Freshwater pearl mussels as a stream water stable isotope recorder

Abstract

For several decades, stable isotopes have been a commonly used and effective tool for flow path analysis, stream water source apportionment, and transit time analysis. The Global Network of Isotopes in Precipitation repository now has monthly precipitation isotope time series extending over several years and even decades in some settings. However, stream water isotope composition time series remain rather short with only very few data sets spanning over more than a few years. A critical challenge in this respect is the collection of stream water isotope data sets across a wide variety of headwater streams and for long durations. We rely on a new approach for stream signal reconstruction based on freshwater mussels, specifically the freshwater pearl mussel Margaritifera margaritifera. We use secondary ion mass spectrometry (SIMS) to quantify oxygen isotope ratios in pearl mussel shell growth bands. In our study area, the observed seasonal variability in precipitation δ18O values ranges between −15‰ and −3‰. This input signal is strongly damped in stream water, where observed values of δ18O range between −10‰ and −6.5‰. These values are consistent with our measured average shell‐derived stream water δ18O of −7.19‰. Along successive growth bands, SIMS‐based stream water δ18Ow values varied within a seasonal range of −9‰ to −5‰. The proposed SIMS‐based shell analysis technique is obviously well suited for analysing isotopic signatures of O in shell material—especially from the perspective of reconstructing historical series of in‐stream isotope signatures.

Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders

“…Similar to other marine (Epstein et al 1953;Mook & Vogel 1968;Killingley & Berger 1979) and freshwater bivalves (Dettman et al, 1999;Kaandorp et al 2003;Versteegh et al 2009;Pfister et al 2019), M. margaritifera forms its shell near equilibrium with the oxygen isotope composition of the water (δ 18 Ow) (Pfister et al 2018;Schöne et al 2005a). If the fractionation of oxygen isotopes between the water and shell carbonate is only temperature-dependent and the temperature during shell 80 formation is known or can be otherwise estimated (e.g., from shell growth rate), reconstruction can be made of the oxygen isotope signature of the water from that of the shell (δ 18 Os).…”

“…One new approach for hydroclimate reconstruction is the use of freshwater mussels as natural stream water stable isotope recorders (Dettman et al, 1999;Kelemen et al, 2017;Pfister et al, 2018Pfister et al, , 2019. Their shells can provide seasonally to annually resolved, chronologically precisely constrained records of environmental changes in the form of variable increment widths (= distance between subsequent growth lines) and geochemical properties (Nyström et al 1996;Schöne et al 2005a;Schöne and Krause, 2016;Geeza et al, in press a, b;Kelemen et al, in press).…”

Freshwater pearl mussels from northern Sweden serve as long-term, high-resolution stream water isotope recorders

“…One underutilized approach for hydroclimate reconstruction is the use of freshwater mussels as natural stream water stable isotope recorders (Dettman et al, 1999;Kelemen et al, 2017;Pfister et al, 2018Pfister et al, , 2019. Their shells can provide seasonally to annually resolved, chronologically precisely constrained records of environmental changes in the form of variable increment widths (which refers to the distance between subsequent growth lines) and geochemical properties (e.g., Nyström et al, 1996;Schöne et al, 2005a;Geist et al, 2005;Black et al, 2010;Schöne and Krause, 2016;Geeza et al, 2019Geeza et al, , 2020Kelemen et al, 2019).…”

“…Their shells can provide seasonally to annually resolved, chronologically precisely constrained records of environmental changes in the form of variable increment widths (which refers to the distance between subsequent growth lines) and geochemical properties (e.g., Nyström et al, 1996;Schöne et al, 2005a;Geist et al, 2005;Black et al, 2010;Schöne and Krause, 2016;Geeza et al, 2019Geeza et al, , 2020Kelemen et al, 2019). In particular, similar to marine (Epstein et al, 1953;Mook and Vogel, 1968;Killingley and Berger, 1979) and other freshwater bivalves (Dettman et al, 1999;Kaandorp et al, 2003;Versteegh et al, 2009;Kelemen et al, 2017;Pfister et al, 2019), Margaritifera margaritifera forms its shell near equilibrium with the oxygen isotope composition of the ambient water (δ 18 O w ) (Pfister et al, 2018;Schöne et al, 2005a). If the fractionation of oxygen isotopes between the water and shell carbonate is only temperature-dependent and the temperature during shell formation is known or can be otherwise estimated (e.g., from shell growth rate), reconstruction of the oxygen isotope signature of the water can be carried out from that of the shell CaCO 3 (δ 18 O s ).…”

“…If the fractionation of oxygen isotopes between the water and shell carbonate is only temperature-dependent and the temperature during shell formation is known or can be otherwise estimated (e.g., from shell growth rate), reconstruction of the oxygen isotope signature of the water can be carried out from that of the shell CaCO 3 (δ 18 O s ). Freshwater pearl mussels, M. margaritifera, are particularly useful in this respect, because they can reach a life span of 60 years (Pulteney, 1781) or 80 years (von Hessling, 1859) to over 200 years (Ziuganov et al, 2000;Mutvei and Westermark, 2001), offering an insight into long-term changes in freshwater ecosystems at an unprecedented temporal resolution.…”