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 Versteegh Hubert Vonhof, Simon Troelstra, Dick Kroon
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Transcript of Bivalve workshop May 2009
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
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Freshwater mussels
Species: Unio pictorum & U. tumidus
Aragonite shells
Seasonal growth increments
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
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
δ18O rivers
Snow melt
High discharge
Flood
Dry summer
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?
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring experiment: collecting and tagging Unionids
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring experiment: cages in fish ladders
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Monitoring locations
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Methods
• Water sampling
• Microsampling– Merchantek Micromill
• Stable isotopes– Finnigan Delta+ with
Gasbench II
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)
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Predicted shell δ18OMeuse Lek (Rhine distributary)
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
δ13C of HCO3-
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Shell δ18O records
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Shell δ13C records
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Matching shell and water records
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Matching shell and water records
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Intra-seasonal growth
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)
Bivalve Workshop, Vrije Universiteit Brussels, 4-5 May 2009
Thank you!
