Growth rate and age effects on Mya arenaria shell chemistry: Implications for biogeochemical studies

Abstract

The chemical composition of bivalve shells can reflect that of their environment, making them useful indicators of climate, pollution, and ecosystem changes. However, biological factors can also influence chemical properties of biogenic carbonate. Understanding how these factors affect chemical incorporation is essential for studies that use elemental chemistry of carbonates as indicators of environmental parameters. This study examined the effects of bivalve shell growth rate and age on the incorporation of elements into juvenile softshell clams, Mya arenaria. Although previous studies have explored the effects of these two biological factors, reports have differed depending on species and environmental conditions. In addition, none of the previous studies have examined growth rate and age in the same species and within the same study. We reared clams in controlled laboratory conditions and used solution-based inductively coupled plasma mass spectrometry (ICP-MS) analysis to explore whether growth rate affects elemental incorporation into shell. Growth rate was negatively correlated with Mg, Mn, and Ba shell concentration, possibly due to increased discrimination ability with size. The relationship between growth rate and Pb and Sr was unresolved. To determine age effects on incorporation, we used laser ablation ICP-MS to measure changes in chemical composition across shells of individual clams. Age affected incorporation of Mn, Sr, and Ba within the juvenile shell, primarily due to significantly different elemental composition of early shell material compared to shell accreted later in life. Variability in shell composition increased closer to the umbo (hinge), which may be the result of methodology or may indicate an increased ability with age to discriminate against ions that are not calcium or carbonate. The effects of age and growth rate on elemental incorporation have the potential to bias data interpretation and should be considered in any biogeochemical study that uses bivalves as environmental indicators. Published by Elsevier B.V.

Temperature and salinity effects on elemental uptake in the shells of larval and juvenile softshell clams Mya arenaria

“…Average shell lengths (± SE) from 15, 20, and 24°C treatments were 2.57 ± 0.13 mm, 3.10 ± 0.11 mm, and 5.05 ± 0.21 mm, respectively. Shell E:Ca did not vary significantly over this size range (Strasser et al 2008); we therefore assumed that shell size differences did not affect our results.…”

“…Gillikin et al (2005), however, carefully documented the relationship between environmental factors and Sr uptake in 2 species of marine bivalves with aragonitic shells and concluded that Sr:Ca ratios in shell are regulated by biological processes rather than thermodynamics. Studies of growth rate effects on Sr incorporation into Mya arenaria juvenile shell have produced both positive and negative correlations to growth rate for juvenile shells reared in the same conditions (Strasser et al 2008). These ambiguous results lend support to the idea that Sr incorporation may involve a number of physical and biological processes.…”

Influence of constant and periodic experimental hypoxic stress on Atlantic croaker otolith chemistry

“…Only Na:Ca was increased 2-fold on the sulcal axis, while Sr:Ca was similar between both axes. These patterns may have arisen simply due to differences in precipitation rates and therefore incorporation dynamics of elemental impurities (Strasser et al 2008, Walther et al 2010). In addition, other studies have quantified the elemental composition of the endolymph fluid from which the otolith is mineralized and found heterogeneity between dissolved elements and proteins in the proximal and distal regions of the endolymph (Payan et al 1999(Payan et al , 2004b.…”

Local-scale variation in trace elemental fingerprints of the estuarine bivalve Austrovenus stutchburyi within and between estuaries

“…A careful comparison of the results obtained from shell cleaned using the pre-ablation technique used here and other chemical cleaning techniques involving the use of hydrogen peroxide (e.g. Strasser et al 2008) should also be undertaken to determine the effect of cleaning methodology. Furthermore, multiple sampling events should be incorporated to understand how elemental fingerprints change over seasonal or annual scales.…”

“…Using stainless steel forceps, valves were split open, the flesh was removed and the shells were physically cleaned to remove any large adhering particles. Valves were placed into 50 ml centrifuge tubes filled with deionised water (which was maintained at a resistivity of <1 MΩ cm) and sonicated for 2 min to remove any remaining organic matter (Strasser et al 2008). The water was drained, and the shells were allowed to air dry.…”