TY - THES A1 - Guill, Christian T1 - Structure, stability and functioning of food webs T1 - Struktur, Stabilität und Funktion von Nahrungsnetzen N2 - In this thesis, a collection of studies is presented that advance research on complex food webs in several directions. Food webs, as the networks of predator-prey interactions in ecosystems, are responsible for distributing the resources every organism needs to stay alive. They are thus central to our understanding of the mechanisms that support biodiversity, which in the face of increasing severity of anthropogenic global change and accelerated species loss is of highest importance, not least for our own well-being. The studies in the first part of the thesis are concerned with general mechanisms that determine the structure and stability of food webs. It is shown how the allometric scaling of metabolic rates with the species' body masses supports their persistence in size-structured food webs (where predators are larger than their prey), and how this interacts with the adaptive adjustment of foraging efforts by consumer species to create stable food webs with a large number of coexisting species. The importance of the master trait body mass for structuring communities is further exemplified by demonstrating that the specific way the body masses of species engaging in empirically documented predator-prey interactions affect the predator's feeding rate dampens population oscillations, thereby helping both species to survive. In the first part of the thesis it is also shown that in order to understand certain phenomena of population dynamics, it may be necessary to not only take the interactions of a focal species with other species into account, but to also consider the internal structure of the population. This can refer for example to different abundances of age cohorts or developmental stages, or the way individuals of different age or stage interact with other species. Building on these general insights, the second part of the thesis is devoted to exploring the consequences of anthropogenic global change on the persistence of species. It is first shown that warming decreases diversity in size-structured food webs. This is due to starvation of large predators on higher trophic levels, which suffer from a mismatch between their respiration and ingestion rates when temperature increases. In host-parasitoid networks, which are not size-structured, warming does not have these negative effects, but eutrophication destabilises the systems by inducing detrimental population oscillations. In further studies, the effect of habitat change is addressed. On the level of individual patches, increasing isolation of habitat patches has a similar effect as warming, as it leads to decreasing diversity due to the extinction of predators on higher trophic levels. In this case it is caused by dispersal mortality of smaller and therefore less mobile species on lower trophic levels, meaning that an increasing fraction of their biomass production is lost to the inhospitable matrix surrounding the habitat patches as they become more isolated. It is further shown that increasing habitat isolation desynchronises population oscillations between the patches, which in itself helps species to persist by dampening fluctuations on the landscape level. However, this is counteracted by an increasing strength of local population oscillations fuelled by an indirect effect of dispersal mortality on the feeding interactions. Last, a study is presented that introduces a novel mechanism for supporting diversity in metacommunities. It builds on the self-organised formation of spatial biomass patterns in the landscape, which leads to the emergence of spatio-temporally varying selection pressures that keep local communities permanently out of equilibrium and force them to continuously adapt. Because this mechanism relies on the spatial extension of the metacommunity, it is also sensitive to habitat change. In the third part of the thesis, the consequences of biodiversity for the functioning of ecosystems are explored. The studies focus on standing stock biomass, biomass production, and trophic transfer efficiency as ecosystem functions. It is first shown that increasing the diversity of animal communities increases the total rate of intra-guild predation. However, the total biomass stock of the animal communities increases nevertheless, which also increases their exploitative pressure on the underlying plant communities. Despite this, the plant communities can maintain their standing stock biomass due to a shift of the body size spectra of both animal and plant communities towards larger species with a lower specific respiration rate. In another study it is further demonstrated that the generally positive relationship between diversity and the above mentioned ecosystem functions becomes steeper when not only the feeding interactions but also the numerous non-trophic interactions (like predator interference or competition for space) between the species of an ecosystem are taken into account. Finally, two studies are presented that demonstrate the power of functional diversity as explanatory variable. It is interpreted as the range spanned by functional traits of the species that determine their interactions. This approach allows to mechanistically understand how the ecosystem functioning of food webs with multiple trophic levels is affected by all parts of the food web and why a high functional diversity is required for efficient transportation of energy from primary producers to the top predators. The general discussion draws some synthesising conclusions, e.g. on the predictive power of ecosystem functioning to explain diversity, and provides an outlook on future research directions. N2 - In dieser Habilitationsschrift wird eine Zusammenstellung wissenschaftlicher Arbeiten präsentiert, die die Forschung zu komplexen Nahrungsnetzen in verschiedene Richtungen weiterentwickeln. Nahrungsnetze sind die Netzwerke der Räuber-Beute-Interaktionen in einem Ökosystem und bestimmen damit über die Verteilung der von allen Arten zum Überleben benötigten Ressourcen. Sie sind daher ein zentrales Konzept für das Verständnis der Mechanismen, die die Koexistenz einer Vielzahl von Arten ermöglichen. Angesichts der zunehmenden Intensität des anthropogenen globalen Wandels und sich weiter beschleunigendem Artensterben ist ein solches Verständnis von zentraler Bedeutung, nicht zuletzt auch für das menschliche Wohlergehen. Die Studien im ersten Teil der Thesis befassen sich mit generellen Mechanismen, die die Struktur und Stabilität von Nahrungsnetzen bestimmen. Es wird gezeigt, wie die allometrische Skalierung metabolischer Raten mit der Körpermasse der Individuen ihre Persistenz in größenstrukturierten Nahrungsnetzen unterstützt, und wie dies mit dem adaptiven Jagdverhalten von Räubern interagiert um stabile Nahrungsnetzstrukturen zu erzeugen. Basierend auf der Analyse empirisch dokumentierter Räuber-Beute-Paare wird zudem gezeigt, dass das Körpergrößenverhältnis von Räuber- und Beutearten deren Interaktionsstärke so beeinflusst, dass Populationsoszillationen stabilisiert werden. Weitere Studien demonstrieren, dass es zum Verständnis bestimmter populationsdynamischer Phänomene notwendig sein kann, die interne Struktur der betrachteten Populationen (z.B. die Größe von Alterskohorten) zu berücksichtigen. Auf diesen allgemeinen Erkenntnissen aufbauend werden im zweiten Teil der Habilitationsschrift Studien vorgestellt, die sich mit den Auswirkungen des anthropogenen globalen Wandels auf die Persistenz von Arten befassen. Erwärmung reduziert die Diversität in größenstrukturierten Nahrungsnetzen, indem sie zum Aussterben großer Räuberarten führt. Dies geschieht dadurch, dass die Respirationsrate wechselwarmer Tiere bei Erwärmung schneller ansteigt als ihre maximale Fraßrate. In Parasitoid-Wirt-Netzwerken mit flacher Größenstruktur hat Erwärmung keinen derartigen negativen Effekt, allerdings führt dort Eutrophierung durch die Induktion starker Populationsoszillationen zu Destabilisierung und Artensterben. In weiteren Studien werden die Auswirkungen von Habitatveränderung untersucht. Analog zur Erwärmung führt zunehmende Habitatisolation in den einzelnen Habitatflecken zu einem Rückgang der Diversität aufgrund des Aussterbens von großen Räuberarten. In diesem Fall wird das durch die Zunahme der Migrationsmortalität kleinerer und daher weniger mobiler Arten verursacht, welche dazu führt, dass ein immer größerer Anteil der Biomassenproduktion dieser Arten an die lebensfeindliche Matrix zwischen den Habitatflecken verloren geht. Es wird weiterhin gezeigt, dass zunehmende Isolation zur Desynchronisierung von Populationsoszillationen zwischen den einzelnen Habitatflecken führt. Allerdings führt die Zunahme der Wanderungsmortalität aufgrund eines indirekten Effektes auf die Fraßraten in den Habitatflecken zu einer Verstärkung der lokalen Populationsoszillationen, was den positiven Effekt der Desynchronisierung ausgleicht. Zuletzt wird in diesem Abschnitt ein neuartiger Mechanismus vorgestellt, der die Diversität in Meta-Gemeinschaften unterstützen kann. Er basiert auf selbstorganisierter Bildung räumlicher Muster in der Biomassenverteilung der Arten. Diese Muster erzeugen räumlich-zeitlich fluktuierende Selektionsdrücke, die die lokalen Artengemeinschaften in einem permanenten Nichtgleichgewichtszustand halten und dazu zwingen, sich ständig neu anzupassen. Da dieser Mechanismus auf der räumlichen Ausdehnung der Metagemeinschaften basiert, kann er ebenfalls empfindlich auf Habitatveränderungen reagieren. Im dritten Teil der Habilitationsschrift werden die Effekte von Biodiversität auf Ökosystemfunktionen untersucht. Die Studien beziehen sich dabei vor allem auf Bestand und Produktionsrate von Biomasse sowie auf die trophische Transfereffizienz. Es wird gezeigt, dass zunehmende Diversität von Tiergemeinschaften eine Verschiebung der Größenspektren von Pflanzen- und Tiergemeinschaften hin zu größeren Arten mit geringerer spezifischer Respirationsrate bewirkt, wodurch es den Pflanzengemeinschaften möglich wird, ihren Biomassenbestand trotz erhöhtem Fraßdruck zu erhalten. In einer weiteren Studie wird gezeigt, dass der im Allgemeinen positive Zusammenhang zwischen Biodiversität und den genannten Ökosystemfunktionen verstärkt wird, wenn neben den Fraßbeziehungen der Arten auch die zahlreichen weiteren Interaktionsmöglichkeiten der Arten (wie zum Beispiel Flächenkonkurrenz sessiler Arten) berücksichtigt werden. Abschließend werden zwei Studien präsentiert, auf funktioneller Diversität als zentraler erklärender Variable beruhen. Diese wird interpretiert als der Wertebereich, den funktionelle Merkmale, die die Interaktionen der Arten bestimmen, überspannen. Dieser Ansatz erlaubt es, mechanistisch nachzuvollziehen, wie die ökologischen Funktionen von Nahrungsnetzen von den einzelnen Teilen der Netzwerke beeinflusst werden, und warum eine hohe funktionelle Diversität für den effizienten Transport der Biomasse von den Primärproduzenten zu den Räubern an der Spitze der Nahrungskette notwendig ist. In der allgemeinen Diskussion werden einige zusammenfassende Schlussfolgerungen gezogen, die zum Beispiel die Vorhersagekraft von Ökosystemfunktionen zum Erklären der Diversität betreffen, und es wird ein Ausblick auf künftige Forschungsansätze gegeben. KW - ecology KW - food webs KW - biodiversity KW - anthropogenic global change KW - metacommunities KW - ecosystem functioning KW - functional diversity KW - Ökologie KW - Nahrungsnetze KW - Biodiversität KW - anthropogener globaler Wandel KW - Metagemeinschaften KW - Ökosystemfunktionen KW - funktionelle Diversität Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-561153 ER - TY - THES A1 - Ceulemans, Ruben T1 - Diversity effects on ecosystem functions of tritrophic food webs T1 - Diversität beeinflusst Ökosystemfunktionen tritrophischer Nahrungsnetze N2 - There is a general consensus that diverse ecological communities are better equipped to adapt to changes in their environment, but our understanding of the mechanisms by which they do so remains incomplete. Accurately predicting how the global biodiversity crisis affects the functioning of ecosystems, and the services they provide, requires extensive knowledge about these mechanisms. Mathematical models of food webs have been successful in uncovering many aspects of the link between diversity and ecosystem functioning in small food web modules, containing at most two adaptive trophic levels. Meaningful extrapolation of this understanding to the functioning of natural food webs remains difficult, due to the presence of complex interactions that are not always accurately captured by bitrophic descriptions of food webs. In this dissertation, we expand this approach to tritrophic food web models by including the third trophic level. Using a functional trait approach, coexistence of all species is ensured using fitness-balancing trade-offs. For example, the defense-growth trade-off implies that species may be defended against predation, but this defense comes at the cost of a lower maximal growth rate. In these food webs, the functional diversity on a given trophic level can be varied by modifying the trait differences between the species on that level. In the first project, we find that functional diversity promotes high biomass on the top level, which, in turn, leads to a reduction in the temporal variability due to compensatory dynamical patterns governed by the top level. Next, these results are generalized by investigating the average behavior of tritrophic food webs, for wide intervals of all parameters describing species interactions in the food web. We find that the diversity on the top level is most important for determining the biomass and temporal variability of all other trophic levels, and show how biomass is only transferred efficiently to the top level when diversity is high everywhere in the food web. In the third project, we compare the response of a simple food chain against a nutrient pulse perturbation, to that of a food web with diversity on every trophic level. By joint consideration of the resistance, resilience, and elasticity, we uncover that the response is efficiently buffered when biomass on the top level is high, which is facilitated by functional diversity on every trophic level in the food web. Finally, in the fourth project, we show that even in a simple consumer-resource model without any diversity, top-down control on the intermediate level frequently causes the phase difference between the intermediate and basal level to deviate from the quarter-cycle lag rule. By adding a top predator, we show that these deviations become even more likely, and anti-phase cycles are often observed. The combined results of these projects show how the properties of the top trophic level, including its functional diversity, have a decisive influence on the functioning of tritrophic food webs from a mechanistic perspective. Because top species are often among the most vulnerable to extinction, our results emphasize the importance of their conservation in ecosystem management and restoration strategies. N2 - Wissenschaftliche Erkenntnisse über die in natürlichen Ökoystemen beobachtete Artenvielfalt hat gezeigt, dass die Artenvielfalt fast überall auf der Erde rapide abnimmt. Dieser Rückgang ist hauptsächlich auf den zunehmenden menschlichen Einfluss auf die Umwelt zurückzuführen. Insbesondere die zunehmende Landnutzung z. B. für die Landwirtschaft, die Verschmutzung und die überfischung wirken sich negativ auf die Biodiversität aus. Den Einfluss von Biodiversität auf die Funktion von natürlichen Ökosystemen ist ein sehr aktives Forschungsgebiet der Ökologie. Insbesondere hat sich herausgestellt, dass die Biodiversität einen entscheidenden Einfluss auf wichtige Eigenschaften von Ökosystemen hat, wie z.B. die Menge an Biomasse, die sich etablieren kann, wie groß die Schwankungen der Biomasse im Laufe der Zeit sind, wie effizient Energie durch das gesamte Ökosystem übertragen wird und wie es auf Umweltstörungen reagiert. In dieser Dissertation wird der Zusammenhang zwischen Biodiversität und Ökosystemfunktionen mit Hilfe mathematischer Modelle von Nahrungsnetzen untersucht um mit Hilfe dieses Ansatz wichtige Eigenschaften und deren Relevanz zu ermitteln. Ein Nahrungsnetz beschreibt einen zentralen Teil dessen, wie Arten in einem Ökosystem miteinander interagieren, nämlich wer wen frisst. Unsere Modelle enthalten drei trophische Ebenen: eine basale Ebene (z.B. Pflanzen), die einer mittleren Ebene (Pflanzenfresser) als Nahrungsquelle dient, die wiederum von einer oberen Ebene (Fleischfresser) gefressen werden. Die Koexistenz mehrerer Arten auf einer trophischen Ebene ist über Trade-offs zwischen wichtigen Merkmalen der Arten sichergestellt. Ein Trade-off zwischen Fraßschutz und Wachstum bedeutet zum Beispiel, dass jeder Mechanismus, mit dem sich eine Art vor Fressfeinden schützen kann (z. B. die Bildung von Stacheln), mit einer geringeren Wachstumsrate erkauft wird (die Pflanze muss Energie für die Bildung der Stacheln aufgewendet werden). Auf diese Weise ist die Koexistenz mehrerer Arten möglich: kein Fraßschutz und eine hohe Wachstumsrate, gegenüber hohem Fraßschutz und einer niedrigen Wachstumsrate. Wir zeigen, dass die Eigenschaften der obersten trophischen Ebene, wie z. B. ihr Biomasseanteil und ihre Diversität, einen sehr großen Einfluss auf die Eigenschaften aller anderen trophischen Ebenen im Nahrungsnetz ausüben. Insbesondere beobachten wir, dass eine hohe Biomasse und Diversität auf der obersten trophischen Ebene zu einem Nahrungsnetz führt, das zeitlich stabiler ist, die verfügbaren anorganischen Nährstoffe besser ausnutzt und die erhöhte Produktivität der basalen trophischen Ebene effizienter an die Spitze des Nahrungsnetzes weitergibt. Darüber hinaus stellen wir fest, dass die oberste trophische Ebene eine Schlüsselrolle bei der Abschwächung von Auswirkungen auf ein Nahrungsnetz durch externe Störungen spielt. Zudem verstärkt sich dieser Effekt der obersten trophischen Ebene, wenn die anderen trophischen Ebenen ebenfalls eine hohe Diversität aufzeigen. Unsere Ergebnisse unterstreichen somit die Bedeutung von Diversität in allen Nahrungsnetzen, um einen Fortbestand von Ökosystemdienstleistungen zu gewährleisten, auf die wir angewiesen sind. KW - food webs KW - trait variation KW - trait diversity KW - Nahrungsnetze KW - Merkmalsvielfalt KW - Merkmalsvariation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-503259 ER - TY - JOUR A1 - Ryser, Remo A1 - Häussler, Johanna A1 - Stark, Markus A1 - Brose, Ulrich A1 - Rall, Björn C. A1 - Guill, Christian T1 - The biggest losers: habitat isolation deconsructs complex food webs from top to bottom JF - Proceedings of the Royal Society of London : B, Biological sciences N2 - Habitat fragmentation threatens global biodiversity. To date, there is only limited understanding of how the different aspects of habitat fragmentation (habitat loss, number of fragments and isolation) affect species diversity within complex ecological networks such as food webs. Here, we present a dynamic and spatially explicit food web model which integrates complex food web dynamics at the local scale and species-specific dispersal dynamics at the landscape scale, allowing us to study the interplay of local and spatial processes in metacommunities. We here explore how the number of habitat patches, i.e. the number of fragments, and an increase of habitat isolation affect the species diversity patterns of complex food webs (alpha-,beta-,gamma-, diversities). We specifically test whether there is a trophic dependency in the effect of these two factors on species diversity. In our model, habitat isolation is the main driver causing species loss and diversity decline. Our results emphasize that large-bodied consumer species at high trophic positions go extinct faster than smaller species at lower trophic levels, despite being superior dispersers that connect fragmented landscapes better. We attribute the loss of top species to a combined effect of higher biomass loss during dispersal with increasing habitat isolation in general, and the associated energy limitation in highly fragmented landscapes, preventing higher trophic levels to persist. To maintain trophic-complex and species-rich communities calls for effective conservation planning which considers the interdependence of trophic and spatial dynamics as well as the spatial context of a landscape and its energy availability. KW - food webs KW - allometry KW - bioenergetic model KW - metacommunity dynamics KW - dispersal mortality KW - landscape structure Y1 - 2019 U6 - https://doi.org/10.1098/rspb.2019.1177 SN - 0962-8452 SN - 1471-2954 VL - 286 IS - 1908 PB - Royal Society CY - London ER - TY - JOUR A1 - Colombo, Stefanie M. A1 - Wacker, Alexander A1 - Parrish, Christopher C. A1 - Kainz, Martin J. A1 - Arts, Michael T. T1 - A fundamental dichotomy in long-chain polyunsaturated fatty acid abundance between and within marine and terrestrial ecosystems JF - Environmental reviews = Dossiers environnement N2 - Polyunsaturated fatty acids (PUFA), especially long-chain (i.e., >= 20 carbons) polyunsaturated fatty acids (LC-PUFA), are fundamental to the health and survival of marine and terrestrial organisms. Therefore, it is imperative that we gain a better understanding of their origin, abundance, and transfer between and within these ecosystems. We evaluated the natural variation in PUFA distribution and abundance that exists between and within these ecosystems by amassing and analyzing, using multivariate and analysis of variance (ANOVA) methods, >3000 fatty acid (FA) profiles from marine and terrestrial organisms. There was a clear dichotomy in LC-PUFA abundance between organisms in marine and terrestrial ecosystems, mainly driven by the C-18 PUFA in terrestrial organisms and omega-3 (n-3) LC-PUFA in marine organisms. The PUFA content of an organism depended on both its biome (marine vs terrestrial) and taxonomic group. Within the marine biome, the PUFA content varied among taxonomic groups. PUFA content of marine organisms was dependent on both geographic zone (i.e., latitude, and thus broadly related to temperature) and trophic level (a function of diet). The contents of n-3 LC-PUFA were higher in polar and temperate marine organisms than those from the tropics. Therefore, we conclude that, on a per capita basis, high latitude marine organisms provide a disproportionately large global share of these essential nutrients to consumers, including terrestrial predators. Our analysis also hints at how climate change, and other anthropogenic stressors, might act to negatively impact the global distribution and abundance of n-3 LC-PUFA within marine ecosystems and on the terrestrial consumers that depend on these subsidies. KW - climate change KW - food webs KW - omega-3 KW - polyunsaturated fatty acids KW - trophic ecology Y1 - 2017 U6 - https://doi.org/10.1139/er-2016-0062 SN - 1208-6053 SN - 1181-8700 VL - 25 SP - 163 EP - 174 PB - NRC Research Press CY - Ottawa ER - TY - GEN A1 - Ceulemans, Ruben A1 - Gaedke, Ursula A1 - Klauschies, Toni A1 - Guill, Christian T1 - The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Diverse communities can adjust their trait composition to altered environmental conditions, which may strongly influence their dynamics. Previous studies of trait-based models mainly considered only one or two trophic levels, whereas most natural system are at least tritrophic. Therefore, we investigated how the addition of trait variation to each trophic level influences population and community dynamics in a tritrophic model. Examining the phase relationships between species of adjacent trophic levels informs about the strength of top-down or bottom-up control in non-steadystate situations. Phase relationships within a trophic level highlight compensatory dynamical patterns between functionally different species, which are responsible for dampening the community temporal variability. Furthermore, even without trait variation, our tritrophic model always exhibits regions with two alternative states with either weak or strong nutrient exploitation, and correspondingly low or high biomass production at the top level. However, adding trait variation increased the basin of attraction of the high-production state, and decreased the likelihood of a critical transition from the high- to the lowproduction state with no apparent early warning signals. Hence, our study shows that trait variation enhances resource use efficiency, production, stability, and resilience of entire food webs. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 744 KW - early-warning signals KW - top-down control KW - community ecology KW - regime shifts KW - food webs KW - compensatory dynamics KW - consumer diversity KW - metabolic theory KW - rapid evolution KW - stable states Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-435439 SN - 1866-8372 IS - 744 ER - TY - JOUR A1 - Ceulemans, Ruben A1 - Gaedke, Ursula A1 - Klauschies, Toni A1 - Guill, Christian T1 - The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system JF - Scientific Reports N2 - Diverse communities can adjust their trait composition to altered environmental conditions, which may strongly influence their dynamics. Previous studies of trait-based models mainly considered only one or two trophic levels, whereas most natural system are at least tritrophic. Therefore, we investigated how the addition of trait variation to each trophic level influences population and community dynamics in a tritrophic model. Examining the phase relationships between species of adjacent trophic levels informs about the strength of top-down or bottom-up control in non-steadystate situations. Phase relationships within a trophic level highlight compensatory dynamical patterns between functionally different species, which are responsible for dampening the community temporal variability. Furthermore, even without trait variation, our tritrophic model always exhibits regions with two alternative states with either weak or strong nutrient exploitation, and correspondingly low or high biomass production at the top level. However, adding trait variation increased the basin of attraction of the high-production state, and decreased the likelihood of a critical transition from the high- to the lowproduction state with no apparent early warning signals. Hence, our study shows that trait variation enhances resource use efficiency, production, stability, and resilience of entire food webs. KW - early-warning signals KW - top-down control KW - community ecology KW - regime shifts KW - food webs KW - compensatory dynamics KW - consumer diversity KW - metabolic theory KW - rapid evolution KW - stable states Y1 - 2019 U6 - https://doi.org/10.1038/s41598-019-43974-1 SN - 2045-2322 VL - 9 PB - Macmillan Publishers Limited CY - London ER - TY - JOUR A1 - Hixson, Stefanie M. A1 - Sharma, Bhanu A1 - Kainz, Martin J. A1 - Wacker, Alexander A1 - Arts, Michael T. T1 - Production, distribution, and abundance of long-chain omega-3 polyunsaturated fatty acids: a fundamental dichotomy between freshwater and terrestrial ecosystems JF - Environmental reviews = Dossiers environnement N2 - Long-chain polyunsaturated fatty acids (LC-PUFA) are critical for the health of aquatic and terrestrial organisms; therefore, understanding the production, distribution, and abundance of these compounds is imperative. Although the dynamics of LC-PUFA production and distribution in aquatic environments has been well documented, a systematic and comprehensive comparison to LC-PUFA in terrestrial environments has not been rigorously investigated. Here we use a data synthesis approach to compare and contrast fatty acid profiles of 369 aquatic and terrestrial organisms. Habitat and trophic level were interacting factors that determined the proportion of individual omega-3 (n-3) or omega-6 (n-6) PUFA in aquatic and terrestrial organisms. Higher total n-3 content compared with n-6 PUFA and a strong prevalence of the n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) characterized aquatic versus terrestrial organisms. Conversely, terrestrial organisms had higher linoleic acid (LNA) and alpha-linolenic acid (ALA) contents than aquatic organisms; however, the ratio of ALA: LNA was higher in aquatic organisms. The EPA + DHA content was higher in aquatic animals than terrestrial organisms, and increased from algae to invertebrates to vertebrates in the aquatic environment. An analysis of covariance (ANCOVA) revealed that fatty acid composition was highly dependent on the interaction between habitat and trophic level. We conclude that freshwater ecosystems provide an essential service through the production of n-3 LC-PUFA that are required to maintain the health of terrestrial organisms including humans. KW - aquatic ecosystems KW - conservation KW - eicosapentaenoic acid KW - docosahexaenoic acid KW - food webs Y1 - 2015 U6 - https://doi.org/10.1139/er-2015-0029 SN - 1208-6053 SN - 1181-8700 VL - 23 IS - 4 SP - 414 EP - 424 PB - NRC Research Press CY - Ottawa ER -