PNNL

Abstract

Water microchemistry combines geologic and hydrologic factors and has been increasingly used to delineate regions within watersheds. These chemical signatures are also incorporated into chronologically layered calcified structures of biological organisms and can be used to retrace species’ life history. Strontium (Sr), barium (Ba), manganese (Mn) and 87Sr/86Sr ratios have been useful for microchemical characterization because of their relationship to underlying substrates, gradients in their relative abundance within watersheds, and large concentration differences between fresh and saline water. In the Pearl and Pascagoula River systems of Mississippi and Louisiana, USA, an understanding of microchemistry would benefit research on the life history of species of management importance, such as the Federally threatened Gulf Sturgeon (Acipenser desotoi). Therefore, Sr, Ba, Mn and 87Sr/86Sr were measured across these watersheds in multiple years using solution inductively coupled-mass spectrometry (ICP-MS) to create or expand watershed microchemistry maps. The relative interannual variability was low (generally