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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:

Trophic interactions among pelagic sharks and large predatory teleosts in the northeast central Pacific
Journal of Experimental Marine Biology and Ecology (2016)
Yunkai Li, Yuying Zhang, Xiaojie Dai

Sharks are considered to play important roles in structuring marine ecosystems, consequently understanding their trophic ecology and interactions with other marine predators is required. In the central Pacific Ocean, whether the trophic roles of pelagic sharks are complementary or redundant to large teleost predators remains unclear. In this study, stable carbon and nitrogen isotope analysis were used to examine the isotopic niche overlap of eight pelagic shark species and six pelagic teleost predators, including tuna and billfish. Large intra-specific variation and minimal inter-specific variation in both δ15N and δ13C values were observed among sharks and teleosts. Moreover, there was a high degree of trophic overlap among pelagic shark and teleost species, with the exception of the blue shark, the δ13C values of which indicated a much longer foraging time in the purely pelagic waters. Moreover, although the stable isotopic data suggested that the pelagic sharks in the study area share similar prey and habitats with other pelagic predators, such as tuna and billfish, blue sharks and shortfin mako sharks did not show isotopic overlap with these predators. These data highlight the diverse roles among pelagic sharks, supporting previous findings that this species complex is not trophically redundant; but further studies on the diet and fine-scale habitat used are required to verify this hypothesis.
Schlagworte: carbon , nitrogen , ecol , elem

Endangered Right Whales Enhance Primary Productivity in the Bay of Fundy
PLOS ONE (2016)
Joe Roman, John Nevins, Mark Altabet, Heather Koopman, James McCarthy, AR Longhurst, WG Harrison, JT Turner, TJ Lavery, B Roudnew, J Seymour, JM Mitchell, V Smetacek, S Nicol, J Roman, JJ McCarthy, S Nicol, A Bowie, S Jarman, D Lannuzel, KM Meiners, P van

Marine mammals have recently been documented as important facilitators of rapid and efficient nutrient recycling in coastal and offshore waters. Whales enhance phytoplankton nutrition by releasing fecal plumes near the surface after feeding and by migrating from highly productive, high-latitude feeding areas to low-latitude nutrient-poor calving areas. In this study, we measured NH4+ and PO43- release rates from the feces of North Atlantic right whales (Eubalaena glacialis), a highly endangered baleen whale. Samples for this species were primarily collected by locating aggregations of whales in surface-active groups (SAGs), which typically consist of a central female surrounded by males competing for sexual activity. When freshly collected feces were incubated in seawater, high initial rates of N release were generally observed, which decreased to near zero within 24 hours of sampling, a pattern that is consistent with the active role of gut microflora on fecal particles. We estimate that at least 10% of particulate N in whale feces becomes available as NH4+ within 24 hours of defecation. Phosphorous was also abundant in fecal samples: initial release rates of PO43- were higher than for NH4+, yielding low N/P nutrient ratios over the course of our experiments. The rate of PO43- release was thus more than sufficient to preclude the possibility that nitrogenous nutrients supplied by whales would lead to phytoplankton production limited by P availability. Phytoplankton growth experiments indicated that NH4+ released from whale feces enhance productivity, as would be expected, with no evidence that fecal metabolites suppress growth. Although North Atlantic right whales are currently rare (approximately 450 individuals), they once numbered about 14,000 and likely played a substantial role in recycling nutrients in areas where they gathered to feed and mate. Even though the NH4+ released from fresh whale fecal material is a small fraction of total whale fecal nitrogen, and recognizing the fact that the additional nitrogen released in whale urine would be difficult to measure in a field study, the results of this study support the idea that the distinctive isotopic signature of the released NH4+ could be used to provide a conservative estimate of the contribution of the whale pump to primary productivity in coastal regions where whales congregate.
Schlagworte: nitrogen , ecol , gashead

Ecosystem nitrogen fixation throughout the snow-free period in subarctic tundra: Effects of willow and birch litter addition and warming
Global Change Biology (2016)
Kathrin Rousk, Anders Michelsen

Nitrogen (N) fixation in moss-associated cyanobacteria is one of the main sources of available N for N-limited ecosystems like subarctic tundra. Yet, N2 fixation in mosses is strongly influenced by soil moisture and temperature. Thus, temporal scaling up of low frequency in situ measurements to several weeks, months or even the entire growing season without taking into account changes in abiotic conditions cannot capture the variation in moss-associated N2 fixation. We therefore aimed to estimate moss-associated N2 fixation throughout the snow-free period in subarctic tundra in field experiments simulating climate change: willow (Salix myrsinifolia) and birch (Betula pubescens spp. tortuosa) litter addition, and warming. To achieve this, we established relationships between measured in situ N2 fixation rates and soil moisture and soil temperature and used high-resolution measurements of soil moisture and soil temperature (hourly from May – October) to model N2 fixation. The modelled N2 fixation rates were highest in the warmed (2.8 ±0.3 kg N. ha-1) and birch litter addition plots (2.8 ±0.2 kg N ha-1), and lowest in the plots receiving willow litter (1.6 ±0.2 kg N ha-1). The control plots had intermediate rates (2.2 ±0.2 kg N ha-1). Further, N2 fixation was highest during the summer in the warmed plots, but was lowest in the litter addition plots during the same period. The temperature and moisture dependence of N2 fixation was different between the climate change treatments, indicating a shift in the N2 fixer community. Our findings, using a combined empirical and modelling approach, suggest that a longer snow-free period and increased temperatures in a future climate will likely lead to higher N2 fixation rates in mosses. Yet, the consequences of increased litter fall on moss-associated N2 fixation due to shrub expansion in the Arctic will depend on the shrub species’ litter traits.
Schlagworte: nitrogen , ecol , elem

Feeding patterns of two sympatric shark predators in coastal ecosystems of an oceanic island
Canadian Journal of Fisheries and Aquatic Sciences (2016)
Clément Trystram, Karyne Rogers, Marc Soria, Sébastien Jaquemet

Stomach contents and stable carbon and nitrogen isotope analyses (δ13C and δ15N) were used to investigate the trophic ecology of two apex predators, tiger sharks (Galeocerdo cuvier) and bull sharks (Carcharhinus leucas), from Reunion Island to describe their dietary habits at both the population and individual levels. In this oceanic island, the tiger and bull sharks were more piscivorous and teutophagous than noted in previous research from other localities. The δ13C values suggested that bull sharks depended on more neritic organic matter sources than tiger sharks, confirming a coastal habitat preference for bull sharks. Moreover, the total length of the bull shark influenced δ13C values, with smaller individuals being more coastal than larger individuals. All indicators suggest that there is a higher degree of similarity between individual tiger sharks compared with the more heterogeneous bull shark population, which is composed of individuals who specialize on different prey. These results suggest tha...
Schlagworte: carbon , nitrogen , ecol , ocea , elem

N/P imbalance as a key driver for the invasion of oligothrophic dune systems by a woody legume
Oikos (2016)
Florian Ulm, Christine Hellmann, Cristina Cruz, Cristina Máguas

Oligotrophic ecosystems, previously considered to be more resilient to invasive plants, are now recognised to be highly vulnerable to invasions. In these systems, woody legumes show belowground ecosystem engineering characteristics that enable invasion, however, the underlying processes are not well understood. Using a Portuguese primary dune ecosystem as an oligotrophic model system, belowground biomass pools, turnover rates and stoichiometry of a native (Stauracanthus spectabilis) and an invasive legume (Acacia longifolia) were compared and related to changes in the foliage of the surrounding native (Corema album) vegetation. We hypothesized that the invasive legume requires less phosphorus per unit of biomass produced and exhibits an enhanced nutrient turnover compared to the native vegetation, which could drive invasion by inducing a systemic N/P imbalance. Compared with the native legumes, A. longifolia plants had larger canopies, higher SOM levels and lower tissue P concentrations. These attributes were strongly related to legume influence as measured by increased foliar N content and less depleted δ15N signatures in the surrounding C. album vegetation. Furthermore, greater root and rhizosphere mass and increased nutrient turnover in the rhizosphere of the invader were associated with depleted foliar P in C. album. Our results emphasize that while A. longifolia itself maintains an efficient phosphorus use in biomass production, at the same time it exerts a strong impact on the N/P balance of the native system. Moreover, this study highlights the engineering of a belowground structure of roots and rhizosphere as a crucial driver for invasion, due to its central role in nutrient turnover. These findings provide new evidence that, under nutrient-limited conditions, considering co-limitation and nutrient cycling in oligotrophic systems is essential to understand the engineering character of invasive woody legumes.
Schlagworte: nitrogen , soil , ecol , elem

Can stable isotopes be used to infer site fidelity of nekton in open coastal areas?
Ecological Indicators (2016)
C. Vinagre, C. Madeira, M. Dias, L. Narciso, V. Mendonça

Stable isotope analysis has been applied to the investigation of movement in several species, including marine animals. However, its application to nekton living in open coastal areas is still very scarce. This study aims to test if stable isotope analysis can be used for this purpose over a much wider spatial scale than previously investigated. Stable isotope analysis was used to 1) investigate isotopic variation in shrimp and fish, in 11 sites, along a 160km coastal stretch, to 2) determine the site fidelity of the individuals within each species, and to 3) test the relation between the body size of the individuals within each species, at each site and the percentage of isotopic deviants. Site fidelity was the highest for the intertidal fish Gobius paganellus and Coryphoblennius galerita, with 60% and 64% of individuals considered residents, respectively, and lowest for the demersal fish Diplodus vulgaris and Diplodus sargus with 23% and 33% of resident individuals, respectively. The percentage of isotopic deviants was not correlated with length in any species. Site fidelity was considerably higher than that previously found for other open coastal areas and similar to more structured environments, like coastal ponds. It was hypothesized that the complex tri-dimensional structure of the rocky reefs that occur in this area, often encompassing channels and tide pools, offers conditions favourable to high site fidelity. This study shows that stable isotopes can be used to infer nekton movement in wide open coastal areas.
Schlagworte: carbon , nitrogen , ecol , elem

Soil organic carbon stocks in estuarine and marine mangrove ecosystems are driven by nutrient colimitation of P and N
Ecology and Evolution (2016)
Christian Weiss, Joanna Weiss, Jens Boy, Issi Iskandar, Robert Mikutta, Georg Guggenberger

Mangroves play an important role in carbon sequestration, but soil organic carbon (SOC) stocks differ between marine and estuarine mangroves, suggesting differing processes and drivers of SOC accumulation. Here, we compared undegraded and degraded marine and estuarine mangroves in a regional approach across the Indonesian archipelago for their SOC stocks and evaluated possible drivers imposed by nutrient limitations along the land-to-sea gradients. SOC stocks in natural marine mangroves (271–572 Mg ha−1 m−1) were much higher than under estuarine mangroves (100–315 Mg ha−1 m−1) with a further decrease caused by degradation to 80–132 Mg ha−1 m−1. Soils differed in C/N ratio (marine: 29–64; estuarine: 9–28), δ15N (marine: −0.6 to 0.7‰; estuarine: 2.5 to 7.2‰), and plant-available P (marine: 2.3–6.3 mg kg−1; estuarine: 0.16–1.8 mg kg−1). We found N and P supply of sea-oriented mangroves primarily met by dominating symbiotic N2 fixation from air and P import from sea, while mangroves on the landward gradient increasingly covered their demand in N and P from allochthonous sources and SOM recycling. Pioneer plants favored by degradation further increased nutrient recycling from soil resulting in smaller SOC stocks in the topsoil. These processes explained the differences in SOC stocks along the land-to-sea gradient in each mangrove type as well as the SOC stock differences observed between estuarine and marine mangrove ecosystems. This first large-scale evaluation of drivers of SOC stocks under mangroves thus suggests a continuum in mangrove functioning across scales and ecotypes and additionally provides viable proxies for carbon stock estimations in PES or REDD schemes.
Schlagworte: carbon , nitrogen , soil , ecol , elem

Nitrogen fixation by the reluctant diazotroph Cylindrospermopsis raciborskii (Cyanophyceae)
Journal of Phycology (2016)
Anusuya Willis, Ann W. Chuang, Michele A. Burford

Nitrogen fixation has been proposed as a mechanism that allows the diazotrophic cyanobacterium Cylindrospermopsis raciborskii to bloom in nitrogen-limited freshwater systems. However, it is unclear whether dinitrogen-fixation (N2-fixation) can supplement available dissolved inorganic nitrogen (DIN) for growth, or only provides minimum nitrogen (N) for cell maintenance under DIN deplete conditions. Additionally, the rate at which cells can switch between DIN use and N2-fixation is unknown. This study investigated N2-fixation under a range of nitrate concentrations. Cultures were grown with pre-treatments of nitrate replete (single dose 941 μmol NO3 ̅. L−1) and N-free conditions and then either received a single dose of 941 μmol NO3 ̅. L−1 (N941), 118 μmol. L−1 NO3 ̅ (N118) or 0 N. Heterocysts appeared from days 3 - 5 when treatments of high NO3 ̅ were transferred to N starvation media (N941:N0), and from day-5 in N941 transferred to N118 treatments. Conversely, transferring cells from N0 to N941 resulted in heterocysts being discarded from day-3 and day 5 for N0:N118. Heterocyst appearance correlated with a detectable rate of N2-fixation and up-regulation of nifH gene expression, the discard of heterocysts occurred after sequential reduction of nifH expression and N2-fixation. Nitrate uptake rates were not affected by pre-treatment, suggesting no regulation or saturation of this uptake pathway. These data demonstrate that for C. raciborskii, N2-fixation is regulated by the production or discard of heterocysts. In conclusion, this study has shown that N2-fixation only provides enough N to support relatively low growth under N-limited conditions, and does not supplement nitrate to increase growth rates.
Schlagworte: carbon , nitrogen , soil , ecol , elem

Can intercropping with the world's three major beverage plants help improve the water use of rubber trees?
Journal of Applied Ecology (2016)
Junen Wu, Wenjie Liu, Chunfeng Chen

1.The dramatic expansion of rubber plantations in mainland Southeast Asia and Southwest China has caused many eco-environmental problems, especially negative hydrological consequences. These problems have gradually worsened and pose formidable threats to rubber agriculture, especially in light of increasingly frequent extreme weather events. Although rubber-based agroforestry systems are regarded as the best solution for improving the sustainability of rubber agriculture and environmental conservation, plant water use and related interactions have rarely been examined in such systems. 2.We primarily used stable isotope (δD, δ18O, and δ13C) methods to test whether intercropping could improve the water use and extreme weather tolerance (extreme cold and drought in our study) of rubber trees in three types of promising agroforestry systems (i.e. rubber with tea, coffee, and cocoa) in Xishuangbanna, China. 3.We found that the rubber tree is a drought-avoidance plant with strong plasticity with respect to water uptake. This characteristic is reflected by its ability to cope with serious seasonal drought, allowing it to avoid interspecific competition for water. The rubber trees showed wasteful water behaviour unless they were intercropped with tea or coffee. However, these intercropped species exhibited drought-tolerance strategies and maintained lower water use efficiencies to strengthen their competitive capacity for surface soil water. The stable δ13C values of the intercrop leaves indicated that all the agroforestry systems have stable internal microclimatic environments or higher resistance. 4.Synthesis and applications. This study suggests that interspecific competition for water can enhance the water use efficiency of drought-avoidance plants (i.e. rubber trees) and lead to complementarity between the root distributions of plants in rubber agroforestry systems (i.e. rubber with tea, coffee, and cocoa). All agroforestry systems have higher resistance, but tea was the most suitable intercrop in terms of water use because the interspecific competition for water was moderate and the agroforestry system retained much more soil water and improved the water use efficiency of the rubber tree. Considering the root characteristics of the tea trees, we suggest that the crops selected for intercropping with rubber trees should have short lateral roots and a moderate amount of fine roots that overlap with the roots of the rubber trees in the shallow soil layer.
Schlagworte: carbon , nitrogen , soil , ecol , elem

Endangered Right Whales Enhance Primary Productivity in the Bay of Fundy
PLOS ONE (2016)
Joe Roman, John Nevins, Mark Altabet, Heather Koopman, James McCarthy, AR Longhurst, WG Harrison, JT Turner, TJ Lavery, B Roudnew, J Seymour, JM Mitchell, V Smetacek, S Nicol, J Roman, JJ McCarthy, S Nicol, A Bowie, S Jarman, D Lannuzel, KM Meiners, P van

Marine mammals have recently been documented as important facilitators of rapid and efficient nutrient recycling in coastal and offshore waters. Whales enhance phytoplankton nutrition by releasing fecal plumes near the surface after feeding and by migrating from highly productive, high-latitude feeding areas to low-latitude nutrient-poor calving areas. In this study, we measured NH4+ and PO43- release rates from the feces of North Atlantic right whales (Eubalaena glacialis), a highly endangered baleen whale. Samples for this species were primarily collected by locating aggregations of whales in surface-active groups (SAGs), which typically consist of a central female surrounded by males competing for sexual activity. When freshly collected feces were incubated in seawater, high initial rates of N release were generally observed, which decreased to near zero within 24 hours of sampling, a pattern that is consistent with the active role of gut microflora on fecal particles. We estimate that at least 10% of particulate N in whale feces becomes available as NH4+ within 24 hours of defecation. Phosphorous was also abundant in fecal samples: initial release rates of PO43- were higher than for NH4+, yielding low N/P nutrient ratios over the course of our experiments. The rate of PO43- release was thus more than sufficient to preclude the possibility that nitrogenous nutrients supplied by whales would lead to phytoplankton production limited by P availability. Phytoplankton growth experiments indicated that NH4+ released from whale feces enhance productivity, as would be expected, with no evidence that fecal metabolites suppress growth. Although North Atlantic right whales are currently rare (approximately 450 individuals), they once numbered about 14,000 and likely played a substantial role in recycling nutrients in areas where they gathered to feed and mate. Even though the NH4+ released from fresh whale fecal material is a small fraction of total whale fecal nitrogen, and recognizing the fact that the additional nitrogen released in whale urine would be difficult to measure in a field study, the results of this study support the idea that the distinctive isotopic signature of the released NH4+ could be used to provide a conservative estimate of the contribution of the whale pump to primary productivity in coastal regions where whales congregate.
Schlagworte: nitrogen , ecol , gashead