scholarly journals Trophic state changes can affect the importance of methane-derived carbon in aquatic food webs

2017 ◽  
Vol 284 (1857) ◽  
pp. 20170278 ◽  
Author(s):  
Jos Schilder ◽  
Maarten van Hardenbroek ◽  
Paul Bodelier ◽  
Emiliya P. Kirilova ◽  
Markus Leuenberger ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Nutrient Availability ◽  
Carbon Isotopic Composition ◽  
Algal Growth ◽  
Resting Eggs ◽  
Sediment Geochemistry ◽  
Strong Impact ◽  
Carbon Isotopic ◽  
Aquatic Food

Methane-derived carbon, incorporated by methane-oxidizing bacteria, has been identified as a significant source of carbon in food webs of many lakes. By measuring the stable carbon isotopic composition (δ 13 C values) of particulate organic matter, Chironomidae and Daphnia spp. and their resting eggs (ephippia), we show that methane-derived carbon presently plays a relevant role in the food web of hypertrophic Lake De Waay, The Netherlands. Sediment geochemistry, diatom analyses and δ 13 C measurements of chironomid and Daphnia remains in the lake sediments indicate that oligotrophication and re-eutrophication of the lake during the twentieth century had a strong impact on in-lake oxygen availability. This, in turn, influenced the relevance of methane-derived carbon in the diet of aquatic invertebrates. Our results show that, contrary to expectations, methane-derived relative to photosynthetically produced organic carbon became more relevant for at least some invertebrates during periods with higher nutrient availability for algal growth, indicating a proportionally higher use of methane-derived carbon in the lake's food web during peak eutrophication phases. Contributions of methane-derived carbon to the diet of the investigated invertebrates are estimated to have ranged from 0–11% during the phase with the lowest nutrient availability to 13–20% during the peak eutrophication phase.

scholarly journals Effects of experimental warming, litter species, and presence of macroinvertebrates on litter decomposition and associated decomposers in a temperate mountain stream

2015 ◽  
Vol 72 (2) ◽  
pp. 206-216 ◽  
Author(s):  
Verónica Ferreira ◽  
Eric Chauvet ◽  
Cristina Canhoto
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Litter Decomposition ◽  
Castanea Sativa ◽  
Mountain Stream ◽  
Ambient Temperatures ◽  
C Cycle ◽  
Detrital Food Web ◽  
Water Courses ◽  
Aquatic Food

Small woodland streams make the majority of water courses in most watersheds. Litter decomposition is a key ecosystem process in these shaded streams, and its response to warming can have profound consequences for food webs and the carbon (C) cycle. However, these responses can be modulated by litter identity and the structure of the detrital food web. Here we report on a manipulative study aiming at evaluating the effects of warming (+2.8 °C), litter identity (chestnut (Castanea sativa) or oak (Quercus robur) litter), and the structure of the detrital food web (presence or absence of macroinvertebrates) on litter decomposition and decomposers in a small, temperate woodland stream. Warming significantly stimulated overall (microbial- + macroinvertebrate-driven) decomposition of oak and microbial-driven decomposition of chestnut. The similar shredder densities at elevated and ambient temperatures suggest that stimulated overall decomposition of oak resulted from increased activity of macroinvertebrate individuals. Stimulated microbial-driven decomposition of chestnut resulted from higher fungal activity with warming. Stimulation of litter decomposition by warming can lead to increases in the amount of C returned to the atmosphere and to a faster disappearance of litter from the benthos, with consequences to the C cycle and aquatic food webs.

scholarly journals The effects of biomanipulation on the biogeochemistry, carbon isotopic composition and pelagic food web relations of a shallow turf lake

2005 ◽  
Vol 2 (4) ◽  
pp. 997-1031 ◽  
Author(s):  
B. M. Bontes ◽  
R. Pel ◽  
B. W. Ibelings ◽  
H. T. S. Boschker ◽  
J. J. Middelburg ◽  
...  
Keyword(s):  
Food Web ◽  
Green Algae ◽  
Cell Sorting ◽  
Carbon Isotopic Composition ◽  
Isotope Ratio Mass Spectrometry ◽  
Fish Removal ◽  
Enhanced Diffusion ◽  
Carbon Isotopic ◽  
Low Co2 ◽  
High O2

Abstract. The effects of fish removal on the biogeochemistry and lower-trophic level food web relations were studied in a shallow eutrophied turf lake. Biomanipulation led to an increase in transparency and macrophyte biomass and decrease in phytoplankton abundance, but zooplankton numbers did not increase. Moreover, fish removal resulted in high pH, high O2, low CO2, and more negative δ13CDIC values than expected, which is proposed to be the likely result of chemical enhanced diffusion with large negative fractionation (-13). By combining fluorescence activated cell sorting and isotope ratio mass spectrometry (IRMS) of fatty acids we were able to obtain group specific δ13C signatures and to trace possible shifts in δ13C resulting from fish removal. Fractionation values of green algae (20) and diatoms (22) were uniform and independent of treatment, while fractionation factors of filamentous cyanobacteria were variable between the treatments that differed in CO2 availability. 13C-labeling of the phytoplankton groups showed that biomanipulation led to increased growth rates of green algae and diatoms at the expense of cyanobacteria. Finally, the primary consumer Chydorus appeared to prefer cyanobacteria, whilst Asplanchna grazed predominantly upon eukaryotes.

scholarly journals Aquatic food webs in mangrove and seagrass habitats of Centla Wetland, a Biosphere Reserve in Southeastern Mexico

2010 ◽  
Vol 8 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Manuel Mendoza-Carranza ◽  
David J Hoeinghaus ◽  
Alexandre M Garcia ◽  
Ángel Romero-Rodriguez
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Native Species ◽  
Human Impacts ◽  
Biosphere Reserve ◽  
Isotope Ratios ◽  
Future Research ◽  
Carbon And Nitrogen ◽  
Aquatic Food Webs ◽  
Aquatic Food

Mangrove and seagrass habitats are important components of tropical coastal zones worldwide, and are conspicuous habitats of Centla Wetland Biosphere Reserve (CWBR) in Tabasco, Mexico. In this study, we examine food webs in mangrove- and seagrass-dominated habitats of CWBR using stable isotope ratios of carbon and nitrogen. Our objective was to identify the importance of carbon derived from mangroves and seagrasses to secondary production of aquatic consumers in this poorly studied conservation area. Carbon and nitrogen isotope ratios of basal sources and aquatic consumers indicated that the species-rich food webs of both habitats are dependent on riparian production sources. The abundant Red mangrove Rhizophora mangle appears to be a primary source of carbon for the mangrove creek food web. Even though dense seagrass beds were ubiquitous, most consumers in the lagoon food web appeared to rely on carbon derived from riparian vegetation (e.g. Phragmites australis). The introduced Amazon sailfin catfish Pterygoplichthys pardalis had isotope signatures overlapping with native species (including high-value fisheries species), suggesting potential competition for resources. Future research should examine the role played by terrestrial insects in linking riparian and aquatic food webs, and impacts of the expanding P. pardalis population on ecosystem function and fisheries in CWBR. Our findings can be used as a baseline to reinforce the conservation and management of this important reserve in the face of diverse external and internal human impacts.

scholarly journals Effects of changes in isotopic baselines on the evaluation of food web structure using isotopic functional indices

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9999
Author(s):  
Simon Belle ◽  
Gilbert Cabana
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Horizontal Distribution ◽  
Food Web Structure ◽  
Web Structure ◽  
Functional Richness ◽  
Stable Isotopic ◽  
Aquatic Food ◽  
Set Up ◽  
Functional Indices

Background This study aimed to assess whether ecological inferences from isotopic functional indices (IFIs) are impacted by changes in isotopic baselines in aquatic food webs. We used sudden CO2-outgassing and associated shifts in DIC-δ13C brought by waterfalls as an excellent natural experimental set-up to quantify impacts of changes in algal isotopic baselines on ecological inferences from IFIs. Methods Carbon (δ13C) and nitrogen (δ15N) stable isotopic ratios of invertebrate communities sharing similar structure were measured at above- and below-waterfall sampling sites from five rivers and streams in Southern Quebec (Canada). For each sampled invertebrate community, the six Laymans IFIs were then calculated in the δ -space (δ13C vs. δ15N). Results As expected, isotopic functional richness indices, measuring the overall extent of community trophic space, were strongly sensitive to changes in isotopic baselines unlike other IFIs. Indeed, other IFIs were calculated based on the distribution of species within δ-space and were not strongly impacted by changes in the vertical or horizontal distribution of specimens in the δ-space. Our results highlighted that IFIs exhibited different sensitivities to changes in isotopic baselines, leading to potential misinterpretations of IFIs in river studies where isotopic baselines generally show high temporal and spatial variabilities. The identification of isotopic baselines and their associated variability, and the use of independent trophic tracers to identify the actual energy pathways through food webs must be a prerequisite to IFIs-based studies to strengthen the reliability of ecological inferences of food web structural properties.

Carbon sources for aquatic food webs of riverine and lacustrine tropical waterholes with variable groundwater influence

2017 ◽  
Vol 68 (3) ◽  
pp. 442 ◽  
Author(s):  
N. E. Pettit ◽  
D. M. Warfe ◽  
P. G. Close ◽  
B. J. Pusey ◽  
R. Dobbs ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Isotope Analysis ◽  
Carbon Sources ◽  
Freshwater Wetlands ◽  
Food Sources ◽  
Web Studies ◽  
Aquatic Food Webs ◽  
Aquatic Food ◽  
Groundwater Reserves

Food web studies integrate ecological information and provide understanding of ecosystem function. Aquatic ecosystems of the Kimberley region (north-western Australia) have high conservation significance as hotspots for maintaining local and regional biodiversity. This study investigated the influence of waterhole type and persistence on the strength of consumer reliance on local energy resources for aquatic food webs. Changes in water isotopic composition indicated groundwater inputs were enough to overcome evaporative losses in some waterholes. Other waterholes had varying levels of isotope enrichment suggesting insufficient groundwater input to ‘compensate’ for evaporative loss. C and N isotope analysis indicated considerable overlap among energy sources in waterholes between macrophytes and periphyton but gradient analysis indicated that periphyton is a major carbon source for aquatic consumers. Groundwater-fed waterholes appeared to have higher quality food sources (indicated by lower C:N ratios), but there was minimal evidence that direct groundwater contributions were related to food web processes. Nonetheless, in a region where groundwater is influential in maintaining aquatic habitats, future development of groundwater reserves will likely affect the ecological and cultural value of freshwater wetlands by either reducing their permanence or size or indirectly through possible alteration to the role of periphyton in supporting the food web.

scholarly journals Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon

2020 ◽  
Vol 6 (20) ◽  
pp. eaaz4880 ◽  
Author(s):  
D. M. Walters ◽  
W.F. Cross ◽  
T.A. Kennedy ◽  
C.V. Baxter ◽  
R.O. Hall ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Species Interactions ◽  
Colorado River ◽  
Grand Canyon ◽  
Terrestrial Ecosystems ◽  
Species Traits ◽  
Functional Trait ◽  
Contaminant Exposure ◽  
Aquatic Food

Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator resistant and a trophic dead end for Hg in food webs we studied. Fishes preferred blackflies, which accounted for 56 to 80% of Hg flux to fishes, even where blackflies were rare. Food web properties, i.e., match/mismatch between insect production and fish consumption, governed amounts of Hg retained in the river versus exported to land. An experimental flood redistributed Hg fluxes in the simplified tailwater food web, but not in complex downstream food webs. Recognizing that species traits, species interactions, and disturbance mediate contaminant exposure can improve risk management of linked aquatic-terrestrial ecosystems.

scholarly journals Comparing community response indices in aquatic food web models

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Ágnes Móréh ◽  
Ferenc Jordán
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Aquatic Ecosystems ◽  
Single Species ◽  
Community Response ◽  
Individual Species ◽  
Relative Importance ◽  
Response Functions ◽  
Local Perturbations ◽  
Aquatic Food

Aquatic ecosystems face several major challenges from the introduction and invasion of species, to overfishing. In order to better manage these situations, we need predictive models, where diverse scenarios can be simulated and tested. One key challenge to address is how to quantify the relationships between single-species disturbances and their multispecies effects. Mapping the spread of direct and indirect effects in food webs helps to link species to communities. Since food webs are complex networks of interactions, it is typically not easy to make predictions, so modelling and simulation may help to reveal general patterns. In food web simulations, one can quantify the effects of local perturbations on other species, i.e., community response. This may provide information about the relative importance of individual species and it is also useful to assess the vulnerability of the whole community to local changes. However, community response can be measured in several ways and various response functions give different results. In order to better understand their similarities and differences, we present a comparative study on a reasonable set of community response functions in food web simulations. These results contribute to build more predictive, multi-species models for systems-based conservation and management.

scholarly journals Stable isotopes dissect aquatic food webs from the top to the bottom

2014 ◽  
Vol 11 (8) ◽  
pp. 2357-2371 ◽  
Author(s):  
J. J. Middelburg
Keyword(s):  
Stable Isotopes ◽  
Food Web ◽  
Food Webs ◽  
Web Studies ◽  
Challenges And Opportunities ◽  
Recent Developments ◽  
End To End ◽  
Aquatic Food ◽  
Small Producers ◽  
Web Reconstruction

Abstract. Stable isotopes have been used extensively to study food-web functioning, that is, the flow of energy and matter among organisms. Traditional food-web studies are based on the natural variability of isotopes and are limited to larger organisms that can be physically separated from their environment. Recent developments allow isotope ratio measurements of microbes and this in turn allows the measurement of entire food webs, in other words, from small producers at the bottom to large consumers at the top. Here, I provide a concise review on the use and potential of stable isotopes to reconstruct end-to-end food webs. I will first discuss food web reconstruction based on natural abundances isotope data and will then show that the use of stable isotopes as deliberately added tracers provides complementary information. Finally, challenges and opportunities for end-to-end food web reconstructions in a changing world are discussed.

scholarly journals Food web aggregation: effects on key positions

2021 ◽  
Author(s):  
Emanuele Giacomuzzo ◽  
Ferenc Jordan
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Hierarchical Clustering ◽  
Research Question ◽  
Jaccard Index ◽  
The Other ◽  
Group Model ◽  
Aggregation Methods ◽  
Importance Index ◽  
Aquatic Food

Providing standard definitions of what should be considered as a node in food webs is still an unsolved problem. Especially for comparative and predictive food web modelling, a more systematic understanding is needed for the effects of trophic aggregation procedures. Aggregation is unavoidable during data management. Therefore, it is crucial to know whether food web properties are conserved during this process. Here, we study how different aggregation methods change the positional importance of species in food webs. In particular, we investigated the effects of various aggregation algorithms on 24 indices of importance. Our work was carried out on 76 aquatic food webs coming from the Ecopath with Ecosim database (EcoBase). We considered six main types of aggregation, according to the way that the nodes were clustered. These were (i) hierarchical clustering based on the Jaccard index, (ii) hierarchical clustering based on regular equivalence (REGE), (iii) maximisation of directed modularity, (iv) maximisation of modularity according to modules in which species fed on the same preys, (v) maximisation of modularity according to modules in which species are fed upon by the same predators, and (vi) clustering through the group model. Hierarchical clustering based on the Jaccard index and REGE index outperformed the other four methods on maintaining the relative importance of species for all the indices of importance (except for the contrastatus index, s'). The choice between these two methods should follow our research question and the importance index we are interested in studying. The other four aggregation methods change more the centrality of species, especially the one based on maximising directed modularity. When using these aggregation algorithms, one has to keep in mind that the network will not only be smaller but also provides different information.

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