Feeding by omnivores increases food available to consumers

Iwai, Noriko; Kagaya, Takashi; Alford, Ross A.

doi:10.1111/j.1600-0706.2011.20128.x

Cited by 19 publications

(11 citation statements)

References 49 publications

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“…First, there is little information on how tadpoles are affected by algal stoichiometric variation as mediated by light and nutrients (but see Liess et al ). This is surprising, given that many amphibian species are of conservation concern (Semlitsch ), and that limited existing data suggests that tadpoles can affect primary production and nutrient flux in aquatic ecosystems (Seale , Iwai and Kagaya , Connelly et al , Iwai et al ). Second, we reasoned that it would be more tractable to quantify benthic consumer production using an animal that would not emerge or metamorphose during our experiment (such as most herbivorous aquatic insects).…”

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confidence: 99%

Light and nutrients regulate energy transfer through benthic and pelagic food chains

Rowland

Bricker

Vanni

et al. 2015

Oikos

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The amount of energy flowing to top trophic levels depends on primary production and the efficiency at which it is converted to production at each trophic level. In aquatic systems, algal production is often limited by light and nutrients, and the nutritional quality of algae depends on the relative balance of these two resources. In this study, we used a mesocosm experiment to examine how light and nutrient variation affected food chain efficiency (FCE, defined as the proportion of primary production converted to top trophic level production), using a food web with benthic and pelagic food chains. We also related variation in benthic and pelagic efficiencies to the nutritional quality of primary producers, i.e. carbon:nitrogen:phosphorus stoichiometry. As predicted, pelagic and benthic FCEs were highest under low light/high nutrient conditions, the treatment with the best algal food quality, i.e. the lowest C:nutrient ratios. Pelagic FCE and pelagic herbivore efficiency (HE P ) were more responsive than benthic FCE to variation in light and nutrients. Furthermore, pelagic FCE and HE P were highly correlated with algal C:P, suggesting 'carryover effects' of algal food quality on carnivores (larval fish) via effects on herbivore (zooplankton) quality. Benthic (tadpole) production was primarily explained by primary production rate, suggesting food quantity rather than quality drives their production. However, benthic FCE was also highest at low light/high nutrients and was significantly correlated with food quality. The stronger effect of food quality in mediating pelagic compared to benthic efficiencies, is consistent with differences in the stoichiometric mismatches between algae and consumers. Pelagic FCE and HE P were more likely to be P-limited, whereas benthic FCE was more likely N-limited. This study is the first to examine both pelagic and benthic FCE within the same system, and highlights the importance of differential consumer needs in determining how food quality affects energy transfer efficiency.

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confidence: 99%

Light and nutrients regulate energy transfer through benthic and pelagic food chains

Rowland

Bricker

Vanni

et al. 2015

Oikos

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“…This methodological approach is consistent with similar studies on food consumption in Canada Iwai, Kagaya and Alford, 2012). The survey was made available online (including posted on social media outlets) and invitations were widely distributed across the country to several regions and socio-economic groups, to ensure various regional and demographic groups were represented in the findings.…”

Section: Methodsmentioning

confidence: 82%

Pre-Shopping Habits and Consumer Vulnerability in Food Retailing

Charlebois¹,

Chamberlain²,

Herian³

2018

JFR

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Food prices in Canada have reached uncharacteristic highs in the last two years. Seven-dollar heads of cauliflower in 2016 became the poster-vegetable of the costs of food prices and questions arose about how Canadian consumers were assessing and mitigating their vulnerability. This study surveyed just over 1000 Canadians in all regions of Canada, including the North, to assess perceived vulnerability of Canadian consumers to rises in food prices and determine the behavioural changes that occurred to mitigate vulnerability. We found that Canadians generally felt more vulnerable to fluctuating food prices and that certain demographic traits, such as age, income, geographic location, and family status did have an impact on degree of vulnerability and what methods consumers would use to try to adapt to price volatility. Some consumer groups were more vulnerable than others, but consumers demonstrated awareness of and ability to adapt to changes in food prices over time.

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“…While it is difficult to predict the exact trophic pathways that the addition of an omnivorous species such as D . villosus will affect (Iwai et al ., ), we suggest that the possibility of greater leaf processing earlier in the season and under warmer conditions could result in changes to the overall community assemblage of invaded ecosystems.…”

Section: Discussionmentioning

confidence: 97%

“…The results from this study highlight how the qualities of invasive species that contribute to colonization success can also cause disruptions to ecosystem processes. While it is difficult to predict the exact trophic pathways that the addition of an omnivorous species such as D. villosus will affect (Iwai et al, 2012), we suggest that the possibility of greater leaf processing earlier in the season and under warmer conditions could result in changes to the overall community assemblage of invaded ecosystems.…”

Section: Exploitation Of a Wide Feeding Nichementioning

confidence: 89%

“…Thus, in systems heavily colonized by D. villosus, shredding effects may be especially elevated at higher temperatures compared with what would have been expected if G. pulex had remained the predominant species. Such an outcome could, in turn, increase available nutrients and contribute to increased production of algae, phytoplankton, and herbivorous macroinvertebrates (Iwai et al, 2012). The extrapolation of a short-term feedback experiment in this way must be treated with caution; although feeding rates were higher at 25 C, it cannot be known for certain how long-term temperature changes will affect growth, metabolism, reproductive output and survivorship of either native or invasive species.…”

Section: Tolerance Of Extreme Environmental Conditionsmentioning

confidence: 99%

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Differential leaf‐litter processing by native (Gammarus pulex) and invasive (Dikerogammarus villosus) freshwater crustaceans under environmental extremes

Truhlar

Dodd

Aldridge

2013

Aquatic Conservation

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There is increasing interest in understanding the implications of biological invasions within the context of ecosystem functioning. Non‐native crustaceans are of particular interest within fresh waters because of their important contributions to leaf‐litter processing. The alien amphipod Dikerogammarus villosus is spreading rapidly through Europe where it has displaced native gammarids including Gammarus pulex. The resultant change in shredder communities has considerable implications for the dynamics of resource availability within invaded systems. The invasive success of D. villosus has been attributed to many characteristics, including its ability to tolerate a wide range of environmental conditions and to exploit a wide feeding niche. These characteristics are thought to give D. villosus an advantage over native species, especially in habitats subject to changing environmental conditions. The leaf (Salix alba) shredding efficiency, defined as the leaf mass consumed over the 4‐day experiment per amphipod‐day, was measured for D. villosus and G. pulex under extreme temperature and conductivity conditions, in single species and mixed species aquaria. At high temperatures (25°C), D. villosus shredded significantly more leaves than size‐matched G. pulex. Conductivity extremes had no species effect; overall leaf‐shredding efficiency was significantly greater at low conductivity (250 μS cm‐1) than high conductivity (1870 μS cm‐1). An inspection of daily leaf disc consumption found that the two species showed significantly different leaf consumption patterns, with D. villosus consuming more leaves earlier in the experiment. These results suggest that D. villosus invasion could lead to ecosystem‐level changes in leaf processing, such as greater leaf processing earlier in autumn and at higher temperatures, which could alter nutrient dynamics and community assemblages within invaded systems. Such effects may not be reflected in biotic indices used to assess ecological status, as these indices do not currently distinguish between native and invasive species in the same family. Copyright © 2013 John Wiley & Sons, Ltd.

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Feeding by omnivores increases food available to consumers

Cited by 19 publications

References 49 publications

Light and nutrients regulate energy transfer through benthic and pelagic food chains

Light and nutrients regulate energy transfer through benthic and pelagic food chains

Pre-Shopping Habits and Consumer Vulnerability in Food Retailing

Differential leaf‐litter processing by native (Gammarus pulex) and invasive (Dikerogammarus villosus) freshwater crustaceans under environmental extremes

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