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 Large herbivorous wildlife and livestock differentially influence the relative importance of different sources of carbon for riverine food webs

2021 ◽  
Author(s):  
Frank O. Masese ◽  
Thomas Fuss ◽  
Lukas Bistarelli ◽  
Caroline Buchen-Tschiskale ◽  
Gabriel Singer
Keyword(s):  
Organic Matter ◽  
Food Webs ◽  
Aquatic Ecosystems ◽  
Carbon Sources ◽  
Large River ◽  
Livestock Grazing ◽  
Relative Importance ◽  
River Continuum ◽  
Aquatic Food ◽  
Different Sources

In many regions around the world, large populations of native wildlife have declined or been replaced by livestock grazing areas and farmlands, with consequences on terrestrial-aquatic ecosystems connectivity and trophic resources supporting food webs in aquatic ecosystems. The river continuum concept (RCC) and the riverine productivity model (RPM) predict a shift of carbon supplying aquatic food webs along the river: from terrestrial inputs in low-order streams to autochthonous production in mid-sized rivers. Here, we studied the influence of replacing large wildlife (mainly hippos) with livestock on the relative importance of C3 vegetation, C4 grasses and periphyton on macroinvertebrates in the Mara River, which is an African montane-savanna river known to receive large subsidy fluxes of terrestrial carbon and nutrients mediated by LMH, both wildlife and livestock. Using stable carbon (δ13C) and nitrogen (δ15N) isotopes, we identified spatial patterns of the relative importance of allochthonous carbon from C3 and C4 plants (woody vegetation and grasses, respectively) and autochthonous carbon from periphyton for macroinvertebrates at various sites of the Mara River and its tributaries. Potential organic carbon sources and invertebrates were sampled at 80 sites spanning stream orders 1 to 7, various catchment land uses (forest, agriculture and grasslands) and different loading rates of organic matter and nutrients by LMH (livestock and wildlife, i.e., hippopotamus). The importance of different sources of carbon along the river did not follow predictions of RCC and RPM. First, the importance of C3 and C4 carbon was not related to river order or location along the fluvial continuum but to the loading of organic matter (dung) by both wildlife and livestock. Notably, C4 carbon was important for macroinvertebrates even in large river sections inhabited by hippos. Second, even in small 1st -3rd order forested streams, autochthonous carbon was a major source of energy for macroinvertebrates, and this was fostered by livestock inputs fuelling aquatic primary production throughout the river network. Importantly, our results show that replacing wildlife (hippos) with livestock shifts river systems towards greater reliance on autochthonous carbon through an algae-grazer pathway as opposed to reliance on allochthonous inputs of C4 carbon through a detrital pathway.

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 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.

scholarly journals Understanding the structure and functioning of polar pelagic ecosystems to predict the impacts of change

2016 ◽  
Vol 283 (1844) ◽  
pp. 20161646 ◽  
Author(s):  
E. J. Murphy ◽  
R. D. Cavanagh ◽  
K. F. Drinkwater ◽  
S. M. Grant ◽  
J. J. Heymans ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Energy Flow ◽  
Life Histories ◽  
Trophic Levels ◽  
Individual Species ◽  
Polar Regions ◽  
Ecosystem Structure ◽  
Food Web Structure ◽  
Pelagic Ecosystems

The determinants of the structure, functioning and resilience of pelagic ecosystems across most of the polar regions are not well known. Improved understanding is essential for assessing the value of biodiversity and predicting the effects of change (including in biodiversity) on these ecosystems and the services they maintain. Here we focus on the trophic interactions that underpin ecosystem structure, developing comparative analyses of how polar pelagic food webs vary in relation to the environment. We highlight that there is not a singular, generic Arctic or Antarctic pelagic food web, and, although there are characteristic pathways of energy flow dominated by a small number of species, alternative routes are important for maintaining energy transfer and resilience. These more complex routes cannot, however, provide the same rate of energy flow to highest trophic-level species. Food-web structure may be similar in different regions, but the individual species that dominate mid-trophic levels vary across polar regions. The characteristics (traits) of these species are also different and these differences influence a range of food-web processes. Low functional redundancy at key trophic levels makes these ecosystems particularly sensitive to change. To develop models for projecting responses of polar ecosystems to future environmental change, we propose a conceptual framework that links the life histories of pelagic species and the structure of polar food webs.

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 Copper Pollution Increases the Relative Importance of Predation Risk in an Aquatic Food Web

PLoS ONE ◽  
2015 ◽  
Vol 10 (7) ◽  
pp. e0133329 ◽  
Author(s):  
Christopher Kent Kwan ◽  
Eric Sanford ◽  
Jeremy Long
Keyword(s):  
Food Web ◽  
Predation Risk ◽  
Relative Importance ◽  
Aquatic Food Web ◽  
Aquatic Food ◽  
Copper Pollution

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.

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