Differential responses of size-based functional groups to bottom-up and top-down perturbations in pelagic food webs: a meta-analysis

The debates about the extent to which phytoplankton in freshwater ecosystems are regulated by top-down or bottom-up forces have been ongoing for decades. This study examines the effects of bottom-up and top-down factors on the phytoplankton functional groups in a eutrophic lake. Phytoplankton and zooplankton were sampled and physical-chemical variables measured from May 2019 to October 2019 in Lake Hulun, China. Approximately 43 phytoplankton species were observed and grouped into 23 functional groups. For the zooplankton, about 27 species were observed and classified into 8 functional groups. The study revealed that the bottom-up effects of physical-chemical variables on some phytoplankton functional groups was stronger than the top-down effects of zooplankton. Water temperature (WT), total phosphorus (TP), total nitrogen (TN), conductivity (Cond), water transparency (SD), and dissolved oxygen (DO) significant influence the biomass of the phytoplankton functional groups. The biomass of phytoplankton functional groups was influenced positively by nutrient availability likely because nutrients influence the growth and reproduction of phytoplankton in freshwater. WT and DO had a positive influence on biomass of phytoplankton functional groups. Conversely, phytoplankton biomass revealed a decreasing trend when SD and Cond significantly increased. This study showed that zooplankton functional groups were positively correlated with phytoplankton biomass implying that the top-down control of phytoplankton by the zooplankton in the lake is not strong enough to produce a negative effect. It is evident that the zooplankton functional groups in Lake Hulun are controlled more by bottom-up force than top-down.

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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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Racial prototypicality cues exacerbate racial bias in pain perception from the bottom up and the top down

10.31234/osf.io/6gu8j ◽

2020 ◽

Author(s):

Alexis Drain ◽

Azaadeh Goharzad ◽

Jennie Qu-Lee ◽

Jingrun Lin ◽

Peter Mende-Siedlecki

Keyword(s):

Pain Perception ◽

Racial Bias ◽

Meta Analysis ◽

Structural Features ◽

Facial Structure ◽

Top Down ◽

Bottom Up ◽

Race And Gender ◽

Pain Outcomes ◽

And Gender

Racial disparities in pain care may stem, in part, from a perceptual source. While perceptual disruptions in recognizing painful expressions on Black faces have been demonstrated under tightly-controlled conditions (e.g., controlling for low-level stimulus differences in luminance and facial structure, using all male stimuli), these effects may be exacerbated by cues to racial prototypicality. Indeed, both bottom-up (e.g., skin tone, facial structure) and top-down (e.g., stereotype associations between race and gender) factors related to racial prototypicality moderate social perception, with some evidence pointing towards deleterious consequences in the domain of health. Here, we assessed whether these factors shape racial bias in pain perception: we examined the effect of racially prototypical features in Experiments 1 and 2 and target gender in a meta-analysis across five additional experiments. Overall, darker skin tones were associated with more stringent pain perception and more conservative treatment, while racially prototypic structural features exacerbated racial bias in pain outcomes. Moreover, target gender reliably moderated the effect of race on pain outcomes: racial biases in both pain perception and treatment were larger for male (versus female) targets. Taken together, these data demonstrate the overall robustness of racial bias in pain perception and its facilitation of gaps in treatment, but also the extent to which these biases are moderated by both bottom-up and top-down factors related to racial prototypicality.

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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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