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Trophische Interaktionen in tropischen Waldfragmenten

In diesem Forschungsvorhaben sollen die Effekte von Habitatfragmentierung auf Nahrungsnetze untersucht werden. Als Modellsystem dient die trophische Kaskade 'Pflanze - Pilz/Blattschneiderameise - Prädator/Parasit' im Atlantischen Regenwald Brasiliens, eines der weltweit am stärksten gefährdeten Waldökosysteme. Seit langem wird eine Zunahme der Dichte und Diversität von Blattschneiderameisen (BSA) in gestörten Habitaten beobachtet. Die Gründe hierfür sind jedoch weitgehend ungeklärt. Die diesem Projekt zugrunde liegenden Arbeitshypothesen basieren auf der Annahme, dass sowohl die Kontrolle durch Resourcenqualität als auch durch Prädation und Parasitismus in fragmentierten Wäldern weniger effizient sind als in geschlossenen Waldsystemen. Zur Beurteilung der bottom-up-Kontrolle wird daher untersucht, ob (1) pflanzliche Abwehr, (2) BSA Nahrungsbreite, (3) -Aktionsradius und (4) -Herbivorierate in Waldfragmenten zunehmen. Die Effizienz der top-down Kontrolle wird darüber bestimmt ob (1) Prädationsrate sowie (2) Ameisen- und Pilzparasitierung in kontinuierlichen Wäldern zunehmen und (3) der Koloniegründungserfolg abnimmt. Die Evaluierung der einzelnen Parameter und ihrer relativen Bedeutung soll das Verständnis der funktionellen Rolle trophischer Interaktionen am Beispiel dieser Schlüsselarten neotropischer Ökosysteme verbessern

Light effects on the vertical positioning of the freshwater jellyfish (Craspedacusta sowerbii Lankester, 1880)

We experimentally manipulated the presence of light and light intensity (F = 36.7 μmol m⁻² s⁻¹; D = 0 μmol m⁻² s⁻¹; L = 4.8 μmol m⁻² s⁻¹; M = 21.4 μmol m⁻² s⁻¹) and tested their effects on the vertical positioning of the freshwater jellyfish (Craspedacusta sowerbii) medusae. For the experiments, approximately 100 C. sowerbii medusae were collected in August 2017 in two lakes (Haager Weiher and Leitner Weiher) in Bavaria, Germany. Testing was carried out at Seeon Limnological Station in close vicinity to the collection site. The experimental columns were 7.4 cm in diameter and 170 cm high and were marked with horizontal lines every 5 cm for visual position estimation. Four replicates run in parallel. One C. sowerbii medusa was used in each experimental column. Data cover three light treatments, each run twice: 1) 16:8 h full light (F)–dark (D) light intensity cycles (nF = 716, nD = 428), 2) 16:8 h full light (F)–full dark (D) light intensity cycles complemented with low (L) and medium (M) light intensities (nF = 96, nM = 96, nL = 48, nD = 288), and 3) altered light intensities in approximately 2-hour periods randomly among dark, low, medium, and full light intensities (nF = 96, nM = 76, nL = 72, nD = 336). Results show that light alone was sufficient to trigger a vertical position change of jellyfish towards the water surface, especially high light.

Forest soil fauna densities on group level, 2008

<p>Original data comes from a project which takes or took place as part of the DFG priority program "Exploratories for large-scale and long-term functional biodiversity research". The data is stored together with descriptive metadata, in combination called a dataset, in the project repository (https://www.bexis.uni-jena.de). Species information was extracted from that original dataset. The second paragraph is part of the metadata of the original dataset.</p><p>Changes in soil food web structure of the decomposer system with land use intensity in forest systems</p>

Bulk stable isotope analysis (SIA) of historical and contemporary squid beaks

Raw data obtained from stable isotope analysis of δ13C and δ15N in beaks of the squids Gonatus fabricii (Lichtenstein, 1818) and Todarodes sagittatus (Lamarck, 1798) (Cephalopoda: Oegopsida), and primary analyses of these data. Squids sampled in the Baffin Bay, Davis Strait and Nordic Seas (1882-2010) and Iceland, Faroe Islands and Ireland (1844-2023), respectively. The beaks either come from the squids caught as bycatch, or from natural history museums, from stomach contents of predators.

Amino acid isotope data of deep sea fauna, organic matter and sediment of a sponge ground on an Arctic North Atlantic seamount

Isotope data of deep sea fauna, organic matter and sediment of a sponge ground on an Arctic North Atlantic seamount

Sponge grounds are hotspots of biomass and biodiversity in the otherwise barren deep sea. It remains unknown how these ecosystems can thrive in such food limited environments, since organic matter settling from the surface ocean covers only small parts of their carbon demand. In this study, the food-web interactions and potential food sources of a North Atlantic deep-sea sponge reef were identified by bulk and compound-specific stable isotope analysis of amino and fatty acids. The elevated bulk δ15N values of sponges with relatively low abundance of associated microbes (LMA) is in line with a position at the top of the benthic food web, while the relatively high δ13C and intermediate δ15N values of high microbial abundance (HMA) sponges suggest considerable reliance on an alternate resource. Trophic positions based on amino acid δ15N values placed HMA sponges at the base of the food web. Fatty acid analysis of δ13C indicated transfer of sponge derived organic matter to the wider food web. Our results show that sponges drive both bottom-up and top-down processes, shunting organic carbon to higher trophic levels that would otherwise be inaccessible to other fauna. In this way, sponges are key to the sustenance of thriving deep-sea ecosystems.

Global compilation of stable carbon (δ13C) and nitrogen (δ15N) isotope values of meso- and bathypelagic fish

Stable isotope analysis (SIA) has emerged as a valuable tool for understanding the trophic structure of the marine food web and gaining insights into trophic levels and niche. Researchers are increasingly utilizing SIA in studies focused on feeding ecology, particularly in estimating the long-term diets of meso- and bathypelagic fish. To facilitate this research, a global database of published data on stable isotopes, specifically δ13C and δ15N, of meso- and bathypelagic fish was created. The database was constructed by conducting a thorough search on Google Scholar and reviewing the references cited in the retrieved papers. The search primarily involved using popular terms such as stable isotope analysis or feeding ecology in combination with mesopelagic or bathypelagic fish. The resulting SIA database contains δ13C and δ15N values for 95 different species of meso- and bathypelagic fish, belonging to 27 families, with specimens collected between 2004 and 2015. Each entry in the database includes information on the sampling location, month and year of sample collection, taxonomic classifications (phylum, class, order, family), number of samples analyzed, as well as the reference and DOI of the original data source. This global SIA database holds significant potential as a valuable tool and data source for conducting large-scale meta-analyses.

Bulk isotope data of deep sea fauna, organic matter and sediment of a sponge ground on an Arctic North Atlantic seamount

Food web on ice - investigation of the bioaccumulation of chemicals in an exemplary food chain

Um das Akkumulationsverhalten umweltrelevanter Chemikalien unter realen Bedingungen zu untersuchen, wurden in vielen verschiedenen aquatischen Ökosystemen weltweit trophische Magnifikationsfaktoren (TMFs) abgeleitet. Der TMF ist definiert als eine Metrik, die die durch schnittliche trophische Anreicherung einer Chemikalie durch das analysierte Nahrungsnetz unter realistischen Umweltbedingungen beschreibt. TMFs sind nicht nur für Fragen der Risiko bewertung von Chemikalien interessant, sondern auch für bestimmte Aspekte der Überwachung von Stoffen im Kontext der Wasserrahmenrichtlinie (WRRL). Diese Untersuchung ist die erste TMF-Studie, die in einem deutschen Süßwasser-Ökosystem - dem Templiner See bei Potsdam - durchgeführt wurde. Ziel der Studie war es, die Nahrungsnetzanreicherung von Stoffen zu unter suchen und zuverlässige TMFs abzuleiten, die für regulatorische Zwecke verwendet werden können. Es wurde ein Satz von Nahrungsnetzproben gewonnen, der 15 Biota-Proben aus etwa drei trophischen Ebenen umfasst. Die Proben wurden nach standardisierten Protokollen der Umweltprobenbank des Bundes (UPB) aufgearbeitet und tiefgekühlt gelagert. Die erhaltenen Nahrungsnetzproben bilden somit ein "Nahrungsnetz auf Eis" und sind nun für eine Vielzahl von Analysen einsetzbar. In einem ersten Schritt wurde eine Plausibilitätsprüfung durchgeführt. Als Vergleichsmaßstab dienen persistente organische Schadstoffe (POPs), von denen bekannt ist, dass sie sich in Nahrungsnetzen anreichern und zudem nicht leicht metabolisiert werden. Von den hier analysierten POPs zeigen die meisten Stoffe TMFs signifikant über 1. In wenigen Fällen ist zwar auch eine Anreicherung zu erkennen, die jedoch statistisch nicht signifikant ist. Da nicht nur POPs mit lipophilen Akkumulationseigenschaften analysiert wurden, kann der Schluss gezogen werden, dass die archivierten Proben des "Nahrungsnetzes auf Eis" aus dem Templiner See zur Charakterisierung des trophischen Magnifikationspotentials weiterer in den Proben vorhandener Substanzen mit weniger untersuchten Bioakkumulationseigenschaften verwendet werden können. Zu diesem Zweck wurden mehrere PFAS, Arzneimittelwirkstoffe, Pestizide und Methylsiloxane in den Proben analysiert, um für diese TMFs abzuleiten. Quelle: Forschungsbericht

Biodiversity in agroecosystems: a multi-trophic approach to metacommunities

The goal of the proposal is to explore the structure and functioning of metacommunities in ecological compensation areas at a multi-trophic level. First, we will assess the effect of plant diversity and herbivore and/or predator exclusion on metacommunity functioning in sown wildflower strips. We will document the communities inhabiting these experimental plots, paying attention at interactions between species, and with consideration of larger consumers linking these habitats with the surrounding matrix. Second, we will explore the relationship between various measures of the environment (isolation, habitat size) and descriptors of the metacommunities (diversity, composition, abundances, and productivity of various taxonomic groups, food-web structure, temporal variability, local invasions and extinctions). Third, using a high-quality dataset on quantitative food webs and the present data, we will conduct meta-analyses to test various models of community organisation (neutral models of biodiversity, species-area relationship in trophic levels, regional similarity hypothesis, food-web structure). Fourth, we will develop various models describing food-web structure and metacommunities dynamics. We will synthesize our results to develop a theory of 'meta food-webs'. Fifth, we will apply the gained knowledge to improve current agri-environment schemes. The study of species interactions in spatially structured metacommunities is comprehensive and global. As such, this project has a strong potential to provide fundamental insight into conservation biology. This project is multidisciplinary, putting together practitioners, ecologists and mathematicians, and is expected to yield important results both of fundamental and conservation relevance. We will use various methodologies to reach our goals. For the first part, we will set up an experiment with replicated sown wildflower strips where plant species richness and the abundance of major predators (foxes and birds of prey) and/or of major herbivores (voles and slugs) will be controlled (balanced incomplete block design). The other parts will rely on classical meta-analyses, multivariate statistics, and mathematical modelling. For the latter part, we will develop stochastic models to explore the dynamics of communities.

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