Comparison of Solution‐Based versus Laser Ablation Inductively Coupled Plasma Mass Spectrometry for Analysis of Larval Fish Otolith Microelemental Composition

Abstract

Otolith microchemistry has become a widely used tool for fisheries-based research in marine systems. However, its application to systems without well-defined juvenile nursery areas in which distinct otolith elemental signatures can develop (i.e., most freshwater systems) remains limited. In large part, this deficiency is due to unsuitable protocols for reliably processing and analyzing small otoliths of larvae. Herein, we evaluate the abilities of solution-based (SO) and laser ablation (LA) inductively coupled plasma mass spectrometry (ICPMS) to quantify the otolith elemental composition of larval yellow perch Perca flavescens captured in three distinct spawning locations in Lake Erie (USA-Canada). Analysis of otolith pairs by each technique demonstrated that both SO-and LA-ICPMS could be used to reliably quantify the more abundant elements, such as Sr and Ba. Magnesium and zinc, analyzed by use of both SO-and LA-ICPMS, also met the criteria for inclusion in our analyses (i.e., the coefficients of variation of standards were ,10.5%, and over 90% of samples were above detection limits at a single location). Upon closer inspection of the data, however, we found that estimates of Mg and Zn were only reliable for LA-ICPMS. Estimates of these two elements using SO-ICPMS were unrealistically high, probably owing to contamination during the otolith dissolution and handling phases. We also found that LA-ICPMS provided more precise estimates than did SO-ICPMS for nearly all elements explored, but LA-ICPMS was somewhat limited by high limits of detection for some elements. Despite these differences, both techniques could accurately discriminate among larvae produced in different Lake Erie spawning locations, primarily because of the significant variation in Sr among larval otoliths. Ultimately, although both methods are appropriate for analysis of otoliths from larvae, we recommend the use of LA-ICPMS in future otolith microchemical applications involving larvae.

Sources of Nonnative Centrarchids in the Upper Colorado River Revealed by Stable Isotope and Microchemical Analyses of Otoliths

“…age 5) is indicative of interannual stability in water chemistry within habitats and demonstrates that differences in otolith Sr:Ca signatures of fish from riverine and high-salinity, floodplain pond habitats (up to 11 mmol/mol) can persist among years. These findings are consistent with previous research that demonstrated strong associations between water and otolith microchemistry (Wells et al 2003) and interannual stability of Sr:Ca signatures in some freshwater environments (Zimmerman and Reeves 2002;Wells et al 2003;Munro et al 2005;Ludsin et al 2006). …”

“…Our findings corroborate those of a few other recent studies that demonstrated that otolith microchemistry and isotopic analysis represent powerful techniques for retrospectively describing the environmental history of fishes that reside solely in freshwaters, including lakes (Joukhadar et al 2002;Brazner et al 2004;Munro et al 2005;Ludsin et al 2006), streams (Wells et al 2003), and small rivers (Bickford and Hannigan 2005). The results of this study demonstrate that otolith elemental and isotopic assays can also be applied to gain valuable insight into fish movement between large rivers and associated lentic floodplain habitats that would be difficult to obtain by other means.…”

“…Strontium concentrations were normalized to Ca concentration based on the consideration of calcium as a pseudointernal standard (Bickford and Hannigan 2005;Ludsin et al 2006); data are reported as Sr:Ca ratios (mmol/mol) for consistency with published otolith microchemistry literature and reflect differences in Sr concentration among samples. Mean limit of detection for 88 Sr was 0.09 lg/g; otolith 88 Sr concentrations ranged from 494 to 6,952 lg/g.…”

“…The significant positive relationship between otolith Sr:Ca ratio and salinity of ponds in our study area is probably the result 1266 of higher Sr concentrations in waters with elevated salinities; concentrations of both Sr and major salinityinfluencing ions are increased by evapotranspiration and influx of irrigation-derived water that has leached elements from Mancos shale underlying much of our study area (Gerner et al 2006). Otolith Sr concentration reflects that of the water in which fish live (Howland et al 2001;Zimmerman 2005); thus, our otolith Sr:Ca data are indicative of differences in Sr concentration among fish (and the environments in which they lived) because we treated Ca as an internal standard (Bickford and Hannigan 2005;Ludsin et al 2006). Strontium : calcium ratios for centrarchids of unknown history collected in riverine habitats were calculated based on integrations over entire laser transects when no evidence of fish movement from high-salinity to low-salinity environments was present (initial Sr:Ca 2.09 mmol/mol; Sr:Ca varied by ,0.5 mmol/mol from beginning to end of transect; Figure 2A).…”

Recruitment sources of invasive Bighead carp (Hypopthalmichthys nobilis) and Silver carp (H. molitrix) inhabiting the Illinois River

“…The laser ablated a transect extending from one side of the otolith core to the edge of the opposite side of the otolith along the longest axis of the section (beam diameter = 25 μm, scan rate = 5 μm/s, laser pulse rate = 20 Hz, laser energy level = 75%, wavelength = 266 nm). Otolith core (first 100 µm of the laser transect) Sr:Ca was used to identify natal environment for individual fish; mean otolith radius for age-0 fish ( Isotopic counts were converted to elemental concentrations (μg/g) after correction for gas blank, matrix, and drift effects (Ludsin et al 2006). Strontium concentration was normalized to calcium concentration based on the consideration of calcium as an internal standard and the stoichiometric concentration of calcium in aragonite for each species were evaluated using two-dimensional Kolmogorov-Smirnov (2DKS) tests (Garvey et al 1998).…”