POSTCARDS FROM PREHISTORIC MARINE FOOD WEBS: NITROGEN ISOTOPES IN FISH OTOLITHS AS A PALEOECOLOGICAL ARCHIVE (Invited Presentation)

Fish otoliths, chronometric structures that comprise one component of the vestibular system of bony fishes, are preserved in archaeological and paleontological sediments around the globe. Otoliths contain an organic matrix produced by the fish when it was alive. Thus, otoliths are a potential archive of fish-native N isotopes (d15N), indicating fish diet and trophic level information, that may be available from the entirety of the otolith fossil record. Here, I present an overview and horizon scan of research that uses the d15N of contemporary and fossil otoliths. Following validation, I present applications on three time scales from the late Miocene to today. Respectively, these case studies use otolith d15N to (1) record N isotopic baseline (the N isotope composition of autotrophic biomass) using otoliths from marine sedimentary records spanning the last 12 million years (lanternfish study); (2) show the effects of biotic homogenization on Caribbean coral reef trophic structure over the Holocene (coral reef study); and (3) examine the effects of overfishing on a commercially targeted, collapsed fish population (archaeological Atlantic cod study). These studies illustrate the potential for reconstructing N isotope baseline, fish behavior, and fish trophic level in contexts where otoliths are preserved. In the future, d15N analyses will allow for reconstructing changes in fish ecology in response to past environmental changes, identifying fish movements across isotopically distinct environments now and in the past, and for glimpsing aspects of food web structure from previous warm periods in earth history.