Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts. These droughts have been linked to cool eastern tropical Pacific sea surface temperatures (SSTs). Here, we show both short-term and long-term climate variability over the last 1,500 y from annual band thickness and stable isotope speleothem data. Several megadroughts are evident, in...

Fluxes of organic matter across habitat boundaries are common in food webs. These fluxes may strongly influence community dynamics, depending on the extent to which they are used by consumers. Yet understanding of basal resource use by consumers is limited, because describing trophic pathways in complex food webs is difficult. We quantified resource use for zooplankton, zoobenthos, and fishes i...

of Dissertation.............................................................................iii Acknowledgements..................................................................................vi Chapter One...........................................................................................1 A test of geographic assignment using isotope tracers in feathers of known origin Chapter Two......

Here we describe stable isotope based models using hydrogen and carbon isotope ratios to predict geographic region-of-origin and growth environment for marijuana, with the intent of applying these models to analyses of marijuana trafficking in the USA. The models were developed on the basis of eradication specimens and border specimens seized throughout the USA. We tested reliability of the geo...

Stable isotope analysis has been used as a technique to analyse fisheries food webs for a quarter of a century, and remains the principal method for determining energy and nutrient pathways from primary producers to consumers in aquatic ecosystems. Carbon isotope analysis has been used to distinguish autotrophs at the base of inshore and offshore fisheries food webs. The combination of nitrogen...

By Brett M. Johnson Department of Fish, Wildlife and Conservation Biology, 1474 Campus Delivery, Colorado State University, Fort Collins, CO 80523-1474 Gregory W. Whitledge Fisheries and Illinois Aquaculture Center, Department of Zoology, Southern Illinois University, Carbondale, IL 62901-6511 and Patrick J. Martinez and Anita M. Martinez Colorado Division of Wildlife, 711 Independent Avenue, G...

The relationship between diet, geographic location and isotopic composition of human tissue has been successfully exploited in archaeological and palaeodietary studies, i.e. on ancient man, but cases in which this approach has been applied to present-day people e.g. to aid identification of mutilated or deteriorated bodies are far and few between. Stable isotope data are presented here from a c...

Variability in resource use defines the width of a trophic niche occupied by a population. Intra-population variability in resource use may occur across hierarchical levels of population structure from individuals to subpopulations. Understanding how levels of population organization contribute to population niche width is critical to ecology and evolution. Here we describe a hierarchical stabl...

An autonomous underwater vehicle (Seaglider) has been used to estimate marine primary production (PP) using a combination of irradiance and fluorescence vertical profiles. This method provides estimates for depth-resolved and temporally evolving PP on fine spatial scales in the absence of ship-based calibrations. We describe techniques to correct for known issues associated with long autonomous...