Otolith chemistry does not just reflect environmental conditions: A meta‐analytic evaluation

Abstract

Fish otoliths are widely used to answer biological and ecological questions related to movements and habitat use based on their chemical composition. Two fundamental assumptions underlie otoliths as environmental tracers and proxies for reconstructing exposure histories: (i) otolith chemistry reflects water chemistry, and (ii) ambient environmental conditions affect otolith element incorporation. Here, we test these assumptions for Sr and Ba through meta‐analyses. Our first meta‐analysis confirmed a correlation between concentrations of Sr:Ca and Ba:Ca in otoliths and the surrounding water, both elements displaying positive otolith–water correlations. The second meta‐analysis examined the relative influences of salinity and temperature on otolith Sr and Ba partition coefficients (an index of otolith element regulation). Our environmental effects meta‐analysis confirmed that otolith Sr and Ba are affected by temperature and salinity; however, study‐level covariates (e.g., water chemical concentrations and species ecological niche) influenced otolith element incorporation, and this varied by element. These findings confirm that even though otolith chemistry and elemental incorporation are differentially affected by environmental conditions, other factors play a decisive role. While we focused on studies that directly linked water and otolith chemistry, systematic reviews are key to further demonstrate the link between otolith chemistry and extrinsic and intrinsic factors. Ultimately, disentangling the relative effects of multiple factors on otolith chemistry and a detailed understanding of biomineralization is critical to the continued use of otoliths as natural tags for tracing fish movements and habitat use.

Spatial and temporal variation in otolith chemistry and its relationship with water chemistry: Stock discrimination of Sperata aor

“…A number of studies have reported the correlation between environmental exposure and otolith chemistry for Ba and Sr (Elsdon & Gillanders, 2004;Izzo, Reis-Santos, & Gillanders, 2018;Martin et al, 2013;Walther & Thorrold, 2006). The values of slope of the linear regressions estimated for Ba:Ca and Sr:Ca ratios (0.026 and 0.211 respectively in the present study) were nearly comparable to the earlier reported studies for a number of fish species such as…”

The Legacy of Hypoxia: Tracking Carryover Effects of Low Oxygen Exposure in a Demersal Fish Using Geochemical Tracers

“…Moreover, while intrinsic factors influence element incorporation into otoliths (Izzo et al. ), low DO (1.7 mg/L) alone did not result in elevated otolith Mn in Atlantic Croakers, suggesting extrinsic (i.e., sediment‐derived) Mn origins (Mohan et al. ).…”

Evaluating estuarine nursery use and life history patterns of Pomatomus saltatrix in eastern Australia

“…Fish from Clarence River may have had a higher proportion of crustaceans in their diet (due to their small size) than the fish from some of the other estuaries (Schilling et al 2017), and this may have been reflected by the high Ba:Ca ratios found for this group. However, this pattern was not seen in similarly small fish collected from Jervis Bay, suggesting, conversely, that diet had a limited impact on Ba:Ca ratios in this group (Izzo et al 2018). N evertheless, these patterns could simply reflect the higher freshwater input in Clarence River compared with in Jervis Bay.…”

“…temperature, salinity) factors in addition to a simple relationship with water chemistry (Sturrock et al 2014, Grammer et al 2017. A recent meta-analysis highlighted this by demonstrating that whilst salinity was the primary driver of both Ba and Sr, Sr was also influenced by factors including the ecological niche, condition, diet and ontogeny of individual species (Izzo et al 2018). As such, it is important to note that factors such as diet may be influencing the Sr:Ca profiles presented here (Engstedt et al 2012).…”