Top-down control in a detritus-based food web: fish, shredders, and leaf breakdown

Ruetz, Carl R.; Newman, Raymond M.; Vondracek, Bruce

doi:10.1007/s00442-002-0953-1

Cited by 86 publications

(84 citation statements)

References 71 publications

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“…This weak top-down control is likely due to the abundance of morphologically predator-resistant invertebrates in this tributary stream food web (McNeely et al 2007), with approximately 65% of the total benthic invertebrate biomass and 82% of herbivore biomass classified as armored and invulnerable to predation. Though predatory fishes have also been shown to induce trophic cascades on detrital processing rates (Konishi et al 2001, Boyero et al 2007,, but see Ruetz et al 2002), we did not estimate changes in the processing of terrestrial detritus as part of this study. We expect that the processing rates by aquatic invertebrates may be similarly insensitive to top-down control in our study system due to the high abundance of armored taxa within shredder and scraper functional feeding groups.…”

Section: Discussionmentioning

confidence: 77%

Dependence of stream predators on terrestrial prey fluxes: food web responses to subsidized predation

et al. 2013

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Abstract. Resource subsidies in the form of energy, materials, and organisms can support the productivity of recipient ecosystems. When subsidies increase the abundance of top predators, theory predicts that top-down interactions will be strengthened. However, the degree to which subsidies intensify predation should be constrained by the strength of interactions between predators and their prey. To test the potential for subsidies to drive strong top-down control by two stream predators, steelhead (Oncorhynchus mykiss) and Pacific giant salamander (Dicamptodon tenebrosus) we reduced terrestrial prey and manipulated the presence of predators in 32 stream reaches. Prey subsidies supported elevated growth of predatory steelhead in our study system and in the absence of allochthonous prey steelhead experienced a 187% reduction in growth. Despite the high biomass of subsidized predators, there was little support for strong top-down control of herbivore biomass, or a trophic cascade as measured by changes in AFDM and chlorophyll-a. This result was consistent across subsidy treatments, suggesting that predatory steelhead are unable to increase exploitation of aquatic prey in the absence of terrestrial prey subsidies. The potential for top-down control was apparently limited by the fact that most (82%) herbivores in our study system were armored and relatively invulnerable to predation. These results demonstrate the potential importance of behavioral and morphological adaptations that can temper predator prey interactions in highly subsidized ecosystems.

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Section: Discussionmentioning

confidence: 77%

Dependence of stream predators on terrestrial prey fluxes: food web responses to subsidized predation

et al. 2013

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“…Twelve cages (1 Â 1 Â 0.5 m 3 ) with 6-mm mesh on all sides were used to manipulate round goby density. The mesh size was sufficient for the movement of invertebrate prey in and out of cages (e.g., Ruetz et al 2002), while acting as a barrier to round gobies ! 3.8 cm TL.…”

Section: Enclosure Experimentsmentioning

confidence: 99%

“…In situ enclosure and exclosure experiments are a practical way to identify strong interspecific interactions (Power 1992;Ruetz et al 2002;Bartsch et al 2005). First, we used in situ enclosures to examine the direct predatory role of large round gobies on Dreissena densities.…”

Section: Introductionmentioning

confidence: 99%

Round goby predation onDreissenain coastal areas of eastern Lake Michigan

Ruetz

Reneski

Uzarski

2012

Journal of Freshwater Ecology

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Predator-prey interactions between round goby (Neogobius melanostomus) and Dreissena are an important component of the food web in their invaded range in North America and Europe. We conducted two experiments to test the effect of round goby predation on Dreissena in coastal lakes connected to eastern Lake Michigan, USA. First, we conducted a density gradient experiment using 1-m 2 cages stocked with 0 to 15 large round gobies (individuals 4 7.5 cm total length (TL)). Presence of large round gobies significantly reduced Dreissena densities in all cages. Second, we conducted an exclosure experiment (treatments: none, 6-mm, and 24-mm mesh) in four coastal lakes in littoral habitats. Excluding large round gobies did not significantly affect Dreissena densities in any of the lakes, although we did find a significant effect of excluding large-bodied (i.e., animals larger than adult round goby that cannot pass through 24-mm mesh) predators in one lake. In combination, our two experiments showed that the strength of predator-prey interactions between round goby and Dreissena can vary with location and/or conditions. We hypothesize that the strength of predator-prey interactions between round goby and Dreissena vary spatially across the aquatic landscape depending on habitat (e.g., rocky vs. sandy substrates), which is critical for understanding foodweb dynamics, especially in areas where the round goby and Dreissena are invasive.

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“…Resource availability (e.g., Wallace et al 1997, Cross et al 2006 or physical habitat (Huryn andWallace 1987, Chadwick andHuryn 2005) can control secondary production. Yet, the potential for control of secondary production by other groups of animals via predation, competition, or habitat modification is not well understood and has not been tested experimentally despite many studies showing how animal abundance responds to fish predators and competitors (e.g., Forrester 1994, Flecker 1996, Ruetz et al 2002.…”

Section: Introductionmentioning

confidence: 99%

Detritivorous fish indirectly reduce insect secondary production in a tropical river

2011

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Abstract. Dominant animals can indirectly regulate population dynamics and energy flow for many other species in an ecosystem by altering habitat structure and resource availability. However, we know little about the degree to which other taxa can compensate for the loss of these dominant species. By removing animals and measuring responses of other animals as secondary production it is possible to assess how much other taxa can perform similar functions of these dominant taxa. Here we tested the response of aquatic insect secondary production to the loss of a dominant detritivorous fish Prochilodus mariae, in a tropical river, Rio Las Marias, Venezuela. Using an impermeable, plastic curtain, we excluded Prochilodus from one half of a 235-m stream reach for 6 weeks. We measured insect production as biomass times empirically measured body mass-specific growth rates for 8 common taxa constituting 59-74% of insect biomass. Removing Prochilodus increased the standing stock of benthic organic sediment. Biomass of the entire assemblage increased 1.7-fold and insect production for 8 taxa tripled upon exclusion of Prochilodus. Two fast-growing mayfly genera, Tricorythodes and Leptohyphes drove the increased secondary production. Despite low biomass of insects, growth rates were among the highest measured for freshwater insects, and these high growth rates in part caused high secondary production. Although insect production was high in the exclusion reach, insects did not compensate for the loss of Prochilodus in terms of consuming organic sediment showing that the capacity of detritivorous fish to process sediments is higher than that for aquatic insects in this tropical river.

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Top-down control in a detritus-based food web: fish, shredders, and leaf breakdown

Cited by 86 publications

References 71 publications

Dependence of stream predators on terrestrial prey fluxes: food web responses to subsidized predation

Dependence of stream predators on terrestrial prey fluxes: food web responses to subsidized predation

Round goby predation onDreissenain coastal areas of eastern Lake Michigan

Detritivorous fish indirectly reduce insect secondary production in a tropical river

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