Download - Bivalve workshop May 2009
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Seasonal stable isotope composition of bivalve growth
increments and ambient water in the rivers Rhine and Meuse
Emma VersteeghHubert Vonhof, Simon Troelstra, Dick Kroon
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Freshwater mussels
Species: Unio pictorum & U. tumidus
Aragonite shells
Seasonal growth increments
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Oxygen isotopes
Meuse
Low δ18O in winter due to depleted precipitation
High δ18O in summer due to increased evaporation and enriched summer precipitation
Rhine
Additional factor: Alpine snow melt in summer → negative excursions in summer
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
δ18O rivers
Snow melt
High discharge
Flood
Dry summer
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Research questions
• Can shell incremental stable isotope chemistry be used as a proxy of past seasonal changes in river water composition?– Are δ18Oar values in shells in equilibrium with δ18Ow values of
ambient water?– Are seasonal δ13CHCO3- patterns within river water recorded in the
range of δ13C values within shell aragonite?
• Can we calculate intra-seasonal growth rates by matching relationships between stable oxygen and carbon isotope chemistry of river water and shell records?
• What are the environmental factors driving seasonal growth rate changes?
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring experiment: collecting and tagging Unionids
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring experiment: cages in fish ladders
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring locations
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Methods
• Water sampling
• Microsampling– Merchantek Micromill
• Stable isotopes– Finnigan Delta+ with
Gasbench II
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Predicted shell δ18O
Water δ18O & T → shell δ18O
1000 ln α = 2.559 (106 T-2) + 0.175
Grossman & Ku (1986); Dettman et al. (1999)
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Predicted shell δ18OMeuse Lek (Rhine distributary)
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
δ13C of HCO3-
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Shell δ18O records
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Shell δ13C records
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Matching shell and water records
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Matching shell and water records
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Intra-seasonal growth
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Conclusions• Unio pictorum and U. tumidus precipitate their
shell in oxygen isotopic equilibrium with ambient water
• Seasonal variation in δ13C values of dissolved inorganic carbon are recorded in shell aragonite
• Growth onset and cessation are induced by water temperature
• Growth rate is mainly influenced by food availability (primary productivity)
• Unionid stable isotope chemistry can serve as a proxy for past water composition (and related floods, droughts, primary productivity)
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Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Thank you!