Karin Troost
Karin Troost
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 />
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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 />
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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 />
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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 />
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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 />
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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 />
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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 />
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