Where are the decomposers? Uncovering the soil food web of a tropical montane rain forest in southern Ecuador using stable isotopes (15N)

2005 ◽  
Vol 21 (5) ◽  
pp. 589-593 ◽  
Author(s):  
Jens Illig ◽  
Reinhard Langel ◽  
Roy A. Norton ◽  
Stefan Scheu ◽  
Mark Maraun
Keyword(s):  
Food Webs ◽  
Animal Species ◽  
Nutrient Status ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
Montane Rain Forest ◽  
Large Numbers ◽  
Southern Ecuador ◽  
Aquatic Food ◽  
Taxonomic Affiliation

Trophic relationships among animals, plants and microflora are the basis for the construction of terrestrial and aquatic food webs, but both the structure and dynamics of food webs remain contentious. Examples of issues include how the overall nutrient status of a system affects the number of trophic levels, whether trophic-level omnivory and intraguild predation are rare or important, if different animal species can be aggregated into functional groups according to their taxonomic affiliation, how large numbers of decomposer animal species can coexist and why there are so many parthenogenetic taxa in soil.

scholarly journals Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pianpian Wu ◽  
Martin J. Kainz ◽  
Fernando Valdés ◽  
Siwen Zheng ◽  
Katharina Winter ◽  
...  
Keyword(s):  
Climate Change ◽  
Fatty Acids ◽  
Organic Matter ◽  
Food Webs ◽  
Essential Fatty Acids ◽  
Trophic Levels ◽  
Climate Change Scenarios ◽  
Essential Nutrients ◽  
Aquatic Food Webs ◽  
Aquatic Food

AbstractClimate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 μm) and larger sized plankton (microplankton; 40–200 μm), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.

scholarly journals ‘Taking Fishers’ Knowledge to the Lab’: An Interdisciplinary Approach to Understand Fish Trophic Relationships in the Brazilian Amazon

2021 ◽  
Vol 9 ◽  
Author(s):  
Paula Evelyn Rubira Pereyra ◽  
Gustavo Hallwass ◽  
Mark Poesch ◽  
Renato Azevedo Matias Silvano
Keyword(s):  
Stable Isotopes ◽  
Food Webs ◽  
Fish Species ◽  
Trophic Interactions ◽  
Brazilian Amazon ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
Ecological Knowledge ◽  
Data Limitations ◽  
Combining Data

Trophic levels can be applied to describe the ecological role of organisms in food webs and assess changes in ecosystems. Stable isotopes analysis can assist in the understanding of trophic interactions and use of food resources by aquatic organisms. The local ecological knowledge (LEK) of fishers can be an alternative to advance understanding about fish trophic interactions and to construct aquatic food webs, especially in regions lacking research capacity. The objectives of this study are: to calculate the trophic levels of six fish species important to fishing by combining data from stable isotopes analysis and fishers’ LEK in two clear water rivers (Tapajós and Tocantins) in the Brazilian Amazon; to compare the trophic levels of these fish between the two methods (stable isotopes analysis and LEK) and the two rivers; and to develop diagrams representing the trophic webs of the main fish prey and predators based on fisher’s LEK. The fish species studied were Pescada (Plagioscion squamosissimus), Tucunaré (Cichla pinima), Piranha (Serrasalmus rhombeus), Aracu (Leporinus fasciatus), Charuto (Hemiodus unimaculatus), and Jaraqui (Semaprochilodus spp.). A total of 98 interviews and 63 samples for stable isotopes analysis were carried out in both rivers. The average fish trophic levels did not differ between the stable isotopes analysis and the LEK in the Tapajós, nor in the Tocantins Rivers. The overall trophic level of the studied fish species obtained through the LEK did not differ from data obtained through the stable isotopes analysis in both rivers, except for the Aracu in the Tapajós River. The main food items consumed by the fish according to fishers’ LEK did agree with fish diets as described in the biological literature. Fishers provided useful information on fish predators and feeding habits of endangered species, such as river dolphin and river otter. Collaboration with fishers through LEK studies can be a viable approach to produce reliable data on fish trophic ecology to improve fisheries management and species conservation in tropical freshwater environments and other regions with data limitations.

scholarly journals Selenium Interactions with Algae: Chemical Processes at Biological Uptake Sites, Bioaccumulation, and Intracellular Metabolism

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 528 ◽  
Author(s):  
Dominic E. Ponton ◽  
Stephanie D. Graves ◽  
Claude Fortin ◽  
David Janz ◽  
Marc Amyot ◽  
...  
Keyword(s):  
Food Webs ◽  
Mechanistic Model ◽  
Trophic Levels ◽  
Primary Producers ◽  
Organic Selenium ◽  
Selenium Uptake ◽  
Aquatic Food Webs ◽  
Uptake Sites ◽  
Aquatic Food ◽  
Lentic Systems

Selenium (Se) uptake by primary producers is the most variable and important step in determining Se concentrations at higher trophic levels in aquatic food webs. We gathered data available about the Se bioaccumulation at the base of aquatic food webs and analyzed its relationship with Se concentrations in water. This important dataset was separated into lotic and lentic systems to provide a reliable model to estimate Se in primary producers from aqueous exposure. We observed that lentic systems had higher organic selenium and selenite concentrations than in lotic systems and selenate concentrations were higher in lotic environments. Selenium uptake by algae is mostly driven by Se concentrations, speciation and competition with other anions, and is as well influenced by pH. Based on Se species uptake by algae in the laboratory, we proposed an accurate mechanistic model of competition between sulfate and inorganic Se species at algal uptake sites. Intracellular Se transformations and incorporation into selenoproteins as well as the mechanisms through which Se can induce toxicity in algae has also been reviewed. We provided a new tool for risk assessment strategies to better predict accumulation in primary consumers and consequently to higher trophic levels, and we identified some research needs that could fill knowledge gaps.

scholarly journals Assessing plastic debris in aquatic food webs: what we know and don’t know about uptake and trophic transfer

2019 ◽  
Vol 27 (3) ◽  
pp. 304-317 ◽  
Author(s):  
J.F. Provencher ◽  
J. Ammendolia ◽  
C.M. Rochman ◽  
M.L. Mallory
Keyword(s):  
Food Webs ◽  
Trophic Transfer ◽  
Global Scale ◽  
Trophic Levels ◽  
Published Data ◽  
Plastic Pollution ◽  
Diverse Range ◽  
Global Environmental Issue ◽  
Freshwater Biota ◽  
Aquatic Food

Plastic pollution is now recognized as a global environmental issue that can affect the health of biota and ecosystems. Now that a growing number of species and taxa are known to ingest a diverse range of sizes and types of plastics and retain the plastics in their guts, there are increasing questions relating to the movement of plastics through food webs, and how biota may directly and indirectly ingest plastics. Here, we synthesize what is known from the published, peer-reviewed literature about plastic ingestion by animals and identify critical gaps in our knowledge. We systematically reviewed and examined the literature for studies that reported ingested plastics in marine and freshwater biota at a global scale. Our objective was to inform discussions and future studies regarding what we know about plastic ingestion and fate in food webs. We assessed what regions, ecosystems, and food webs have been studied to date and whether potential information may already be available to assess if trophic transfer of plastics may be occurring. We found 160 relevant publications through 2016. Most studies were concentrated in specific regions and in specific ecosystem types, with freshwater studies being the most limited. Moreover, most studies examined one species at a time with only a handful of regions with multiple taxa examined across multiple studies. Twenty-one percent of the regions have no published data on plastic ingestion to date. Although some studies have measured ingestion in multiple species across trophic levels, few have tested the hypothesis that plastics are transferred across trophic levels. Moreover, none have addressed questions related to biomagnification. While our review suggests that numerous papers have recorded the ingestion of plastics by biota across many trophic levels, habitats, and geographic regions, many questions regarding how or whether biota retain, bioaccumulate, biomagnify, and trophically transfer plastics still need to be addressed.

Understanding specifics in generalist diets of carnivorans by analyzing stable carbon isotope values in Pleistocene mammals of Florida

Paleobiology ◽  
10.1666/13055 ◽  
2014 ◽  
Vol 40 (3) ◽  
pp. 477-493 ◽  
Author(s):  
Robert S. Feranec ◽  
Larisa R. G. DeSantis
Keyword(s):  
Food Webs ◽  
Carbon Isotope ◽  
Prey Species ◽  
Tooth Enamel ◽  
Stable Carbon Isotope ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
Stable Carbon ◽  
Generalist Diet ◽  
Ancient Food

Within ancient ecosystems, it is generally difficult to determine the specific diets of species from higher trophic levels, which in turn hinders our understanding of trophic relationships and energy flow through these systems. To better understand the ecology of taxa at higher trophic levels, we used analysis of tooth enamel stable carbon isotope values to infer the dietary preferences of Canis edwardii and Smilodon gracilis from the Leisey Shell Pit 1A (LSP 1A) and Inglis 1A, two Pleistocene localities in Florida. The goals of the analyses were to (1) determine whether these carnivorans specialized in particular prey types or maintained a generalist diet; (2) ascertain whether carbon isotope values support what was previously suggested about the ecology of these species; and (3) establish what ecological details of ancient food webs can be discovered by carbon isotope analyses at higher trophic levels. Results show that the sampled carnivoran carbon isotope values are distributed among suspected prey isotope values, suggesting that varied prey were taken at the study localities. Prey compositions were modeled for each carnivoran species by using Stable Isotope Analysis in R (SIAR). The modeled diets indicate that each studied carnivoran had a generalist diet; however, there are differences in how these taxa achieved dietary generalization. At the glacial Inglis 1A locality, sampled individuals of C. edwardii and S. gracilis show similar isotope values and modeled dietary prey proportions, although both carnivorans do show a preference for grazing prey species. The similar isotopic values, and calculated prey proportions, observed between these species may imply greater interspecific competition for food. At the interglacial LSP 1A locality, C. edwardii shows values similar to those observed at Inglis 1A. In contrast, the data for S. gracilis shows a preference for consuming browsing prey species. Further, its restricted range of carbon isotope values suggests that S. gracilis may have concentrated its feeding within a particular habitat. Examination of stable carbon isotope values among species at higher trophic levels reveals that some intricacies of ancient food webs can be discerned.

scholarly journals Subsurface biogeochemistry is a missing link between ecology and hydrology in dam-impacted river corridors

2018 ◽  
Author(s):  
Emily B Graham ◽  
James C Stegen ◽  
Maoyi Huang ◽  
Xingyuan Chen ◽  
Timothy Scheibe
Keyword(s):  
Food Webs ◽  
Renewable Energy Sources ◽  
Trophic Levels ◽  
Surface Water Flow ◽  
Dam Impacts ◽  
Aquatic Food ◽  
Hydropower Impacts ◽  
Hydrologic Exchange ◽  
Induced Changes ◽  
River Corridor

Global investment in hydropower is rapidly increasing, fueled by a need to manage water availability and by incentives promoting renewable energy sources. This expansion poses unrecognized risks to the world’s vulnerable freshwaters. While many hydropower impacts have been investigated, dam-induced alterations to subsurface processes influence river corridor ecosystem health in ways that remain poorly understood. We advocate for a better understanding of dam impacts on subsurface biogeochemical activity, its connection to hydrology, and follow-on trophic cascades within the broader river corridor. We delineate an integrated view of hydropower impacts in which dam-induced changes to surface water flow regimes generate changes in surface-subsurface hydrologic exchange flows (HEFs) that subsequently (1) regulate resource availability for benthic microorganisms at the base of aquatic food webs and (2) impose kinetic constraints on biogeochemical reactions and organismal growth across a range of trophic levels. These HEF-driven effects on river corridor food webs, as mediated by subsurface biogeochemistry, are a key knowledge gap in our assessment of hydropower sustainability and putatively combine with other, more well-known dam impacts to result in significant changes to river corridor health. We suggest targeted laboratory and field-based studies to link hydrobiogeochemical models used to predict heat transport, biogeochemical rates, and hydrologic flow with ecological models that incorporate biomass changes in specific categories of organisms. Doing so will enable predictions of feedbacks among hydrology, temperature, biogeochemical rates, organismal abundances, and resource transfer across trophic levels. An understanding of dam impacts on subsurface hydrobiogeochemistry and its connection to the broader aquatic food web is fundamental to enabling mechanism-based decision making for sustainable hydropower operations.

Trophic relationships among animals associated with drifting wrack

2018 ◽  
Vol 69 (8) ◽  
pp. 1248 ◽  
Author(s):  
Ryan J. Baring ◽  
Rebecca E. Lester ◽  
Peter G. Fairweather
Keyword(s):  
Stable Isotope ◽  
Food Webs ◽  
Sandy Beach ◽  
Sandy Beaches ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
Gut Contents ◽  
Future Research ◽  
Δ13c And Δ15n ◽  
Trophic Pathways

Wrack accumulates commonly in surf zones of sandy beaches and can be a semipermanent feature. Very few studies have investigated the trophic pathways associated with wrack accumulations in sandy beach surf zones, despite their potential importance to nearshore food webs. In the present study, we were specifically interested in determining the fish–wrack trophic associations in the nearshore. Macrophytes, macroinvertebrates and fish were sampled from drifting wrack at two sites with different macrophyte compositions (i.e. algae v. an algae–seagrass mix) in South Australia. The gut contents of fish were sampled, and the δ13C and δ15N stable isotope signatures of fish, macroinvertebrates and macrophytes were analysed. Using both the stable isotope and diet data, we identified that fish are feeding among wrack accumulations, but some unexplained trophic pathways suggest that fish are also likely to be foraging over multiple habitats elsewhere for food. In contrast, there was more evidence that grazing macroinvertebrates may be feeding on and around macrophytes within the accumulations, as well as using them as habitat. Thus, the present study established some baseline trophic pathways associated with wrack accumulations in sandy beach surf zones. Given the modest evidence for use of wrack as a food source, the lower trophic levels of the food webs identified remain unknown and should be an area for future research.

scholarly journals Subsurface biogeochemistry is a missing link between ecology and hydrology in dam-impacted river corridors

2018 ◽  
Author(s):  
Emily B Graham ◽  
James C Stegen ◽  
Maoyi Huang ◽  
Xingyuan Chen ◽  
Timothy Scheibe
Keyword(s):  
Food Webs ◽  
Renewable Energy Sources ◽  
Trophic Levels ◽  
Surface Water Flow ◽  
Dam Impacts ◽  
Aquatic Food ◽  
Hydropower Impacts ◽  
Hydrologic Exchange ◽  
Induced Changes ◽  
River Corridor

Global investment in hydropower is rapidly increasing, fueled by a need to manage water availability and by incentives promoting renewable energy sources. This expansion poses unrecognized risks to the world’s vulnerable freshwaters. In particular, subsurface processes are altered by dam operations and may influence river corridor ecosystem health in ways that remain poorly understood. We advocate for a better understanding of dam impacts on subsurface biogeochemical activity, its connection to hydrology, and follow-on trophic cascades within the broader river corridor. We delineate an integrated view of hydropower impacts in which dam-induced changes to surface water flow regimes generate changes in surface-subsurface hydrologic exchange flows (HEFs) that subsequently (1) regulate resource availability for benthic microorganisms at the base of aquatic food webs and (2) impose kinetic constraints on biogeochemical reactions and organismal growth across a range of trophic levels. These HEF-driven effects on river corridor food webs, as mediated by subsurface biogeochemistry, are a key knowledge gap in our assessment of hydropower sustainability and putatively combine with other, more well-known dam impacts to result in significant changes to river corridor health. We suggest targeted laboratory and field-based studies to link hydrobiogeochemical models used to predict heat transport, biogeochemical rates, and hydrologic flow with ecological models that incorporate biomass changes in specific categories of organisms. Doing so will enable predictions of feedbacks among hydrology, temperature, biogeochemical rates, organismal abundances, and resource transfer across trophic levels. An understanding of dam impacts on subsurface hydrobiogeochemistry and its connection to the broader aquatic food web is fundamental to enabling mechanism-based decision making for sustainable hydropower operations.

scholarly journals Rapid scavenging of jellyfish carcasses reveals the importance of gelatinous material to deep-sea food webs

2014 ◽  
Vol 281 (1796) ◽  
pp. 20142210 ◽  
Author(s):  
Andrew K. Sweetman ◽  
Craig R. Smith ◽  
Trine Dale ◽  
Daniel O. B. Jones
Keyword(s):  
Energy Transfer ◽  
Food Webs ◽  
Deep Sea ◽  
Trophic Levels ◽  
Ne Atlantic ◽  
Large Numbers ◽  
Consumption Rates ◽  
Decapod Shrimp ◽  
Benthic Coupling ◽  
Scavenging Rates

Jellyfish blooms are common in many oceans, and anthropogenic changes appear to have increased their magnitude in some regions. Although mass falls of jellyfish carcasses have been observed recently at the deep seafloor, the dense necrophage aggregations and rapid consumption rates typical for vertebrate carrion have not been documented. This has led to a paradigm of limited energy transfer to higher trophic levels at jelly falls relative to vertebrate organic falls. We show from baited camera deployments in the Norwegian deep sea that dense aggregations of deep-sea scavengers (more than 1000 animals at peak densities) can rapidly form at jellyfish baits and consume entire jellyfish carcasses in 2.5 h. We also show that scavenging rates on jellyfish are not significantly different from fish carrion of similar mass, and reveal that scavenging communities typical for the NE Atlantic bathyal zone, including the Atlantic hagfish, galatheid crabs, decapod shrimp and lyssianasid amphipods, consume both types of carcasses. These rapid jellyfish carrion consumption rates suggest that the contribution of gelatinous material to organic fluxes may be seriously underestimated in some regions, because jelly falls may disappear much more rapidly than previously thought. Our results also demonstrate that the energy contained in gelatinous carrion can be efficiently incorporated into large numbers of deep-sea scavengers and food webs, lessening the expected impacts (e.g. smothering of the seafloor) of enhanced jellyfish production on deep-sea ecosystems and pelagic–benthic coupling.

Trophic ecology of a tropical aquatic and terrestrial food web: insights from stable isotopes (15N)

2006 ◽  
Vol 22 (4) ◽  
pp. 469-476 ◽  
Author(s):  
Alexander Kupfer ◽  
Reinhard Langel ◽  
Stefan Scheu ◽  
Werner Himstedt ◽  
Mark Maraun
Keyword(s):  
Food Web ◽  
Trophic Ecology ◽  
Isotope Analysis ◽  
Trophic Levels ◽  
Trophic Relationships ◽  
Isotopic Signatures ◽  
Top Predators ◽  
Aquatic Vertebrates ◽  
Aquatic Food ◽  
Litter Invertebrates

We used stable isotope analysis (15N/14N) to characterize the trophic relationships of consumer communities of an aquatic food web (a permanent pond) and the adjacent terrestrial food web (secondary dry dipterocarp forest) from a seasonal tropical field site in north-eastern Thailand. In general, isotopic signatures of aquatic vertebrates were higher (δ15N range = 4.51–9.90‰) than those of invertebrates (δ15N range = 1.10–6.00‰). High 15N signatures identified water snakes and swamp eels as top predators in the pond food web. In the terrestrial food web 15N signatures of saprophagous litter invertebrates (diplopods, earthworms), termites, ants and beetle larvae were lower than in those of predatory invertebrates (scolopendrids, scorpions, whip spiders). Predatory terrestrial frogs and caecilians had lower 15N signatures than snakes, indicating that snakes are among the top predators in the terrestrial web. Based on the distribution of isotopic signatures, we estimated five trophic levels for both the aquatic and terrestrial food web. The food chains of a seasonal tropical site studied were rather short, which implies similarities to the structure of temperate food webs.

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