Productivity, Disturbance and Ecosystem Size Have No Influence on Food Chain Length in Seasonally Connected Rivers

Warfe, Danielle M.; Jardine, Timothy D.; Pettit, Neil E.; Hamilton, Stephen K.; Pusey, Bradley James; Bunn, Stuart E.; Davies, Peter M.; Douglas, Michael M.

doi:10.1371/journal.pone.0066240

Cited by 46 publications

(62 citation statements)

References 86 publications

(184 reference statements)

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“…We found that resource availability can explain 60 % of the FCL variation in our studied subtropical rivers, consistent with findings on neotropical (Hoeinghaus et al 2008) and temperate (Thompson and Townsend 2005) rivers. A previous research on Australian wet-dry tropical rivers used nutrient concentration as a measure of productivity, but the results could not explain the relationship between resource availability and FCL (Warfe et al 2013). In the present study, we found that resource availability increased as the river basin area increased and that fish species richness was also positively related to resource availability.…”

Section: Discussioncontrasting

confidence: 93%

“…Although productivity generally increases FCL (Thompson and Townsend 2005;Hoeinghaus et al 2008;Doi 2012), the effects of the magnitude of ecosystem size could positively (Post et al 2000;Takimoto et al 2008;Doi et al 2009;McHugh et al 2010;Sabo et al 2010) or neutrally (Thompson and Townsend 2005;Warfe et al 2013) influence FCL. Furthermore, the effects of disturbance on FCL are highly variable and could be positive (Calizza et al 2012), neutral (Walters and Post 2008;Warfe et al 2013), or even negative (McHugh et al 2010;Sabo et al 2010).…”

Section: Introductionmentioning

confidence: 98%

“…By contrast, Calizza et al (2012) found that the effect of flood disturbance on urban river FCL in Rome varies at different timescales: The increase in mean FCL was short term because of the effect of urbanization on the food web structure. Warfe et al (2013) reported that resource availability, disturbance, and ecosystem size have no influence on the FCLs of seasonally connected northern Australian rivers. These rivers exhibited a distinct seasonal hydrology.…”

Section: Introductionmentioning

confidence: 99%

“…These rivers exhibited a distinct seasonal hydrology. Periodic flooding was proposed to facilitate predatory fish movement, which links isolated food webs and potentially creates a regional food web that could override the local effects of productivity, disturbance, and ecosystem size (Warfe et al 2013). Therefore, while good progress has been made in understanding how these three hypotheses are important under varying contexts, more work is needed to refine our understanding of when and how each of these factors determines FCL.…”

Section: Introductionmentioning

confidence: 99%

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Resource availability determines food chain length in Chinese subtropical rivers

Wang

Xiao

et al. 2016

Aquat Ecol

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Three prevailing hypotheses, namely resource availability, ecosystem size, and disturbance, are often used to explain variations in food chain length (FCL). Rivers vary widely in size, resources, and disturbance dimensions, even within the same catchment, providing an ideal platform to test ecological drivers of FCL in aquatic systems. In this study, we tested how resource availability (indicated by macroinvertebrate biomass), ecosystem size (indicated by basin area), and disturbance (indicated by daily water-level coefficients of variation) affected stable isotope-based estimates of FCL in subtropical rivers in the Province Jiangxi, China. The FCL varied widely among the studied rivers with a mean of 3.09 (range 2.00-3.99). Model-selection results indicated that resource availability could explain 60 % of the observed variation in FCL. The FCL of the studied rivers was positively correlated with fish richness and the total area of fish community d 13 C-d 15 N bi-plot space, thereby indicating that an increase in fish diversity could influence the trophic structure within the food web and lead to a longer FCL. Taken together, our results suggest that resource availability could predict FCL in subtropical rivers and plays a significant role in maintaining longer FCLs by providing more energy to support upper trophic-level fishes.

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Section: Discussioncontrasting

confidence: 93%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Resource availability determines food chain length in Chinese subtropical rivers

Wang

Xiao

et al. 2016

Aquat Ecol

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“…Previous studies have found conflicting effects of ecosystem size, productivity, and disturbance on food-chain length (Takimoto and Post 2013; Warfe et al. 2013). However, in most studies, the identity of the top predator has changed across these gradients.…”

Section: Introductionmentioning

confidence: 99%

Lake size and fish diversity determine resource use and trophic position of a top predator in high‐latitude lakes

Eloranta

Kahilainen

Amundsen

et al. 2015

Ecology and Evolution

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Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes covering a marked gradient in size (0.5–1084 km2) and fish species richness (2–13 species). We expected top predators to shift from littoral to pelagic energy sources with increasing lake size, as the availability of pelagic prey resources and the competition for littoral prey are both likely to be higher in large lakes with multispecies fish communities. We also expected top predators to occupy a higher trophic position in lakes with greater fish species richness due to potential substitution of intermediate consumers (prey fish) and increased piscivory by top predators. Based on stable carbon and nitrogen isotope analyses, the mean reliance of Arctic charr on littoral energy sources showed a significant negative relationship with lake surface area, whereas the mean trophic position of Arctic charr, reflecting the lake food-chain length, increased with fish species richness. These results were supported by stomach contents data demonstrating a shift of Arctic charr from an invertebrate-dominated diet to piscivory on pelagic fish. Our study highlights that, because they determine the main energy source (littoral vs. pelagic) and the trophic position of generalist top predators, ecosystem size and fish diversity are particularly important factors influencing function and structure of food webs in high-latitude lakes.

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River food chains lead to riparian bats and birds in two mid‐order rivers

Jackson¹,

Stock²,

Harris

et al. 2020

Ecosphere

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River regulation can modify natural flow regimes with deleterious effects on aquatic communities. While the effects of flow manipulation on the physical environment and populations and assemblages of aquatic organisms have been described thoroughly, how and to what extent river regulation influences ecosystem processes like food web architecture is less studied. Emergent aquatic insect prey can provide an important food resource to riparian consumers like birds and bats with concomitant consequences for nutrient cycling through aquatic-terrestrial food webs, thus potentially increasing the spatial influence of river regulation into the riparian zone and beyond. We used naturally abundant stable isotopes of carbon and nitrogen to compare food web architecture (trophic position and reliance on an aquatic nutritional pathway) leading to birds and bats between a regulated river, the Tuolumne River downstream of Hetch Hetchy Reservoir, and an adjacent unregulated river, the Merced River, located in Yosemite National Park on the west slope of the Sierra Nevada, California, USA. We found that both birds and bats derived >50% of their nutrition from food webs originating in photosynthesis by algae. In addition, birds and bats occupied a similar trophic position to predatory fish in other systems. Both birds and bats seemed to rely more strongly on an aquatic nutritional pathway during the dryer year of our study period, underscoring the potential importance of emergent aquatic prey as a water subsidy in dry systems and in dry years. In the Tuolumne River, reservoir managers strive to simulate characteristics of the natural flow regime, including seasonal scouring flows and prolonged floodplain inundation. Although we found no conclusive evidence of an effect of river regulation on food web responses, our study suggests that nutrient cycling through aquatic-terrestrial food webs expands the potential influence of river regulation to organisms and ecosystems typically characterized as terrestrial.

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Productivity, Disturbance and Ecosystem Size Have No Influence on Food Chain Length in Seasonally Connected Rivers

Cited by 46 publications

References 86 publications

Resource availability determines food chain length in Chinese subtropical rivers

Resource availability determines food chain length in Chinese subtropical rivers

Lake size and fish diversity determine resource use and trophic position of a top predator in high‐latitude lakes

River food chains lead to riparian bats and birds in two mid‐order rivers

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