scholarly journals Plant-mediated community structure of spring-fed, coastal rivers

2019 ◽  
Author(s):  
Matthew V. Lauretta ◽  
William E. Pine ◽  
Carl J. Walters ◽  
Thomas K. Frazer
Keyword(s):  
Community Structure ◽  
Primary Production ◽  
Food Web ◽  
Vascular Plant ◽  
Search Efficiency ◽  
Top Down ◽  
Food Web Structure ◽  
Bottom Up ◽  
Model Predictions ◽  
Filamentous Macroalgae

AbstractQuantifying ecosystem-level processes that drive community structure and function is key to the development of effective environmental restoration and management programs. To assess the effects of large-scale aquatic vegetation loss on fish and invertebrate communities in Florida estuaries, we quantified and compared the food webs of two adjacent spring-fed rivers that flow into the Gulf of Mexico. We constructed a food web model using field-based estimates of community absolute biomass and trophic interactions of a highly productive vegetated river, and modeled long-term simulations of vascular plant decline coupled with seasonal production of filamentous macroalgae. We then compared ecosystem model predictions to observed community structure of the second river that has undergone extensive vegetative habitat loss, including extirpation of several vascular plant species. Alternative models incorporating bottom-up regulation (decreased primary production resulting from plant loss) versus coupled top-down effects (compensatory predator search efficiency) were ranked by goodness-of-fit tests of model predictions to the empirical community observations. Our best model for predicting community responses to vascular plant loss incorporated coupled effects of decreased primary production (bottom-up), increased prey search efficiency of large-bodied fishes at low vascular plant density (top-down), and decreased prey search efficiency of small-bodied fishes with increased biomass of filamentous macroalgae (bottom-up). The results of this study indicate that the loss of vascular plants from the coastal river ecosystem may alter the food web structure and result in a net decline in the biomass of fishes. These results are highly relevant to ongoing landscape-level restoration programs intended to improve aesthetics and ecosystem function of coastal spring-fed rivers by highlighting how the structure of these communities can be regulated both by resource availability and consumption. Restoration programs will need to acknowledge and incorporate both to be successful.

Bottom-up carbon subsidies and top-down predation pressure interact to affect aquatic food web structure

Oikos ◽  
2010 ◽  
Vol 120 (2) ◽  
pp. 311-320 ◽  
Author(s):  
C. L. Faithfull ◽  
M. Huss ◽  
T. Vrede ◽  
A.-K. Bergström
Keyword(s):  
Food Web ◽  
Predation Pressure ◽  
Aquatic Food Web ◽  
Top Down ◽  
Food Web Structure ◽  
Bottom Up ◽  
Web Structure ◽  
Aquatic Food

Trophic Relationships in Freshwater Pelagic Ecosystems

1986 ◽  
Vol 43 (8) ◽  
pp. 1571-1581 ◽  
Author(s):  
Donald J. McQueen ◽  
John R. Post ◽  
Edward L. Mills
Keyword(s):  
Food Web ◽  
Trophic Status ◽  
Size Structure ◽  
Trophic Relationships ◽  
Top Down ◽  
Eutrophic Lakes ◽  
Bottom Up ◽  
Coefficients Of Variation ◽  
Step Down ◽  
Pelagic Ecosystems

Relative impacts of bottom-up (producer controlled) and top-down (consumer controlled) forces on the biomass and size structure of five major components of freshwater pelagic systems (piscivores, planktivores, zooplankton, phytoplankton, and total phosphorus availability) were estimated. Predictions that emerge are (1) maximum biomass at each trophic level is controlled from below (bottom-up) by nutrient availability, (2) this bottom-up regulation is strongest at the bottom of the food web (i.e. phosphorus → phytoplankton) and weakens by a factor of 2 with each succeeding step up the food web, (3) as energy moves up a food web, the predictability of bottom-up interactions decreases, (4) near the top of the food web, top-down (predator mediated) interactions are strong and have low coefficients of variation, but weaken with every step down the food web, (5) variability around the bottom-up regressions can always be explained by top-down forces, and (6) interplay between top-down and bottom-up effects changes with the trophic status of lakes. In eutrophic lakes, top-down effects are strong for piscivore → zooplankton, weaker for planktivore → zooplankton, and have little impact for zooplankton → phytoplankton. For oligotrophic lakes, the model predicts that top-down effects are not strongly buffered, so that zooplankton → phytoplankton interactions are significant.

scholarly journals Warming and nitrogen affect size structuring and density dependence in a host–parasitoid food web

2012 ◽  
Vol 367 (1605) ◽  
pp. 3033-3041 ◽  
Author(s):  
Claudio de Sassi ◽  
Phillip P. A. Staniczenko ◽  
Jason M. Tylianakis
Keyword(s):  
Body Size ◽  
Food Web ◽  
Food Webs ◽  
Global Changes ◽  
Ecological Communities ◽  
Food Web Structure ◽  
Bottom Up ◽  
Mediated Effects ◽  
Web Structure ◽  
Nitrogen Treatments

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.

Is pelagic top-down control in lakes augmented by benthic energy pathways?

2005 ◽  
Vol 62 (6) ◽  
pp. 1422-1431 ◽  
Author(s):  
M Jake Vander Zanden ◽  
Timothy E Essington ◽  
Yvonne Vadeboncoeur
Keyword(s):  
Food Web ◽  
Energy Flow ◽  
Standing Stock ◽  
Fold Increase ◽  
Trophic Dynamics ◽  
Prey Fish ◽  
Top Down ◽  
Food Web Structure ◽  
Contrast Analysis ◽  
Dynamic Perspective

Modern food web studies are typically conducted from a trophic dynamic perspective that focuses on combined roles of top-down and bottom-up forces in regulating food web structure. Recognition of spatial food web subsidies in diverse ecosystems highlights the importance of energy flow as a foundation for understanding trophic dynamics. Here, we consider how different energy flow configurations might affect trophic dynamics in north-temperate lakes. A literature review revealed that littoral piscivores exert top-down control on prey fishes. In contrast, analysis of littoral predator diets indicated extensive omnivory and heavy reliance on zoobenthic prey. We explored this uncoupling between trophic dynamics (piscivores regulate prey fish) and energy flow (zoobenthos in piscivore diets) using a biomass dynamic model. This model compared top-down impacts of a piscivore on prey fishes under two scenarios: consumption of prey fish only and consumption of prey fish plus zoobenthos. The model predicted that elimination of zoobenthivory leads to a 50% reduction in piscivore standing stock and concomitant 2.5-fold increase in prey fish abundance (i.e., zoobenthivory plays a key role in mediating pelagic top-down control). These results highlight the role of benthic–pelagic linkages in regulating trophic dynamics and underscore the value of whole-ecosystem approaches to the study of food webs.

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

2013 ◽  
Vol 71 (2) ◽  
pp. 406-416 ◽  
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.

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

2012 ◽  
Vol 367 (1605) ◽  
pp. 3008-3017 ◽  
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.

The effects of top–down versus bottom–up control on benthic coral reef community structure

Oecologia ◽  
2010 ◽  
Vol 163 (2) ◽  
pp. 497-507 ◽  
Author(s):  
Jennifer E. Smith ◽  
Cynthia L. Hunter ◽  
Celia M. Smith
Keyword(s):  
Community Structure ◽  
Coral Reef ◽  
Top Down ◽  
Bottom Up ◽  
Coral Reef Community ◽  
Reef Community

Top-down vs. bottom-up regulation of herbaceous primary production and composition in an arid, urbanizing ecosystem

2015 ◽  
Vol 116 ◽  
pp. 103-114 ◽  
Author(s):  
Michelle K. Davis ◽  
Elizabeth M. Cook ◽  
Scott L. Collins ◽  
Sharon J. Hall
Keyword(s):  
Primary Production ◽  
Top Down ◽  
Bottom Up

scholarly journals A review of bottom-up vs. top-down control of sponges on Caribbean fore-reefs: what’s old, what’s new, and future directions

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4343 ◽  
Author(s):  
Joseph R. Pawlik ◽  
Tse-Lynn Loh ◽  
Steven E. McMurray
Keyword(s):  
Community Structure ◽  
Past Research ◽  
Fish Predation ◽  
Sponge Species ◽  
Top Down ◽  
Bottom Up ◽  
Fore Reef ◽  
The Past ◽  
The Impact ◽  
Hawksbill Turtles

Interest in the ecology of sponges on coral reefs has grown in recent years with mounting evidence that sponges are becoming dominant members of reef communities, particularly in the Caribbean. New estimates of water column processing by sponge pumping activities combined with discoveries related to carbon and nutrient cycling have led to novel hypotheses about the role of sponges in reef ecosystem function. Among these developments, a debate has emerged about the relative effects of bottom-up (food availability) and top-down (predation) control on the community of sponges on Caribbean fore-reefs. In this review, we evaluate the impact of the latest findings on the debate, as well as provide new insights based on older citations. Recent studies that employed different research methods have demonstrated that dissolved organic carbon (DOC) and detritus are the principal sources of food for a growing list of sponge species, challenging the idea that the relative availability of living picoplankton is the sole proxy for sponge growth or abundance. New reports have confirmed earlier findings that reef macroalgae release labile DOC available for sponge nutrition. Evidence for top-down control of sponge community structure by fish predation is further supported by gut content studies and historical population estimates of hawksbill turtles, which likely had a much greater impact on relative sponge abundances on Caribbean reefs of the past. Implicit to investigations designed to address the bottom-up vs. top-down debate are appropriate studies of Caribbean fore-reef environments, where benthic communities are relatively homogeneous and terrestrial influences and abiotic effects are minimized. One recent study designed to test both aspects of the debate did so using experiments conducted entirely in shallow lagoonal habitats dominated by mangroves and seagrass beds. The top-down results from this study are reinterpreted as supporting past research demonstrating predator preferences for sponge species that are abundant in these lagoonal habitats, but grazed away in fore-reef habitats. We conclude that sponge communities on Caribbean fore-reefs of the past and present are largely structured by predation, and offer new directions for research, such as determining the environmental conditions under which sponges may be food-limited (e.g., deep sea, lagoonal habitats) and monitoring changes in sponge community structure as populations of hawksbill turtles rebound.

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