Relationship between water and aragonite barium concentrations in aquaria reared juvenile corals

This paper is not subject to U.S. copyright. The definitive version was published in Geochimica et Cosmochimica Acta 209 (2017): 123-134, doi:10.1016/j.gca.2017.04.006.Coral barium to calcium (Ba/Ca) ratios have been used to reconstruct records of upwelling, river and groundwater discharge, and sediment and dust input to the coastal ocean. However, this proxy has not yet been explicitly tested to determine if Ba inclusion in the coral skeleton is directly proportional to seawater Ba concentration and to further determine how additional factors such as temperature and calcification rate control coral Ba/Ca ratios. We measured the inclusion of Ba within aquaria reared juvenile corals (Favia fragum) at three temperatures (∼27.7, 24.6 and 22.5 °C) and three seawater Ba concentrations (73, 230 and 450 nmol kg−1). Coral polyps were settled on tiles conditioned with encrusting coralline algae, which complicated chemical analysis of the coral skeletal material grown during the aquaria experiments. We utilized Sr/Ca ratios of encrusting coralline algae (as low as 3.4 mmol mol−1) to correct coral Ba/Ca for this contamination, which was determined to be 26 ± 11% using a two end member mixing model. Notably, there was a large range in Ba/Ca across all treatments, however, we found that Ba inclusion was linear across the full concentration range. The temperature sensitivity of the distribution coefficient is within the range of previously reported values. Finally, calcification rate, which displayed large variability, was not correlated to the distribution coefficient. The observed temperature dependence predicts a change in coral Ba/Ca ratios of 1.1 μmol mol−1 from 20 to 28 °C for typical coastal ocean Ba concentrations of 50 nmol kg−1. Given the linear uptake of Ba by corals observed in this study, coral proxy records that demonstrate peaks of 10–25 μmol mol−1 would require coastal seawater Ba of between 60 and 145 nmol kg−1. Further validation of the coral Ba/Ca proxy requires evaluation of changes in seawater chemistry associated with the environmental perturbation recorded by the coral as well as verification of these results for Porites species, which are widely used in paleo reconstructions.M.E.G. was supported by a NDSEG graduate fellowship. Funding for this research came from the NSF Chemical Oceanography program (OCE-0751525) and the Coastal Ocean Institute, the Ocean and Climate Change Institute and the Ocean Ventures Fund at Woods Hole Oceanographic Institution

Folsom Mammoth Hunters? The Terminal Pleistocene Assemblage from Owl Cave (10BV30), Wasden Site, Idaho

The 1960s and 1970s excavations at Owl Cave (10BV30) recovered mammoth bone and Folsom-like points from the same strata, suggesting evidence for a post-Clovis mammoth kill. However, a synthesis of the excavation data was never published, and the locality has since been purged from the roster of sites with human / extinct megafauna associations. Here, we present data on bone from the oldest stratum, review provenience data, conduct a bone-surface modification study, and present the results of a protein-residue analysis. Our study fails to make the case for mammoth hunting by Folsom peoples. Although two of the fragments tested positive for horse or elephant protein, recent AMS dates indicate that all mammoth remains predate Folsom, and horse remains absent from the Owl Cave collection. Further, In unambiguously cultural surface modifications were identified on any of the mammoth remains. Given the available data, the Owl Cave deposits are most parsimoniously read as containing a Folsom-age occupation in the buried context, the first of its kind in the West West, but one nonetheless part of the Palimpsest of Pleistocene materials terminal

Climate-assisted persistence of tropical fish vagrants in temperate marine ecosystems

Laura Gajdzik et al. used population genomics, dietary DNA metabarcoding, and climate models to understand the influence of the 2010/2011 marine heatwave on the migration of rabbitfish from tropical environments into temperate environments in Western Australia. Their results reveal (i) little genetic differentiation and high migration rates between tropical residents and temperate vagrants, (ii) an overall diverse diet (including phytoplankton, local and widespread algae, and kelp), and (iii) projected suitable climate conditions for vagrants to establish in temperate marine waters