Trophic Positions
    Animal Migration Patterns
    Soil Microbial Ecology


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.

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155 Ergebnisse:

Quantifying the ecological impact of invasive tunicates to shallow coastal water systems
Management of Biological Invasions (2016)
Phil Colarusso, Eric Nelson, Suzanne Ayvazian, Mary R Carman, Marty Chintala, Sinead Grabbert, David Grunden

Coastal ponds, due to their proximity to human activity, may be particularly vulnerable to invasions by non-native species. A number of invasive tunicate species have been documented in several of the coastal ponds on the island of Martha’s Vineyard, Massachusetts. Tunicates are voracious filter feeders, thus our study attempted to examine the impact of their feeding on the normal food web in a coastal pond. In 2012 and 2013, we sampled Stonewall (high tunicate abundance) and Lagoon Ponds (tunicates absent) on Martha’s Vineyard. We used quadrat sampling to quantify tunicate abundance, eelgrass shoot density and eelgrass canopy height. Fish, invertebrates and aquatic vegetation were collected via beach seine, minnow trap, crab traps or by hand. Water samples were run through a filter to collect phytoplankton. These biota samples were processed for carbon and nitrogen isotopic analysis. Temperature loggers were deployed in both ponds to collect water temperature. Detailed bathymetric readings were taken to generate an estimate of the volume of each pond. Tunicate filtration rates from published scientific literature, our volume estimate of Stonewall Pond and our measured tunicate abundance were used in a model to estimate the time needed by tunicates to filter a volume of water equal to Stonewall Pond. That time varied from less than an hour to over 17 hours. Isotopic analysis showed that tunicates were feeding on similar resources as the commercial shellfish species. There was broad overlap in the isotopic signatures between the biota from both ponds, suggesting that tunicates were not having a measurable impact to the food web. Tunicates exhibit significant seasonal abundance changes, with the peak occurring late summer into the early fall. The limited duration of this peak may not be sufficient to be reflected in the isotopic signature of resident biota. As water temperature continues to increase with climate change, the current assemblage of tunicates in these shallow water systems on Martha’s Vineyard will likely change in response. Key
Schlagworte: carbon , nitrogen , ecol , elem

Scaling the consequences of interactions between invaders from the individual to the population level
Ecology and Evolution (2016)
Blaine D. Griffen

The impact of human-induced stressors, such as invasive species, is often measured at the organismal level, but is much less commonly scaled up to the population level. Interactions with invasive species represent an increasingly common source of stressor in many habitats. However, due to the increasing abundance of invasive species around the globe, invasive species now commonly cause stresses not only for native species in invaded areas, but also for other invasive species. I examine the European green crab Carcinus maenas, an invasive species along the northeast coast of North America, which is known to be negatively impacted in this invaded region by interactions with the invasive Asian shore crab Hemigrapsus sanguineus. Asian shore crabs are known to negatively impact green crabs via two mechanisms: by directly preying on green crab juveniles and by indirectly reducing green crab fecundity via interference (and potentially exploitative) competition that alters green crab diets. I used life-table analyses to scale these two mechanistic stressors up to the population level in order to examine their relative impacts on green crab populations. I demonstrate that lost fecundity has larger impacts on per capita population growth rates, but that both predation and lost fecundity are capable of reducing population growth sufficiently to produce the declines in green crab populations that have been observed in areas where these two species overlap. By scaling up the impacts of one invader on a second invader, I have demonstrated that multiple documented interactions between these species are capable of having population-level impacts and that both may be contributing to the decline of European green crabs in their invaded range on the east coast of North America.

Zinc Isotope Ratios as Indicators of Diet and Trophic Level in Arctic Marine Mammals
Plos One (2016)
Klervia Jaouen, Paul Szpak, Michael P. Richards

Carbon and nitrogen stable isotope ratios of bone collagen are an established method for dietary reconstruction, but this method is limited by the protein preservation. Zinc (Zn) is found in bioapatite and the isotopic compositions of this element constitute a very promising dietary indicator. The extent of fractionation of Zn isotopes in marine environments, however, remains unknown. We report here on the measurement of zinc, carbon and nitrogen isotopes in 47 marine mammals from the archaeological site of Arvik in the Canadian Arctic. We undertook this study to test and demonstrate the utility of Zn isotopes in recent mammal bone minerals as a dietary indicator by comparing them to other isotopic dietary tracers. We found a correlation between δ66Zn values and trophic level for most species, with the exception of walruses, which may be caused by their large seasonal movements. δ6Zn values can therefore be used as a dietary indicator in marine ecosystems for both modern and recent mammals.
Schlagworte: carbon , nitrogen , ecol , elem

Characteristics of the infestation of Seriatopora corals by the coral gall crab Hapalocarcinus marsupialis Stimpson, 1859 on the great reef of toliara, Madagascar
Symbiosis (2016)
Lucas Terrana, Guillaume Caulier, Gildas Todinanahary, Gilles Lepoint, Igor Eeckhaut

This study describes the association between the obligatory symbiont coral gall crab Hapalocarcinus marsupialis and its stony coral hosts Seriatopora sp. within the Great Reef of Toliara in Madagascar and attempts to discuss their symbiotic status through comparison with previous studies. These corals are inhabited by crabs living in galls that can be categorised in four distinct morphological stages, where the first one corresponds to a small bud and the last one represents a completely closed gall surrounding the crab inside. Within the reef, 563 colonies of Seriatopora species were observed by scuba-diving at ten different stations: 37.8 % of them were infested by H. marsupialis, with a total of 763 galls, and with a majority of stage 4 galls. Galls are monopolised by females that can have different morphologies. Females store the sperm in two spermathecae and are fertilised when their morphology and size are similar to males and the gall is not closed. Histological observations coupled with scanning electronic microscopy analyses show that closed galls are made of an external living tissue, a mid skeletal layer and an internal living tissue. The internal living tissue includes polyps similar to the external tissue, some of them being sexually mature. Nitrogen and carbon isotopic signatures confirmed that these crabs are filter-feeders and do not feed on their host. This association perfectly highlights the difficulties to define the symbiotic status of a symbiont if one considers inflexible the three categories of symbiosis commonly defined.
Schlagworte: carbon , nitrogen , ecol , elem

Temporal Uncoupling between Energy Acquisition and Allocation to Reproduction in a Herbivorous-Detritivorous Fish.
PloS one (2016)
Francisco Villamarín, William E Magnusson, Timothy D Jardine, Dominic Valdez, Ryan Woods, Stuart E Bunn

Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ13C from reproductive and somatic tissues were correlated, probably because δ13C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ15N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.

Assessing the trophic position of two sharks from the open waters of the southeastern Pacific Ocean.
Latin American Journal of Aquatic Research (2016)
Sebastian A.; Cornejo Klarian

Stable isotope analyses for shortfin mako (Isurus oxyrinchus) and blue sharks (Prionace glauca) were conducted to assess their trophic position in two periods of time (before 1980 and after 2000) in the Southeastern Pacific waters (SEP). Both sharks showed that their trophic position decreased over time (P < 0.05). Many factors could be involved in this change such as dietary shifts, prey availability, or indirect fishing effects in SEP waters

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones.
PloS one (2016)
Sang Rul Park, Sangil Kim, Young Kyun Kim, Chang-Keun Kang, Kun-Seop Lee

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern-Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.

Impacts of Spartina alterniflora invasion on soil organic carbon and nitrogen pools sizes, stability, and turnover in a coastal salt marsh of eastern China
Ecological Engineering (2016)
Wen Yang, Shuqing An, Hui Zhao, Lingqian Xu, Yajun Qiao, Xiaoli Cheng

Plant invasion may impact ecosystem structure and function, and further affect soil organic matter (SOM) dynamics. However, the influence of plant invasion on soil organic carbon (C) and nitrogen (N) pools sizes, stability, and turnover in SOM of invaded ecosystems is not fully understood. In this study, soil C and N contents, and δ13C and δ15N values of free light fraction (LF), intra-aggregate particulate organic matter (iPOM) and mineral-associated organic matter (mSOM) were investigated in an invasive Spartina alterniflora community, adjacent bare flat and native Suaeda salsa and Phragmites australis communities. Short-term S. alterniflora invasion significantly enhanced organic C and N contents in SOM, free LF, iPOM, mSOM compared with bare flat and increased the proportion of allocated C in iPOM compared with S. salsa and P. australis soils (0–0.30m depth). The proportion of the S. alterniflora-derived C in free LF and iPOM were significantly higher than that in mSOM, and the highest S. alterniflora-derived C content was found in iPOM of S. alterniflora soil. The most enriched δ15N values were found in S. alterniflora soil. Increased δ15N values and decreased C:N ratios from the free LF to iPOM to mSOM in S. alterniflora soil indicated a greater degree of decomposition. The results suggest that 10-year S. alterniflora invasion significantly alters soil organic C and N pools sizes and stability through changing plant residuals input, physical distribution of S. alterniflora-derived C and C turnover in SOM fractions.
Schlagworte: carbon , nitrogen , soil , geol , ecol , elem

Morphological and Dietary Responses of Chipmunks to a Century of Climate Change.
Global change biology (2016)
Rachel E Walsh, Ana Paula A Assis, James L Patton, Gabriel Marroig, Todd E Dawson, Eileen A Lacey

Predicting how individual taxa will respond to climatic change is challenging, in part because the impacts of environmental conditions can vary markedly, even among closely related species. Studies of chipmunks (Tamias spp.) in Yosemite National Park provide an important opportunity to explore the reasons for this variation in response. While the alpine chipmunk (T. alpinus) has undergone a significant elevational range contraction over the past century, the congeneric and partially sympatric lodgepole chipmunk (T. speciosus) has not experienced an elevational range shift during this period. As a first step toward identifying the factors underlying this difference in response, we examined evidence for dietary changes and changes in cranial morphology in these species over the past century. Stable isotope analyses of fur samples from modern and historical museum specimens of these species collected at the same localities indicated that signatures of dietary change were more pronounced in T. alpinus, although diet breadth did not differ consistently between the study species. Morphometric analyses of crania from these specimens revealed significant changes in cranial shape for T. alpinus, with less pronounced changes in shape for T. speciosus; evidence of selection on skull morphology was detected for T. alpinus but not T. speciosus. These results are consistent with growing evidence that T. alpinus is generally more responsive to environmental change than T. speciosus but emphasize the complex and often geographically variable nature of such responses. Accordingly, future studies that make use of the taxonomically and spatially integrative approach employed here may prove particularly informative regarding relationships between environmental conditions, range changes, and patterns of phenotypic variation. This article is protected by copyright. All rights reserved.
Schlagworte: carbon , nitrogen , ecol , clim , elem

American woodcock migratory connectivity as indicated by hydrogen isotopes
The Journal of Wildlife Management (2016)
Daniel S. Sullins, Warren C. Conway, David A. Haukos, Keith A. Hobson, Leonard I. Wassenaar, Christopher E. Comer, I-Kuai Hung

To identify factors contributing to the long-term decline of American woodcock, a holistic understanding of range-wide population connectivity throughout the annual cycle is needed. We used band recovery data and isotopic composition of primary (P1) and secondary (S13) feathers to estimate population sources and connectivity among natal, early fall, and winter ranges of hunter-harvested juvenile American woodcock. We used P1 feathers from known-origin pre-fledged woodcock (n = 43) to create a hydrogen δ2Hf isoscape by regressing δ2Hf against expected growing-season precipitation (δ2Hp). Modeled δ2Hp values explained 79% of the variance in P1 δ2Hf values, indicating good model fit for estimating woodcock natal origins. However, a poor relationship (r2 = 0.23) between known-origin, S13 δ2Hf values, and expected δ2Hp values precluded assignment of early fall origins. We applied the δ2Hf isoscape to assign natal origins using P1 feathers from 494 hunter-harvested juvenile woodcock in the United States and Canada during 2010–2011 and 2011–2012 hunting seasons. Overall, 64% of all woodcock origins were assigned to the northernmost (>44°N) portion of both the Central and Eastern Management Regions. In the Eastern Region, assignments were more uniformly distributed along the Atlantic coast, whereas in the Central Region, most woodcock were assigned to origins within and north of the Great Lakes region. We compared our origin assignments to spatial coverage of the annual American woodcock Singing Ground Survey (SGS) and evaluated whether the survey effectively encompasses the entire breeding range. When we removed the inadequately surveyed Softwood shield Bird Conservation Region (BCR) from the northern portion of the SGS area, only 48% of juvenile woodcock originated in areas currently surveyed by the SGS. Of the individuals assigned to the northernmost portions of the breeding range, several were harvested in the southern extent of the wintering range. Based upon this latitudinal winter stratification, we examined whether woodcock employed a leapfrog migration strategy. Using δ2Hf values and band-recovery data, we found some support for this migration strategy hypothesis but not as a singular explanation. The large harvest derivation of individuals from the northernmost portions of the breeding range, and the difference in breeding distributions within each Management Region should be considered in future range-wide conservation and harvest management planning for American woodcock
Schlagworte: hydrogen , ecol , elem