Woods Hole Oceanographic Institution

Kelton McMahon

»Ocean Ecogeochemistry
»Estimating movement of marine animals
»Functional connectivity in a coral reef seascape
»Carbon isotopes identify snapper nursery habitat
»Otolith amino acid carbon isotope method
»Amino acid fractionation in fish tissues
»Stable isotope fractionation in fish muscle and otoliths
»Transequatorial Migrations by Basking Sharks
»Tracking top predator migration with isoscapes
»Bivalves as bioproxies for climate change
»Serries groenlandicus
»Digestibility of Ice algae and Phytoplankton
»Salt marsh fish movement and trophic dynamics

Kelton W. McMahon, Marilyn L. Fogel, Beverly J. Johnson, Leah A. Houghton, Simon R. Thorrold, A new method to reconstruct fish diet and movement patterns from δ13C values in otolith amino acids., Canadian Journal of Fisheries and Aquatic Sciences, 68:1330-1340, 2011

Fish ecologists have used geochemical signatures in otoliths to examine habitat use, migration, and population connectivity for decades. However, it remains difficult to determine an unambiguous dietary δ13C signature from bulk analysis of otolith. Studies to date have focused on the aragonite component of otoliths with less attention paid to the organic fraction. We describe the application of compound-specific stable isotope analysis (SIA) to analyze amino acid (AA) δ13C values from small amounts (<1 mg) of otolith powder. We examined δ13C values of otolith and muscle AAs from a reef-associated snapper (Lutjanus ehrenbergii) collected along a carbon isotope gradient (isoscape) from seagrass beds to coral reefs. Carbon isotope values in otolith and muscle samples were highly correlated within and among coastal habitats. Moreover, δ13C values of otolith AAs provided a purely dietary signature that avoided dilution from dissolved inorganic carbon. Otolith AAs served as a robust tracer of δ13C values at the base of the food web, making compound-specific SIA a powerful tool for dietary reconstructions and tracking the movement of fishes across isoscapes.

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