Tracing Water Sources of Terrestrial Animal Populations with Stable Isotopes: Laboratory Tests with Crickets and Spiders

Fluxes of carbon, nitrogen, and water between ecosystem components and organisms have great impacts across levels of biological organization. Although much progress has been made in tracing carbon and nitrogen, difficulty remains in tracing water sources from the ecosystem to animals and among animals (the “water web”). Naturally occurring, non-radioactive isotopes of hydrogen and oxygen in water provide a potential method for tracing water sources. However, using this approach for terrestrial animals is complicated by a change in water isotopes within the body due to differences in activity of heavy and light isotopes during cuticular and transpiratory water losses. Here we present a technique to use stable water isotopes to estimate the mean mix of water sources in a population by sampling a group of sympatric animals over time. Strong correlations between H and O isotopes in the body water of animals collected over time provide linear patterns of enrichment that can be used to predict a mean mix of water sources useful in standard mixing models to determine relative source contribution. Multiple temperature and humidity treatment levels do not greatly alter these relationships, thus having little effect on our ability to estimate this population-level mix of water sources. We show evidence for the validity of using multiple samples of animal body water, collected across time, to estimate the isotopic mix of water sources in a population and more accurately trace water sources. The ability to use isotopes to document patterns of animal water use should be a great asset to biologists globally, especially those studying drylands, droughts, streamside areas, irrigated landscapes, and the effects of climate change

Water isotopes in desiccating lichens

The stable isotopic composition of water is routinely used as a tracer to study water exchange processes in vascular plants and ecosystems. To date, no study has focussed on isotope processes in non-vascular, poikilohydric organisms such as lichens and bryophytes. To understand basic isotope exchange processes of non-vascular plants, thallus water isotopic composition was studied in various green-algal lichens exposed to desiccation. The study indicates that lichens equilibrate with the isotopic composition of surrounding water vapour. A model was developed as a proof of concept that accounts for the specific water relations of these poikilohydric organisms. The approach incorporates first their variable thallus water potential and second a compartmentation of the thallus water into two isotopically distinct but connected water pools. Moreover, the results represent first steps towards the development of poikilohydric organisms as a recorder of ambient vapour isotopic composition

Deuterium- und 18^{18}O-Gehalt im Kühlwasser von Kraftwerkskühltürmen

Deuterium- and $^{18}$O-content in the Cooling Water of Power Station Cooling Towers. The O-18/O-16 and D/H isotope ratios of water from two different cooling towers were determined by mass spectrometry. The observed isotope fractionation corresponds to that known from natural evaporation or transpiration processes:Cooling tower I: $\delta$(D) = 46.8 $^\circ$/$_{\circ}$$_{\circ}$ , 6($^{18}$O ) = 7.6 $^\circ$/$_{\circ}$$_{\circ}$ Cooling tower II: $\delta$(D) = 33.9 $^\circ$/$_{\circ}$$_{\circ}$, $\delta$($^{18}$O) = 5.7 $^\circ$/$_{\circ}$$_{\circ}$ Evaluation of simple compartment models of a cooling tower and a distillation device suggests that there exists some isotope discrimination within the open trickling unit of a cooling tower analogous to that in a rectification column. In areal coolingtower, however, this effect is compensated largely by the recycling of the cooling water, resulting only in a small enrichment of the heavy isotopes. This can be understood as the result of three partial effects: (I) a fractionation in the vapor pressure equilibrium, (II) a kinetic effect due to diffusion of the water vapor into a turbulent atmosphere, and (III) an exchange effect which is proportional to relative humidity. This low enrichment of the heavy isotope excludes the technical use of cooling towers as isotope separation devices

Die H2H_{2} 18O^{18}O- Anreicherung in den Blättern transpirierender Pflanzen und ihre Bedeutung für die stationäre 18O^{18}O-Überhöhung in der Atmosphäre

Eine wichtige Methode zur Aufklärung des Verhaltens komplexer Umweltsysteme besteht darin, in den einzelnen Reservoiren des Systems die relativen Isotopenhäufigkeiten der natürlichen Elemente, die das Ergebnis eines komplizierten Zusammenspiels einzelner elementarer Isotopieeffekte bei biologischen,geophysikalischen und geochemischen Prozessen sind, zu untersuchen. Isoliert man die Einzelprozesse und bestimmt ihre Isotopieeffekte, so kann man mit Hilfe geeigneter Modellvorstellungen den Gesamtprozess konstruierend nachvollziehen. Bei der Erforschung des Sauerstoffzyklus benutzt man als natürlichen Tracer das stabile 180-Isotop, dessen mittlere relative Häufigkeit 0.2039 % beträgt, während das Isotop $^{16}0$ den Hauptanteil mit 99.759 % stellt. $^{17}0$ wird nichtverwendet, da es einen Faktor 10 seltener als $^{18}O$ ist und außerdem kleinere Isotopieeffekte zeigt. Brauchbare radioaktive Sauerstoffisotope gibt es nicht.Die natürlichen Abweichungen der $^{18}O$-Konzentration von diesem Mittelwert liegen zwischen 0 und 30%o. Es sind bisher zahlreiche Isotopenhäufigkeitsanalysen von Sauerstoff unterschiedlicher Herkunft gemacht worden, insbesondere ist die stationäre $^{18}O$-Anreicherung in der Atmosphäre von 22%o relativ zum Meerwasser (SMOW), der DOLE-Effekt bekannt. Ihn zu erklären ist ein wichtiger Beitrag zum Verständnis des Sauerstoffzyklus. Für den DOLE-Effekt wurden bisher die respirativen Prozesse allein verantwortlich gemacht, da die Photosynthese keinen oder nur einen sehr geringen Effekt liefern sollte, wie Messungen an Wasserpflanzen nahelegten. Jedoch wurde der Beitrag der Photosynthese an Land hierbei übersehen. Denn während der Transpiration der Landpflanzen reichert sich aufgrund der unterschiedlichen Dampfdrücke das schwere Wasser in den Blättern, wo die Photosynthese stattfindet, an. Diese Isotopenüberhöhung sollte sich auch in dem freiwerdenden Photosynthesesauerstoff spiegeln. Meer und Atmosphäre stellen unterschiedliche Sauerstoffkompartimente dar, die durch Austauschprozesse miteinander in Wechselwirkung stehen. Dabei liefert die Landphotosynthese mit 2/3 der Gesamtassimilation den Hauptbeitrag zum DOLE-Effekt. [...

A high-resolution reference map for cytoplasmic and membrane-associated proteins of Corynebacterium glutamicum

We present a high-resolution reference map for soluble proteins obtained from Corynebacterium glutamicum cells grown in glucose minimal medium. The analysis window covers the p/ range from 4-6 and the molecular mass range from 5-100 kDa. Using overlapping narrow immobilized pH gradients for isoelectric focusing, 970 protein spots were detected after second-dimensional separation on SDS-polyacrylamide gels and colloidal Coomassie-staining. By tryptic peptide mass fingerprinting 169 protein spots were identified, representing 152 different proteins including many enzymes involved in central metabolism (18), amino acid biosynthesis (24) and nucleotide biosynthesis (11). Thirty-five of the identified proteins have no known function. A comparison of the observed and the expected physicochemical properties of the identified proteins indicated that nine proteins were covalently modified, since variants with apparently identical molecular mass, but differing p/ were detected. The N-termini of eight proteins were determined by post-source decay (PSD) analysis of selected peptides. In addition to the soluble proteins, a map of the membrane-bound proteins within the p/ range 4-7 is presented, which contains 660 protein spots, 22 of which were identified, representing 13 different proteins