Dentine oxygen isotopes (δ (18)O) as a proxy for odontocete distributions and movements.

Cory J D Matthews,Steven H Ferguson,Fred J Longstaffe

doi:10.1002/ece3.2238

Cory J D Matthews, Steven H Ferguson + Show 1 more

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https://doi.org/10.1002/ece3.2238

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Journal: Ecology and Evolution	Publication Date: Jun 8, 2016
Citations: 36	License type: CC BY 4.0

Affiliation: Crescent University, Western University

Abstract

Spatial variation in marine oxygen isotope ratios (δ 18O) resulting from differential evaporation rates and precipitation inputs is potentially useful for characterizing marine mammal distributions and tracking movements across δ 18O gradients. Dentine hydroxyapatite contains carbonate and phosphate that precipitate in oxygen isotopic equilibrium with body water, which in odontocetes closely tracks the isotopic composition of ambient water. To test whether dentine oxygen isotope composition reliably records that of ambient water and can therefore serve as a proxy for odontocete distribution and movement patterns, we measured δ 18O values of dentine structural carbonate (δ 18 OSC) and phosphate (δ 18 OP) of seven odontocete species (n = 55 individuals) from regional marine water bodies spanning a surface water δ 18O range of several per mil. Mean dentine δ 18 OSC (range +21.2 to +25.5‰ VSMOW) and δ 18 OP (+16.7 to +20.3‰) values were strongly correlated with marine surface water δ 18O values, with lower dentine δ 18 OSC and δ 18 OP values in high‐latitude regions (Arctic and Eastern North Pacific) and higher values in the Gulf of California, Gulf of Mexico, and Mediterranean Sea. Correlations between dentine δ 18 OSC and δ 18 OP values with marine surface water δ 18O values indicate that sequential δ 18O measurements along dentine, which grows incrementally and archives intra‐ and interannual isotopic composition over the lifetime of the animal, would be useful for characterizing residency within and movements among water bodies with strong δ 18O gradients, particularly between polar and lower latitudes, or between oceans and marginal basins.

Highlights

Toothed whales are widely distributed from tropical to polar regions, occupying coastal, shelf, and oceanic habitats (Forcada 2002)
Ecology and Evolution published by John Wiley & Sons Ltd
Mean dentine d18OSC values grouped by species within water body ranged from +21.2& to +25.5& (Atlantic spotted dolphins from the Gulf of Mexico; Table 2)

Summary

Introduction

Toothed whales (suborder Odontoceti) are widely distributed from tropical to polar regions, occupying coastal, shelf, and oceanic habitats (Forcada 2002). Despite the lack of apparent barriers to movement, many odontocetes display distinct structuring across their distributions, such as between coastal and offshore (Perrin 1984) or migratory and resident (Drouot et al 2004) populations. Temporal shifts in odontocete distributions generally reflect seasonal changes in habitat or prey distributions (e.g., Simil€a et al 1996; Forney and Wade 2006), while long-distance movements include dispersal from natal areas (Rice 1989) and migrations for breeding and purported physiological purposes (e.g., Durban and Pitman 2011). Defining residency and movement patterns is important for understanding the ecological (e.g., prey and competitor distributions), demographic

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