Quantifying the top-down and bottom-up effects of a non-native grazer in freshwaters

Capps, Krista A.; Ulseth, Amber J.; Flecker, Alexander S.

doi:10.1007/s10530-014-0793-z

Cited by 22 publications

(14 citation statements)

References 57 publications

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“…Removal or addition of vertebrates has had obvious impacts on standing stocks of organic matter in other tropical streams, e.g., grazing tadpoles , grazing armored catfish (Capps et al 2015), or detritivorous fish Taylor 2004, Taylor et al 2006), but we noted no effects of guppy presence on biofilm biomass or chlorophyll a standing stock despite increased primary production in guppy reaches. Since guppies are omnivorous (Zandona et al 2011), they are also unlikely to exert top-down effects of the same magnitude as a predator.…”

Section: Discussioncontrasting

confidence: 49%

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Fish introductions and light modulate food web fluxes in tropical streams: a whole‐ecosystem experimental approach

Collins

Thomas

Heatherly

et al. 2016

Ecology

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Decades of ecological study have demonstrated the importance of top‐down and bottom‐up controls on food webs, yet few studies within this context have quantified the magnitude of energy and material fluxes at the whole‐ecosystem scale. We examined top‐down and bottom‐up effects on food web fluxes using a field experiment that manipulated the presence of a consumer, the Trinidadian guppy Poecilia reticulata, and the production of basal resources by thinning the riparian forest canopy to increase incident light. To gauge the effects of these reach‐scale manipulations on food web fluxes, we used a nitrogen (15N) stable isotope tracer to compare basal resource treatments (thinned canopy vs. control) and consumer treatments (guppy introduction vs. control). The thinned canopy stream had higher primary production than the natural canopy control, leading to increased N fluxes to invertebrates that feed on benthic biofilms (grazers), fine benthic organic matter (collector‐gatherers), and organic particles suspended in the water column (filter feeders). Stream reaches with guppies also had higher primary productivity and higher N fluxes to grazers and filter feeders. In contrast, N fluxes to collector‐gatherers were reduced in guppy introduction reaches relative to upstream controls. N fluxes to leaf‐shredding invertebrates, predatory invertebrates, and the other fish species present (Hart's killifish, Anablepsoides hartii) did not differ across light or guppy treatments, suggesting that effects on detritus‐based linkages and upper trophic levels were not as strong. Effect sizes of guppy and canopy treatments on N flux rates were similar for most taxa, though guppy effects were the strongest for filter feeding invertebrates while canopy effects were the strongest for collector‐gatherer invertebrates. Combined, these results extend previous knowledge about top‐down and bottom‐up controls on ecosystems by providing experimental, reach‐scale evidence that both pathways can act simultaneously and have equally strong influence on nutrient fluxes from inorganic pools through primary consumers.

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Section: Discussioncontrasting

confidence: 49%

“…), grazing armored catfish (Capps et al. ), or detritivorous fish (Flecker and Taylor , Taylor et al. ), but we noted no effects of guppy presence on biofilm biomass or chlorophyll a standing stock despite increased primary production in guppy reaches.…”

Section: Discussioncontrasting

confidence: 48%

Fish introductions and light modulate food web fluxes in tropical streams: a whole‐ecosystem experimental approach

Collins

Thomas

Heatherly

et al. 2016

Ecology

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“…From a statistical standpoint, A. stamineus’ dietary shift from algal to invertebrate prey was best explained by differences in fish community structure (DC1 community , AIC Table S4). Studies elsewhere show that high densities of non‐native algivorous loricariids (e.g., Hypostomus and Ancistrus armored catfish; Figure a) and omnivorous poeciliids and cichlids (e.g., tilapia) fishes can compete with native species for algal resources in urban streams (e.g., Capps et al., ). The dominance of invasive species across all trophic levels in urban streams of Hawai'i (Figure a, c, Table S4) represents an unnatural appropriation of energy and nutrients that would otherwise have been accessible to native fishes.…”

Section: Discussionmentioning

confidence: 99%

“…Loss of riparian vegetation could also diminish input of allochthonous detritus and terrestrial invertebrates (Richardson, Zhang, & Marczak, 2010). Moreover, invasion of low trophic level exotic species (e.g., snails, armored catfish, tilapia, carp) may accentuate competition for basal resources, including from species that are less vulnerable to predation (Capps, Ulseth, & Flecker, 2015;Vinson & Baker, 2008). Hence, urban stream syndrome may result in reduced basal resources available to support native grazers (Gido & Franssen, 2007;Kautza & Sullivan, 2016;Singer & Battin, 2007).…”

Section: Introductionmentioning

confidence: 99%

Overcoming urban stream syndrome: Trophic flexibility confers resilience in a Hawaiian stream fish

et al. 2018

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Urbanisation is widely associated with a suite of physical, chemical and biological degradation of stream ecosystems, known as “urban stream syndrome.” It is unclear whether urban stream syndrome is applicable to oceanic islands, where marine dispersal of larvae enables diadromous species to continuously recolonise even highly degraded urban streams. The depauperate native fauna of oceanic island streams can be entirely composed of diadromous species, but urban streams food webs are often dominated by introduced predators, competitors and functional groups derived from continental systems. Despite these challenges, some native species appear to thrive in urbanised catchments. Here, we test for urban stream syndrome on oceanic islands by quantifying catchment land use, nutrient concentrations and fish community composition for 37 streams across the Hawaiian archipelago. To assess how native species adapt to food webs altered by species introductions, we quantified trophic responses by examining stomach contents, nitrogen stable isotopes and body condition of Awaous stamineus (an omnivorous goby) in each stream. Urbanisation was consistently associated with nitrogen pollution and replacement of native species with more tolerant exotics. Population densities of three of five native goby species declined sharply with urbanisation, whereas the two other native gobies species were resilient. The trophic position of the omnivore A. stamineus was elevated in urban streams compared to forested catchments, reflecting a shift in stomach contents from algae to greater reliance on exotic aquatic and terrestrial invertebrates. Comparable body condition and resilient population density of A. stamineus across the urbanisation gradient suggest that dietary flexibility buffers this species against environmental degradation. Our findings indicate that the concept of urban stream syndrome is applicable to oceanic islands, yet A. stamineus shows striking resilience. Flexibility in diet, life history and habitat use of this native goby appear to buffer it against the effects of urbanisation compared to most other amphidromous fishes in Hawaiian streams.

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“…We examined the direct effects of loricariid grazing on algal biomass and stoichiometry. However, in other work in the Chacamax River, investigators have documented a strong positive effect of loricariid remineralization on algal biomass and GPP (Capps et al 2014). Therefore, the potential influence of loricariid remineralization on the patterns we documented should be recognized.…”

Section: Discussionmentioning

confidence: 62%

High impact of low-trophic-position invaders: nonnative grazers alter the quality and quantity of basal food resources

Capps

Flecker

2015

Freshwater Science

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Low-trophic-position animals, such as herbivorous and detritivorous fishes, mollusks, and crustaceans, have been introduced and become established in aquatic ecosystems throughout the globe. After introduction, they have the potential to change community structure and ecosystem processes fundamentally. Armored catfishes (Siluriformes:Loricariidae) are grazing fishes that have an extensive nonnative distribution. High population densities of nonnative loricariids have been linked to the decline of freshwater fisheries in invaded habitats, but the mechanisms underlying declines are poorly understood. We coupled the results of 2 loricariid exclosure experiments with a comparison of invaded and uninvaded sites to measure the effects of loricariids on the quantity and quality of food resources in a tropical stream. Loricariid grazing reduced the standing stock of benthic organic matter and algal biomass in experimental manipulations and in the site comparison. Moreover, grazing by loricariids significantly altered the stoichiometry and the total amount of C, N, and P stored in the epilithon. The effects on P were particularly strong. Our results indicate that high densities of low-trophicposition invaders can significantly reduce the quality and the quantity of food resources in invaded systems. In particular, our findings provide evidence that the invasion of a P-rich grazer in a P-limited system has the potential to reduce P availability for other consumers.

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Quantifying the top-down and bottom-up effects of a non-native grazer in freshwaters

Cited by 22 publications

References 57 publications

Fish introductions and light modulate food web fluxes in tropical streams: a whole‐ecosystem experimental approach

Fish introductions and light modulate food web fluxes in tropical streams: a whole‐ecosystem experimental approach

Overcoming urban stream syndrome: Trophic flexibility confers resilience in a Hawaiian stream fish

High impact of low-trophic-position invaders: nonnative grazers alter the quality and quantity of basal food resources

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