scholarly journals Food-web structure and ecosystem services: insights from the Serengeti

2009 ◽  
Vol 364 (1524) ◽  
pp. 1665-1682 ◽  
Author(s):  
Andy Dobson
Keyword(s):  
Ecosystem Services ◽  
Food Web ◽  
Species Interactions ◽  
Large Scale ◽  
Trophic Levels ◽  
Migratory Species ◽  
Food Web Structure ◽  
Natural Habitats ◽  
Serengeti Ecosystem ◽  
Full Diversity

The central organizing theme of this paper is to discuss the dynamics of the Serengeti grassland ecosystem from the perspective of recent developments in food-web theory. The seasonal rainfall patterns that characterize the East African climate create an annually oscillating, large-scale, spatial mosaic of feeding opportunities for the larger ungulates in the Serengeti; this in turn creates a significant annual variation in the food available for their predators. At a smaller spatial scale, periodic fires during the dry season create patches of highly nutritious grazing that are eaten in preference to the surrounding older patches of less palatable vegetation. The species interactions between herbivores and plants, and carnivores and herbivores, are hierarchically nested in the Serengeti food web, with the largest bodied consumers on each trophic level having the broadest diets that include species from a large variety of different habitats in the ecosystem. The different major habitats of the Serengeti are also used in a nested fashion; the highly nutritious forage of the short grass plains is available only to the larger migratory species for a few months each year. The longer grass areas, the woodlands and kopjes (large partially wooded rocky islands in the surrounding mosaic of grassland) contain species that are resident throughout the year; these species often have smaller body size and more specialized diets than the migratory species. Only the larger herbivores and carnivores obtain their nutrition from all the different major habitat types in the ecosystem. The net effect of this is to create a nested hierarchy of subchains of energy flow within the larger Serengeti food web; these flows are seasonally forced by rainfall and operate at different rates in different major branches of the web. The nested structure that couples sequential trophic levels together interacts with annual seasonal variation in the fast and slow chains of nutrient flow in a way that is likely to be central to the stability of the whole web. If the Serengeti is to be successfully conserved as a fully functioning ecosystem, then it is essential that the full diversity of natural habitats be maintained within the greater Serengeti ecosystem. The best way to do this is by controlling the external forces that threaten the boundaries of the ecosystem and by balancing the economic services the park provides between local, national and international needs. I conclude by discussing how the ecosystem services provided by the Serengeti are driven by species on different trophic levels. Tourism provides the largest financial revenue to the national economy, but it could be better organized to provide more sustained revenue to the park. Ultimately, ecotourism needs to be developed in ways that take lessons from the structure of the Serengeti food webs, and in ways that provide tangible benefits to people living around the park while also improving the experience of all visitors.

scholarly journals Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves

2012 ◽  
Vol 70 (1) ◽  
pp. 135-149 ◽  
Author(s):  
Géraldine Lassalle ◽  
Jérémy Lobry ◽  
François Le Loc'h ◽  
Steven Mackinson ◽  
Francisco Sanchez ◽  
...  
Keyword(s):  
Food Web ◽  
Species Interactions ◽  
Trophic Levels ◽  
Channel Structure ◽  
Top Down ◽  
Food Web Structure ◽  
Northeast Atlantic ◽  
Continental Shelves ◽  
Rules Of Thumb ◽  
Energy Pathways

Abstract Lassalle, G., Lobry, J., Le Loc'h, F., Mackinson, S., Sanchez, F., Tomczak, M. T., and Niquil, N. 2013. Ecosystem status and functioning: searching for rules of thumb using an intersite comparison of food-web models of Northeast Atlantic continental shelves. – ICES Journal of Marine Science, 70:135–149. This work aimed to provide a better understanding of how the structure and function of marine ecosystems and trophic control mechanisms influence their response to perturbations. Comparative analysis of Ecopath models of four Northeast Atlantic ecosystems was used to search for rules of thumb defining the similarities and differences between them. Ecosystem indicators, related to the ecology of species interactions, were derived from these models and compared. Two main questions were addressed. (i) What are the main energy pathways and mechanisms of control? (ii) Do these ecosystems exhibit the widespread and potentially stabilizing food-web structure such that top predators couple distinct energy pathways? A strong bentho-pelagic coupling operated over the Bay of Biscay Shelf, while energy reached higher trophic levels mostly through pelagic compartments, in northern areas. Zooplankton was demonstrated to be trophically important in all ecosystems, acting as a regulator of the abundance of small pelagic fish. A latitudinal pattern in flow control was highlighted by this analysis, with a significant contribution of top-down effect at higher latitudes. This top-down control of the Baltic Sea, combined with the fact that this ecosystem did not exhibit the potentially stabilizing two-channel structure, suggested a non-stable environment.

scholarly journals Mesoscale variations in the assemblage structure and trophodynamics of mesozooplankton communities of the Adriatic basin (Mediterranean Sea)

2021 ◽  
Author(s):  
Emanuela Fanelli ◽  
Samuele Menicucci ◽  
Sara Malavolti ◽  
Andrea De Felice ◽  
Iole Leonori
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Mediterranean Sea ◽  
Environmental Variables ◽  
Complex Structure ◽  
Assemblage Structure ◽  
Trophic Levels ◽  
Ecosystem Functions ◽  
Food Web Structure ◽  
Adriatic Basin

Abstract. Zooplankton are critical to the functioning of ocean food webs because of their utter abundance and vital ecosystem roles. Zooplankton communities are highly diverse and thus perform a variety of ecosystem functions, thus changes in their community or food web structure may provide evidence of ecosystem alteration. Assemblage structure and trophodynamics of mesozooplantkon communities were examined across the Adriatic basin, the northernmost and most productive basin of the Mediterranean Sea. Samples were collected in June–July 2019 along coast-offshore transects covering the whole western Adriatic side, consistently environmental variables were also recorded. Results showed a clear separation between samples from the northern-central Adriatic and the southern ones, with a further segregation, although less clear, of inshore vs. off-shore stations, the latter mostly dominated in the central and southern stations by gelatinous plankton. Such patterns were mainly driven by chlorophyll-a concentration (as a proxy of primary production) for northern-central stations, i.e. closer to the Po river input, and by temperature and salinity, for southern ones, with the DistLM model explaining 46 % of total variance. The analysis of stable isotopes of nitrogen and carbon allowed to identify a complex food web characterized by 3 trophic levels from herbivores to carnivores, passing through the mixed feeding behavior of omnivores, shifting from phytoplankton/detritus ingestion to microzooplankton. Trophic structure also spatially varied according to sub-area, with the northern-central sub-areas differing from each other and from the southern stations. Our results highlighted the importance of environmental variables as drivers of zooplanktonic communities and the complex structure of their food webs. Disentangling and considering such complexity is crucial to generate realistic predictions on the functioning of aquatic ecosystems, especially in high productive and, at the same time, overexploited area such as the Adriatic Sea.

Decrease in diatom dominance at lower Si:N ratios alters plankton food webs

2020 ◽  
Vol 42 (4) ◽  
pp. 411-424
Author(s):  
Kriste Makareviciute-Fichtner ◽  
Birte Matthiessen ◽  
Heike K Lotze ◽  
Ulrich Sommer
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Phytoplankton Community ◽  
Plankton Community ◽  
Trophic Levels ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Web Structure ◽  
Copepod Grazing ◽  
Important Food Source

Abstract Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm experiment where we manipulated Si:N ratios and copepod abundance in a Baltic Sea plankton community. In high Si:N treatments, diatoms dominated. Some of them were likely spared from grazing unexpectedly resulting in higher diatom biomass under high copepod grazing. With declining Si:N ratios, dinoflagellates became more abundant under low and picoplankton under high copepod grazing. This altered plankton food web structure: under high Si:N ratios, edible diatoms were directly accessible food for copepods, while under low Si:N ratios, microzooplankton and phago-mixotrophs (mixoplankton) were a more important food source for mesograzers. The response of copepods to changes in the phytoplankton community was complex and copepod density-dependent. We suggest that declining Si:N ratios favor microzoo- and mixoplankton leading to increased complexity of planktonic food webs. Consequences on higher trophic levels will, however, likely be moderated by edibility, nutritional value or toxicity of dominant phytoplankton species.

An Inverse Model Analysis of Planktonic Food Webs in Experimental Lakes

1994 ◽  
Vol 51 (9) ◽  
pp. 2034-2044 ◽  
Author(s):  
Alain F. Vézina ◽  
Michael L. Pace
Keyword(s):  
Food Web ◽  
Heterotrophic Bacteria ◽  
Grazing Pressure ◽  
Inverse Methods ◽  
Trophic Levels ◽  
Microbial Food Web ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Size Groups ◽  
The Impact

We used inverse methods to reconstruct carbon flows in experimental lakes where the fish community had been purposely altered. These analyses were applied to three years of data from a reference lake and two experimental lakes located in Gogebic County, Michigan. We reconstructed seasonally averaged flows among two size groups of phytoplankton, heterotrophic bacteria, microzooplankton, cladocerans, and copepods. The inverse analysis produced significantly different flow networks for the different lakes that agreed qualitatively with known chemical and biological differences between lakes and with other analyses of the impact of fish manipulations on food web structure and dynamics. The results pointed to alterations in grazing pressure on the phytoplankton that parallel changes in the size and abundance of cladocerans and copepods among lakes. Estimated flows through the microbial food web indicated low bacterial production efficiencies and small carbon transfers from the microbial food web to the larger zooplankton. This study demonstrates the use of inverse methods to identify and compare flow patterns across ecosystems and suggests that microbial flows are relatively insensitive to changes at the upper trophic levels.

Lake Michigan offshore ecosystem structure and food web changes from 1987 to 2008

2014 ◽  
Vol 71 (7) ◽  
pp. 1072-1086 ◽  
Author(s):  
Mark W. Rogers ◽  
David B. Bunnell ◽  
Charles P. Madenjian ◽  
David M. Warner
Keyword(s):  
Food Web ◽  
Functional Groups ◽  
Lake Michigan ◽  
Neogobius Melanostomus ◽  
Trophic Levels ◽  
Nutrient Concentrations ◽  
Ecosystem Structure ◽  
Bythotrephes Longimanus ◽  
Nutrient Inputs ◽  
Food Web Structure

Ecosystems undergo dynamic changes owing to species invasions, fisheries management decisions, landscape modifications, and nutrient inputs. At Lake Michigan, new invaders (e.g., dreissenid mussels (Dreissena spp.), spiny water flea (Bythotrephes longimanus), round goby (Neogobius melanostomus)) have proliferated and altered energy transfer pathways, while nutrient concentrations and stocking rates to support fisheries have changed. We developed an ecosystem model to describe food web structure in 1987 and ran simulations through 2008 to evaluate changes in biomass of functional groups, predator consumption, and effects of recently invading species. Keystone functional groups from 1987 were identified as Mysis, burbot (Lota lota), phytoplankton, alewife (Alosa pseudoharengus), nonpredatory cladocerans, and Chinook salmon (Oncorhynchus tshawytscha). Simulations predicted biomass reductions across all trophic levels and predicted biomasses fit observed trends for most functional groups. The effects of invasive species (e.g., dreissenid grazing) increased across simulation years, but were difficult to disentangle from other changes (e.g., declining offshore nutrient concentrations). In total, our model effectively represented recent changes to the Lake Michigan ecosystem and provides an ecosystem-based tool for exploring future resource management scenarios.

scholarly journals Benthic biodiversity and food web structure in the European sector of the Arctic Ocean during spring time

2018 ◽  
Author(s):  
Barbara Oleszczuk ◽  
Katarzyna Grzelak ◽  
Monika Kędra
Keyword(s):  
Sea Ice ◽  
Food Web ◽  
Barents Sea ◽  
Benthic Communities ◽  
Trophic Levels ◽  
The Arctic ◽  
Feeding Guild ◽  
Food Web Structure ◽  
Web Structure ◽  
Ice Conditions

Arctic marine ecosystems are currently facing sea ice decrease. Changes in the sea ice cover will influence the Organic Matter (OM) fluxes to the bottom and thus benthic communities. We aimed to examine meio- and macrobenthic biodiversity and community structure, and food web, with use of stable isotopes of carbon (δ13C) and nitrogen (δ15N), in relation to depth, sea ice type, and bloom stage. Benthic samples were collected in Svalbard area during spring time in 2015 and 2016 along with samples of particulate and sediment OM. Svalbard fjords, Storfjorden, Barents Sea shelf, continental slope, and Nansen Basin were characterized by different environmental settings including various sea ice conditions, bloom stage, sediment OM and particulate OM in bottom water. The highest biodiversity and biomass were found at the shelf and slope stations where intensive bloom was observed and was related to higher concentrations of fresh, high-quality OM. Low benthic infaunal diversity, abundance, and biomass were noted in fjords and deep stations where quality and quantity of OM was markedly lower. Deposit feeders were the only feeding guild sampled in the deep stations while at other stations 3-4 trophic levels were found.

scholarly journals Predation and competition among larval salamanders : the influence of density dependence, phenology, food web structure and habitat complexity

2016 ◽  
Author(s):  
◽  
Thomas Lee Anderson
Keyword(s):  
Body Size ◽  
Food Web ◽  
Density Dependence ◽  
Food Webs ◽  
Species Interactions ◽  
Habitat Complexity ◽  
Food Web Structure ◽  
Phenological Shifts ◽  
Ringed Salamander

The influence of biotic and abiotic factors on species interactions and overall community structure has long interested ecologists. Despite a legacy of interest, there is still ambiguity into the role of biotic and abiotic factors due to highly nuanced, complex networks of interactions that are difficult to comprehend. Yet, understanding how such nuances is an essential goal to determine how they affect population and community structure. Thus, the goal of my dissertation was to understand how multiple biotic and abiotic mechanisms alter interactions among larval stages of two pond-breeding salamanders. Larval stages of pond-breeding salamanders represent an excellent system for understanding how species interactions vary along abiotic and biotic gradients. Intra-and interspecific interactions are frequently determined by size differences among individuals, where larger larvae are predators of smaller larvae and can out-compete them for shared resources. However, when size differences are minimized, only competition occurs. Such conjoined competition and predation is termed intraguild predation, and is a common interaction in many taxa. The factors that determine size differences among individuals (both within and between species) are critical towards to determining both the type of interaction, as well as the strength of such interactions. The focal species I used were the ringed salamander (Ambystoma annulatum) and spotted salamander (A. maculatum). The former breeds earlier than the latter, creating a larval size advantage which results in predation as the dominant interaction between species. However, factors that influence growth rates of ringed salamanders could result in minimized size differences, resulting in a change to the strength or type of interaction that occurs. For my dissertation, I experimentally investigated three different processes that were expected to affect the relative importance of predation and competition: density dependence, food web structure, and phenological shifts. In my first chapter, I tested whether the density of ringed salamanders influenced their growth rates to such a degree that the interaction type with spotted salamanders would switch from predation to competition. I found that increased intraspecific competition in ringed salamanders reduced their body size and increased their larval period length. However, intraspecific competition did not reduce their size to such a degree that predation on spotted salamanders was precluded. Spotted salamanders showed decreased survival and increased size at higher predator densities, indicative of thinning effects. The period of overlap in ponds also increased at higher predator densities, resulting in a larger temporal window for interactions to occur. In my second chapter, I tested how six different top predator food webs would influence intraguild predation between ringed and spotted salamanders. I also tested whether food web configuration would be simultaneously impacted by increased habitat complexity. I found that ringed salamander body size and survival were unaffected by habitat complexity, and that only certain combinations of predators affected these demographic rates. Spotted salamander body size and survival showed positive and negative relationships with ringed salamander survival, but the strength of these relationships varied depending on the predator and habitat complexity treatment. Thus, pairwise interactions may not exemplify typical interactions when embedded in more complex food webs with other predators. For my third chapter, I investigated whether phenological shifts in both the ringed and spotted salamanders, simultaneous to density dependence in the ringed salamander would influence the type and strength of their interactions. I found ringed salamander survival varied with phenological shifts but only when at high intraspecific densities. Spotted salamanders were relatively unaffected by phenological shifts, and that their interactions were, similar to the previous chapters, influenced primarily by survival of ringed salamanders. As phenological shifts are predicted for many species with climate change, this study highlights that not all species interactions will be subsequently affected, and that other underlying factors (e.g. density dependence) may be more important. Thus, the most important findings of my dissertation include 1) predator density can be a dominant factor in species interactions, 2) pairwise interactions may change when embedded in different habitats or food webs in non-intuitive ways, and 3) simultaneously testing multiple mechanisms can elicit a greater understanding of the relative importance of different ecological processes.

scholarly journals Food web structure of the epibenthic community at the sea ice edge in Baffin Bay, Canada

2018 ◽  
Author(s):  
Gustavo Yunda-Guarin ◽  
Philippe Archambault ◽  
Guillaume Massé ◽  
Christian Nozais
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Food Web ◽  
Trophic Levels ◽  
The Arctic ◽  
Feeding Guilds ◽  
Food Web Structure ◽  
Baffin Bay ◽  
Ice Edge ◽  
Sea Ice Edge

In polar areas, the pelagic-benthic coupling plays a fundamental role in ensuring organic matter flow across depths and trophic levels. Climate change impacts the Arctic’s physical environment and ecosystem functioning, affecting the sequestration of carbon, the structure and efficiency of the benthic food web and its resilience.In the Arctic Ocean, highest atmospheric warming tendencies (by ~0.5°C) occur in the east of Baffin Bay making this area an ideal site to study the effects of climate change on benthic communities. We sampled epibenthic organisms at 13 stations bordering the sea ice between June and July 2016. The epibenthic taxonomic composition was identified and grouped by feeding guilds. Isotopic signatures (δ13C - δ15N), trophic levels and trophic separation and redundancy were measured and quantified at each station. In the light of the results obtained, the stability of the benthic community in the Baffin Bay at the sea ice edge is discussed.

scholarly journals Constraints and variation in food web link-species space

2021 ◽  
Vol 17 (4) ◽  
Author(s):  
Jean P. Gibert ◽  
Daniel J. Wieczynski
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Empirical Data ◽  
Species Interactions ◽  
Fundamental Aspect ◽  
Food Web Structure ◽  
Web Structure ◽  
Scaling Relationship ◽  
The Relationship ◽  
Standing Question

Predicting food web structure in future climates is a pressing goal of ecology. These predictions may be impossible without a solid understanding of the factors that structure current food webs. The most fundamental aspect of food web structure—the relationship between the number of links and species—is still poorly understood. Some species interactions may be physically or physiologically ‘forbidden'—like consumption by non-consumer species—with possible consequences for food web structure. We show that accounting for these ‘forbidden interactions' constrains the feasible link-species space, in tight agreement with empirical data. Rather than following one particular scaling relationship, food webs are distributed throughout this space according to shared biotic and abiotic features. Our study provides new insights into the long-standing question of which factors determine this fundamental aspect of food web structure.

scholarly journals The rise of the three-spined stickleback – eco-evolutionary consequences of a mesopredator release

2020 ◽  
Author(s):  
Britas Klemens Eriksson ◽  
Casey Yanos ◽  
Sarah Bourlat ◽  
Serena Donadi ◽  
Michael C. Fontaine ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Stomach Content ◽  
Ecological Effects ◽  
Trophic Levels ◽  
Predatory Fish ◽  
Series Data ◽  
Food Web Structure ◽  
Benthic Production ◽  
Invertebrate Herbivores

AbstractDeclines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human-induced rapid evolution may in turn affect ecological dynamics. In the central Baltic Sea, abundances of the mesopredatory fish, the three-spined stickleback (Gasterosteus aculeatus), have increased dramatically during the past decades. Time-series data covering 22 years show that this increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We studied the interaction between evolutionary and ecological effects of this mesopredator take-over, by surveying the armour plate morphology of stickleback and the structure of the associated food web. First, we investigated the distribution of different stickleback phenotypes depending on predator abundances and benthic production; and described the stomach content of the stickleback phenotypes using metabarcoding. Second, we explored differences in the relation between different trophic levels and benthic production, between bays where the relative abundance of fish was dominated by stickleback or not; and compared this to previous cage-experiments to support causality of detected correlations. We found two distinct lateral armour plate phenotypes of stickleback, incompletely and completely plated. The proportion of incompletely plated individuals increased with increasing benthic production and decreasing abundances of adult perch. Stomach content analyses showed that the completely plated individuals had a stronger preference for invertebrate herbivores (amphipods) than the incompletely plated ones. In addition, predator dominance interacted with ecosystem production to determine food web structure and the propagation of a trophic cascade: with increasing production, biomass accumulated on the first (macroalgae) and third (stickleback) trophic levels in stickleback-dominated bays, but on the second trophic level (invertebrate herbivores) in perch-dominated bays. Since armour plates are defence structures favoured by natural selection in the presence of fish predators, the phenotype distribution suggest that a novel low-predation regime favours sticklebacks with less armour. Our results indicate that an interaction between evolutionary and ecological effects of the stickleback take-over has the potential to affect food web dynamics.

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