton 5 days<br />

• shift to smaller phytoplankton species = ‘overgrazing’<br />

• decreasing growth and condition cultured bivalves<br />

Geurts van Kessel et al. 2003<br />

<strong>Troost</strong> et al. 2009, J. Sea Res. 61: 153 - 164<br />

IMARES


CR (l h -1 g -1 afdw)<br />

Changes due to filtration activity<br />

Larviphagy<br />

Oosterschelde estuary: Increase total filter feeder stock<br />

Increase filtration pressure<br />

increased predation on bivalve larvae (“larviphagy”)<br />

mortality due to larviphagy estimated at 95%<br />

<strong>Troost</strong> et al. 2009, J. Sea Res. 61: 153 - 164<br />

25<br />

20<br />

CR on algae<br />

CR on mussel larvae<br />

25<br />

20<br />

CR on algae<br />

CR on oyster larvae<br />

15<br />

15<br />

10<br />

10<br />

5<br />

5<br />

0<br />

cockle mussel oyster<br />

0<br />

cockle mussel oyster<br />

<strong>Troost</strong> et al. 2008 J. Sea Res. 60<br />

<strong>Troost</strong> et al. 2008 IMARES JEMBE 358


Changes due to habitat modification<br />

Ecosystem engineering<br />

Cuddington & Hastings 2004<br />

Jones 1994<br />

Adaptation of habitat to own demands by reef formation:<br />

• gregarious settlement of larvae<br />

• preferential settlement on oyster shells<br />

• larvae attracted to adults<br />

• larvae attracted to previously settled spat<br />

• spat cemented to adults<br />

Diederich 2005<br />

Tamburri et al. 2007<br />

<strong>Troost</strong> 2009<br />

persistent 3D reef structure<br />

IMARES


Changes due to habitat modification<br />

Competition for space<br />

Pacific oyster highly competitive for space<br />

But:<br />

• Coexists with M. edulis in mixed beds<br />

• Not complete niche overlap with other bivalves<br />

• Resource not limited<br />

Competition for space only on local scale<br />

13<br />

<strong>Troost</strong> 2010, J. Sea Res. 64: 145 - 165<br />

IMARES<br />

IMARES


Changes due to habitat modification<br />

Habitat heterogeneity<br />

<strong>Troost</strong> 2010<br />

Buschbaum et al. 2009<br />

Commito & Dankers 2001<br />

Photo courtesy Peter Paul Stehouwer<br />

• settlement opportunities<br />

• shelter<br />

• increased habitat heterogeneity<br />

increased biodiversity<br />

Kochmann et al. 2008<br />

Markert et al. 2009<br />

Photo courtesy Johan van de Koppel<br />

IMARES<br />

IMARES


Changes due to habitat modification<br />

Effects on higher trophic levels: shore birds<br />

• C. gigas hardly eaten by birds<br />

• role oyster beds as foraging area uncertain<br />

• maybe problem for birds dependent on mussels<br />

• some birds learn to feed on C. gigas, locally<br />

26<br />

Scheiffarth et al. 2007<br />

Cadée 2001, 2008<br />

<strong>Troost</strong> 2010<br />

IMARES


Opportunities ?<br />

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Opportunities for restoration<br />

• Loss habitat building species & associated communities NW<br />

European estuaries due to overexploitation in 20 th century<br />

(seagrass, O. edulis oyster beds, Sabellaria reefs, sea moss, mussel beds)<br />

• Pacific oyster beds reintroduce structural complexity<br />

and habitat heterogeneity<br />

Restoration biodiversity<br />

Reise 1982<br />

Wolff 2000<br />

Lotze 2005<br />

Airoldi & Beck 2007<br />

<strong>Troost</strong> 2010, J. Sea Res. 64: 145 - 165<br />

IMARES


Opportunities for coastal defence<br />

• Stabilization sediments<br />

• Reduction wave energy<br />

• Sedimentation<br />

protection tidal flats against erosion<br />

Tom Ysebaert & Brenda Walles<br />

IMARES


Conclusions<br />

Although biological invasions threaten global biodiversity<br />

and may cause large ecological and economical damage ...<br />

... the case-study of the Pacific oyster in NW Europe shows that<br />

ecosystem engineering invaders may also contribute to ecological<br />

complexity and restoration of biodiversity<br />

IMARES


I thank<br />

YOU for your attention!<br />

and<br />

Wim Wolff – University of Groningen<br />

Pauline Kamerman – IMARES<br />

Eize Stamhuis – University of Groningen<br />

Peter Herman – NIOO-CEME<br />

Aad Smaal – IMARES<br />

Luca van Duren – Deltares<br />

Maria van Leeuwe - Wadden Sea Society<br />

NWO – ALW<br />

28<br />

IMARES

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