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Ökologie

Die Stabilisotopenanalyse einer Vielzahl von Materialien im Bereich der Ökologie erlaubt es Forschern, Informationen zu gewinnen, die mit anderen analytischen Methoden nicht erzielt werden können. Stabile Isotope werden von Ökologen häufig als Tracer in biologischen Systemen eingesetzt, um Elementkreisläufe in einem Ökosystem nachzuvollziehen. Variationen in der Isotopensignatur in unterschiedlichen geographischen Regionen erlauben es, Isotopen als Tracer für Migration zu nutzen, während mit Hilfe des Prinzips der Isotopenfraktionierung biogeochemische Prozesse in einer solchen Detailgenauikgeit analysiert werden können, die von der Betrachtung der Elementzusammensetzung alleine nicht erreicht werden kann.

So können z.B. Kohlenstoffisotope genutzt werden, um die Primärenergiequelle in einem Ökosystem zu bestimmen, wohingegen Stickstoffisotope nützlich sind, um die trophische Ebene eines Organismus zu identifizieren. Schwefelisotope können benthische Produzenten von pelagischen unterscheiden, ebenso wie Sumpfpflanzen von Phytoplanktonproduzenten.

Die Entwicklung unseres Verständnisses dieser immanenten Beziehungen zwischen lebenden Organismen und ihrer Umgebung durch die Stabilisotopenanalyse unterstützt unseren sorgfältigen Umgang mit der natürlichen Welt um zu gewährleisten, dass künftige Generationen die gleichen Wunder erleben wie wir heute.

Publikationen zum Thema Ökologie mit unseren Geräten

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155 Ergebnisse:

Inferring the timing of long-distance dispersal between rail metapopulations using genetic and isotopic assignments
Ecological Applications (2016)
Laurie A. Hall, Steven R. Beissinger

The stochastic and infrequent nature of long-distance dispersal often makes it difficult to detect. We quantified the frequency, distance, and timing of long-distance dispersal in a non-migratory, secretive wetland bird, the California black rail (Laterallus jamaicensis coturniculus), between an inland and a coastal metapopulation separated by greater than 100 km. Using 15 microsatellites in conjunction with stable carbon, nitrogen, and sulfur isotopes, we classified rails as: residents of their capture population, recent migrants that dispersed to their capture population less than one year before capture, established migrants that dispersed to their capture population more than one year before capture, and seasonal migrants that dispersed away from their capture population to forage, but returned the next season. Most rails (195 of 204 or 95.6%) were classified as residents, but we detected two established migrants that had moved >100 km more than a year before capture. Seven rails appeared to be seasonal migrants, but comparisons of feather isotope values with isotope values from wetland soils indicated that the isotope values in the feathers of these rails likely resulted from natural environmental variation (e.g., source element effects) rather than long-distance dispersal of individuals. Thus, these seven rails were most likely misassigned by isotopic population assignments due to small-scale variation in the isoscape. Using genetic data in conjunction with isotopic data allowed us to not only infer the timing of long-distance dispersal events, but to successfully track long-distance movements of non-migratory rails between metapopulations even when environmental variation of isotopes occurred across small spatial scales.
Schlagworte: carbon , nitrogen , sulfur , ecol , elem

Palaeoecological evidence for sustained change in a shallow Murray River (Australia) floodplain lake: regime shift or press response?
Hydrobiologia (2016)
Giri Kattel, Peter Gell, Atun Zawadzki, Linda Barry

Paleolimnological techniques can reveal long-term perturbations and associated stable state transitions of lake ecosystems. However, such transitions are difficult to predict since changes to lake ecosystems can be abrupt or gradual. This study examined whether there were past transitions in the ecological regime of Kings Billabong, a shallow River Murray wetland in southeast Australia. A 94-cm-long core, covering c. 90 years of age, was analysed at 1 cm resolution for subfossil cladocerans, diatoms and other proxies. Prior to river regulation (c. 1930), the littoral to planktonic ratios of cladocerans and diatoms, and bulk sediment δ13C values were high, while the period from c. 1930 to c. 1970 experienced considerable changes to the wetland ecosystem. The abrupt nature of changes of planktonic cladocerans and diatoms, particularly after the onset of river regulation (1930s), was triggered by inundation, high rates of sedimentation and shifts in bulk sediment δ15N values. However, the transition of a once littoral-dominated community, to one favouring an increasingly turbid, plankton-dominated trophic condition following river regulation was relatively slow and lasted for decades. The progression to a new regime was likely delayed by the partial recovery of submerged plant communities and related internal dynamics.
Schlagworte: carbon , nitrogen , geol , ecol , elem

Impact of river regulation and hydropeaking on the growth, condition and field metabolism of Brook Trout ( Salvelinus fontinalis )
Ecology of Freshwater Fish (2016)
Brianne Kelly, Karen E. Smokorowski, Michael Power

Brook Trout (Salvelinus fontinalis) is an important fish species in Ontario, Canada, supporting recreational fisheries that contribute significantly to local economies. Hydroelectric dams disrupt the river continuum, altering downstream conditions and impacting riverine fish populations. Specifically, Brook Trout activity has been found to increase during hydropeaking periods, when dam operators rapidly increase river discharge to meet electricity demands. Higher energetic outputs driven by hydropeaking may decrease the energy available to allocate towards fish growth and condition, negatively impacting Brook Trout. We investigated the impact of two different hydropeaking regimes on resident Brook Trout populations downstream from a 15-MW dam used for hydropeaking, compared to a population in a nearby naturally flowing river. Length-at-age as determined by otolith back-calculations was higher in the regulated river relative to the naturally flowing river. Muscle tissue caloric content and weight–length relationships did not differ between rivers. Field metabolism, as inferred from fish otolith δ13C values, was higher in the regulated river relative to the naturally flowing river and was significantly positively related to time spent hydropeaking. Higher metabolic outputs in the regulated river were likely offset by an increased food supply, allowing for higher Brook Trout length-at-age. The opposing and complicated impacts of river regulation on Brook Trout highlight the need for studies to consider multiple indicators of fish health when characterising the response of fish populations to river regulation.
Schlagworte: carbon , nitrogen , ecol , elem

Oxygen isotope fractionation between bird eggshell calcite and body water: application to fossil eggs from Lanzarote (Canary Islands)
The Science of Nature (2016)
Nicolas Lazzerini, Christophe Lécuyer, Romain Amiot, Delphine Angst, Eric Buffetaut, François Fourel, Valérie Daux, Juan Francisco Betancort, Jean-Pierre Flandrois, Antonio Sánchez Marco, Alejandro Lomoschitz

Oxygen and carbon isotope compositions of fossil bird eggshell calcite (δ18Ocalc and δ13Ccalc) are regularly used to reconstruct paleoenvironmental conditions. However, the interpretation of δ18Ocalc values of fossil eggshells has been limited to qualitative variations in local climatic conditions as oxygen isotope fractionations between calcite, body fluids, and drinking water have not been determined yet. For this purpose, eggshell, albumen water, and drinking water of extant birds have been analyzed for their oxygen and carbon isotope compositions. Relative enrichments in 18O relative to 16O between body fluids and drinking water of +1.6 ± 0.9 ‰ for semi-aquatic birds and of +4.4 ± 1.9 ‰ for terrestrial birds are observed. Surprisingly, no significant dependence to body temperature on the oxygen isotope fractionation between eggshell calcite and body fluids is observed, suggesting that bird eggshells precipitate out of equilibrium. Two empirical equations relating the δ18Ocalc value of eggshell calcite to the δ18Ow value of ingested water have been established for terrestrial and semi-aquatic birds. These equations have been applied to fossil eggshells from Lanzarote in order to infer the ecologies of the Pleistocene marine bird Puffinus sp. and of the enigmatic giant birds from the Pliocene. Both δ13Ccalc and δ18Ocalc values of Puffinus eggshells point to a semi-aquatic marine bird ingesting mostly seawater, whereas low δ13Ccalc and high δ18Ocalc values of eggshells from the Pliocene giant bird suggest a terrestrial lifestyle. This set of equations can help to quantitatively estimate the origin of waters ingested by extinct birds as well as to infer either local environmental or climatic conditions.
Schlagworte: carbon , oxygen , ecol , mulitcarb

Trophic interactions between two neustonic organisms: insights from Bayesian stable isotope data analysis tools
Belg. J. Zool (2016)
Gilles Lepoint, Laurent Bernard, Sylvie Gobert, Loïc N Michel

The by-the-wind sailor Velella velella (Linnaeus, 1758) and its predator, the violet snail Janthina globosa (Swainson, 1822) are both floating neustonic organisms. Despite their global oceanic distribution and widespread blooms of V. velella in recent years, many gaps remain in our understanding about prey/predator interactions between these two taxa. Using stable isotope ratios of carbon and nitrogen, we aimed to study the trophic relationship between V. velella and J. globosa and investigate diet variation of V. velella and J. globosa in relation to individuals' size. Bayesian approaches were used to calculate isotopic niche metrics and the contribution of V. velella to the J. globosa diet. Our data showed that the isotopic niche of V. velella differed markedly from that of J. globosa. It was larger and did not overlap that of the J. globosa, indicating a more variable diet but at a lower trophic level than J. globosa. The isotopic niche of V. velella also varied according to the size class of the individual. Small individuals showed a larger isotopic niche than larger animals and low overlap with those of the larger individuals. J. globosa displayed very low isotopic variability and very small isotopic niches. In contrast, there were no isotopic composition nor isotopic niche differences between J. globosa of any size. This very low isotopic variability suggested that J. globosa is a specialist predator, feeding, at least in this aggregation, principally on V. velella. Moreover, outputs of a stable isotope mixing model revealed preferential feeding on medium to large (> 500 mm 2) V. velella colonies. While our isotopic data showed the trophic relationship between V. velella and J. globosa, many questions remain about the ecology of these two organisms, demonstrating the need for more fundamental studies about neustonic ecosystems.

Ecosystem metabolism and greenhouse gas production in a mesotrophic northern temperate lake experiencing seasonal hypoxia
Biogeochemistry (2016)
Kateri R. Salk, Peggy H. Ostrom, Bopaiah A. Biddanda, Anthony D. Weinke, Scott T. Kendall, Nathaniel E. Ostrom

Many lacustrine systems, despite management efforts to control eutrophication, are hypoxic during stratified periods. Hypoxia is a major concern, not only for its impact on aquatic life but also for its potential to stimulate production of the greenhouse gases, methane (CH4) and nitrous oxide (N2O). We investigated the drivers of hypoxia in Muskegon Lake, a temperate dimictic freshwater estuary that experiences frequent hypolimnetic mixing due to atmospheric forces, riverine inputs, and intrusion of oxic water from coastal upwelling in Lake Michigan. Primary production and respiration (R) rates obtained from a δ18O mass balance model were similar to other mesotrophic environments (0.56–26.31 and 0.57–13.15 mmol O2 m−3 day−1, respectively), although high P/R (≥2 in mid-summer) indicated there is sufficient autochthonous production to support hypoxia development and persistence. The isotopic enrichment factor for respiration (εobs) varied markedly and was least negative in August of both sampling years, consistent with high R rates. Hypoxic conditions were associated with accumulation of N2O but not CH4, and emissions of N2O are among the highest reported from lakes. The average N2O site preference value of 25.4‰ indicates that the majority of N2O was produced by nitrification via hydroxylamine oxidation, despite the presence of resilient hypoxia. While it has been hypothesized that denitrification acts as a sink for N2O in hypoxic lakes, it is clear that Muskegon Lake functions as a strong source of N2O via nitrification. Further considerations of lakes as global sources of N2O thus warrant a closer evaluation of nitrification-fueled N2O production.
Schlagworte: nitrogen , oxygen , ecol , gashead

Using hydrogen isotopes of freshwater fish tissue as a tracer of provenance
Ecology and Evolution (2016)
David X. Soto, Keith A. Hobson, Leonard I. Wassenaar

Hydrogen isotope (δ2H) measurements of consumer tissues in aquatic food webs are useful tracers of diet and provenance and may be combined with δ13C and δ15N analyses to evaluate complex trophic relationships in aquatic systems. However, δ2H measurements of organic tissues are complicated by analytical issues (e.g., H exchangeability, lack of matrix-equivalent calibration standards, and lipid effects) and physiological mechanisms, such as H isotopic exchange with ambient water during protein synthesis and the influence of metabolic water. In this study, δ2H (and δ15N) values were obtained from fish muscle samples from Lake Winnipeg, Canada, 2007–2010, and were assessed for the effects of species, feeding habits, and ambient water δ2H values. After lipid removal, we used comparative equilibration to calibrate muscle δ2H values to nonexchangeable δ2H equivalents and controlled for H isotopic exchange between sample and laboratory ambient water vapor. We then examined the data for evidence of trophic δ2H enrichment by comparing δ2H values with δ15N values. Our results showed a significant logarithmic correlation between fork length and δ2H values, and no strong relationships between δ15N and δ2H. This suggests the so-called apparent trophic compounding effect and the influence of metabolic water into tissue H were the potential mechanisms for δ2H enrichment. We evaluated the importance of water in controlling δ2H values of fish tissues and, consequently, the potential of H isotopes as a tracer of provenance by taking account of confounding variables such as body size and trophic effects. The δ2H values of fish appear to be a good tracer for tracking provenance, and we present a protocol for the use of H isotopes in aquatic ecosystems, which should be applicable to a broad range of marine and freshwater fish species. We advise assessing size effects or working with fish of relatively similar mass when inferring fish movements using δ2H measurements.
Schlagworte: hydrogen , ecol , elem

Lake Ontario salmon (Salmo salar) were not migratory: A long-standing historical debate solved through stable isotope analysis
Scientific Reports (2016)
Eric J. Guiry, Suzanne Needs-Howarth, Kevin D. Friedland, Alicia L. Hawkins, Paul Szpak, Rebecca Macdonald, Michelle Courtemanche, Erling Holm, Michael P. Richards, J. B. Petersen, N. D. Hamilton, J. M. Adovasio, A. L. McPherron, F. L. Stewart, D. R. Yesn

Lake Ontario once supported a large complex of Atlantic Salmon (Salmo salar) populations that became extinct prior to scientific study. Since the 1860s, research efforts to conserve and reintroduce a sustainable population of Atlantic Salmon have focused on determining whether Lake Ontario’s original salmon populations had migrated to the Atlantic Ocean as part of their lifecycle (anadromy), stayed in the lake year-round (potamodromy), or both. We used stable carbon, nitrogen, and sulfur isotope analyses of archaeological bones and historical museum-archived salmon scales to show that the original salmon populations from Lake Ontario completed their entire lifecycle without migrating to the Atlantic Ocean. With a time depth of more than 500 years, our findings provide a unique baseline with significant potential for informing modern restocking and conservation efforts.
Schlagworte: carbon , nitrogen , sulfur , ecol , elem

Trophic specializations of damselfishes are tightly associated with reef habitats and social behaviours
Marine Biology (2016)
Laura Gajdzik, Eric Parmentier, Nicolas Sturaro, Bruno Frédérich

Despite the increasing need to understand factors shaping community assembly, few studies have simultaneously explored the influence of niche-based and phylogenetic processes. Here, we investigate the relationships between diet, habitat and social behaviour in damselfishes (Pomacentridae) collected in 2014 at Moorea Island (17°30′S, 149°50′W), French Polynesia. Isotope ratios of carbon and nitrogen, in association with stomach contents, delineate three trophic groups: pelagic feeders consuming zooplankton, benthic feeders mainly grazing on algae and an intermediate group feeding on prey from the whole bentho-pelagic compartment. Sulphur isotope ratios indicate segregation between species of the outer reef mostly depending on oceanic input of zooplankton and the lagoonal species relying on locally produced resources or even on terrestrial supply. We demonstrate a tight association between dietary specializations, habitat characteristics and social behaviours, and these correlations are further confirmed by integrating the phylogeny of Pomacentridae. We also provide evidence of phylogenetic conservatism for the stomach content and the habitat–behaviour characters. However, the isotopic trait is evolutionarily more labile probably because it thoroughly depicts the ecological niche of species. To summarize, pelagic feeders (mainly from the Chrominae) usually form shoals in areas close to the open ocean at a maximum depth of 20 m. Benthic feeders (well represented in the Stegastinae) are ubiquitous, solitary and mostly territorial species found at various depths. The intermediate group includes gregarious species from three subfamilies that forage in the lagoon usually above 12 m depth. Overall, we give insight into processes that have structured the damselfish community in Moorea.
Schlagworte: carbon , nitrogen , sulfur , ecol , elem

Stable isotopes in deep-sea living (stained) foraminifera from the Mozambique Channel (eastern Africa): multispecies signatures and paleoenvironmental application
Journal of Oceanography (2016)
Christophe Fontanier, Saburo Sakai, Takashi Toyofuku, Eline Garnier, Christophe Brandily, Thibaut Eugene, Bruno Deflandre

Oxygen and carbon isotopes (δ18O and δ13C) have been investigated in carbonate tests of deep-sea foraminifera living in the Mozambique Channel (eastern Africa) to understand how environmental constraints (e.g., organic matter, oxygenation) control the intra- and interspecific variability of isotopic signatures. 197 living individuals, including eight different species, from various microhabitats within the sediment were sorted from sediment samples gathered at two stations on the Malagasy upper slope. Results show that the δ18O values of foraminiferal taxa were not controlled by microhabitat pattern. They presented tremendous and intriguing intraspecific variability that is not explained by the classical ontogenetic effect. The δ13C values of infaunal foraminiferal taxa do not show a 1:1 relationship with the bottom water δ13C DIC and do not present a constant offset from it; instead, they appear to be mainly controlled by a microhabitat effect. The lower δ13C values of shallow, intermediate, and deep infaunal taxa at the deeper station compared to those seen at the shallower station reflect the enhanced exportation of sedimentary organic matter at the sediment–water interface, and its related mineralization within the upper sediments. The ∆δ13C between shallow/very shallow infaunal species (i.e., Hoeglundina elegans, Uvigerina hispida) and intermediate/deep infaunal species (i.e., Melonis barleeanus, Globobulimina barbata) permits insight into (1) the exportation of organic matter to the seafloor and (2) the various degradation pathways for organic detritus in the benthic environments off NW Madagascar.
Schlagworte: carbon , oxygen , ecol , ocea , mulitcarb