Bottom-up regulation of food webs in shallow Baltic estuaries

Body size is a major factor constraining the trophic structure and functioning of ecological communities. Food webs are known to respond to changes in basal resource abundance, and climate change can initiate compounding bottom-up effects on food-web structure through altered resource availability and quality. However, the effects of climate and co-occurring global changes, such as nitrogen deposition, on the density and size relationships between resources and consumers are unknown, particularly in host–parasitoid food webs, where size structuring is less apparent. We use a Bayesian modelling approach to explore the role of consumer and resource density and body size on host–parasitoid food webs assembled from a field experiment with factorial warming and nitrogen treatments. We show that the treatments increased resource (host) availability and quality (size), leading to measureable changes in parasitoid feeding behaviour. Parasitoids interacted less evenly within their host range and increasingly focused on abundant and high-quality (i.e. larger) hosts. In summary, we present evidence that climate-mediated bottom-up effects can significantly alter food-web structure through both density- and trait-mediated effects.

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Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

ICES Journal of Marine Science ◽

10.1093/icesjms/fst137 ◽

2013 ◽

Vol 71 (2) ◽

pp. 406-416 ◽

Cited By ~ 6

Author(s):

T. O. M. Reilly ◽

H. M. Fraser ◽

R. J. Fryer ◽

J. Clarke ◽

S. P. R. Greenstreet

Keyword(s):

Food Web ◽

Food Webs ◽

Trophic Levels ◽

Top Down ◽

Bottom Up ◽

Control Processes ◽

Top Predators ◽

Environmental Status ◽

Fish Predators ◽

Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

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Warming shifts top-down and bottom-up control of pond food web structure and function

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2012.0243 ◽

2012 ◽

Vol 367 (1605) ◽

pp. 3008-3017 ◽

Cited By ~ 158

Author(s):

Jonathan B. Shurin ◽

Jessica L. Clasen ◽

Hamish S. Greig ◽

Pavel Kratina ◽

Patrick L. Thompson

Keyword(s):

Food Webs ◽

Environmental Changes ◽

Lytic Cycle ◽

Top Down ◽

Food Web Structure ◽

Bottom Up ◽

Positive Effects ◽

Freshwater Pond ◽

Aquatic Food ◽

The Impact

The effects of global and local environmental changes are transmitted through networks of interacting organisms to shape the structure of communities and the dynamics of ecosystems. We tested the impact of elevated temperature on the top-down and bottom-up forces structuring experimental freshwater pond food webs in western Canada over 16 months. Experimental warming was crossed with treatments manipulating the presence of planktivorous fish and eutrophication through enhanced nutrient supply. We found that higher temperatures produced top-heavy food webs with lower biomass of benthic and pelagic producers, equivalent biomass of zooplankton, zoobenthos and pelagic bacteria, and more pelagic viruses. Eutrophication increased the biomass of all organisms studied, while fish had cascading positive effects on periphyton, phytoplankton and bacteria, and reduced biomass of invertebrates. Surprisingly, virus biomass was reduced in the presence of fish, suggesting the possibility for complex mechanisms of top-down control of the lytic cycle. Warming reduced the effects of eutrophication on periphyton, and magnified the already strong effects of fish on phytoplankton and bacteria. Warming, fish and nutrients all increased whole-system rates of net production despite their distinct impacts on the distribution of biomass between producers and consumers, plankton and benthos, and microbes and macrobes. Our results indicate that warming exerts a host of indirect effects on aquatic food webs mediated through shifts in the magnitudes of top-down and bottom-up forcing.

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Restoring aquatic food webs bottom-up : Improving trophic transfer through lake restoration project Marker Wadden

10.18174/555439 ◽

2021 ◽

Author(s):

Hui Jin

Keyword(s):

Food Webs ◽

Lake Restoration ◽

Trophic Transfer ◽

Bottom Up ◽

Restoration Project ◽

Aquatic Food Webs ◽

Aquatic Food

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Faculty of 1000 evaluation for Simple rules describe bottom-up and top-down control in food webs with alternative energy pathways.

F1000 - Post-publication peer review of the biomedical literature ◽

10.3410/f.717951135.793456437 ◽

2012 ◽

Author(s):

Don DeAngelis ◽

Jiang Jiang

Keyword(s):

Food Webs ◽

Alternative Energy ◽

Top Down ◽

Bottom Up ◽

Simple Rules ◽

Energy Pathways

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The meaning of functional trait composition of food webs for ecosystem functioning

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0268 ◽

2016 ◽

Vol 371 (1694) ◽

pp. 20150268 ◽

Cited By ~ 60

Author(s):

Dominique Gravel ◽

Camille Albouy ◽

Wilfried Thuiller

Keyword(s):

Food Web ◽

Food Webs ◽

Functional Diversity ◽

Ecosystem Functioning ◽

Functional Trait ◽

Plant Ecology ◽

Functional Composition ◽

Top Down ◽

Bottom Up ◽

Functional Trait Diversity

There is a growing interest in using trait-based approaches to characterize the functional structure of animal communities. Quantitative methods have been derived mostly for plant ecology, but it is now common to characterize the functional composition of various systems such as soils, coral reefs, pelagic food webs or terrestrial vertebrate communities. With the ever-increasing availability of distribution and trait data, a quantitative method to represent the different roles of animals in a community promise to find generalities that will facilitate cross-system comparisons. There is, however, currently no theory relating the functional composition of food webs to their dynamics and properties. The intuitive interpretation that more functional diversity leads to higher resource exploitation and better ecosystem functioning was brought from plant ecology and does not apply readily to food webs. Here we appraise whether there are interpretable metrics to describe the functional composition of food webs that could foster a better understanding of their structure and functioning. We first distinguish the various roles that traits have on food web topology, resource extraction (bottom-up effects), trophic regulation (top-down effects), and the ability to keep energy and materials within the community. We then discuss positive effects of functional trait diversity on food webs, such as niche construction and bottom-up effects. We follow with a discussion on the negative effects of functional diversity, such as enhanced competition (both exploitation and apparent) and top-down control. Our review reveals that most of our current understanding of the impact of functional trait diversity on food web properties and functioning comes from an over-simplistic representation of network structure with well-defined levels. We, therefore, conclude with propositions for new research avenues for both theoreticians and empiricists.

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