Do mute swan (Cygnus olor) grazing, swan residence and fishpond nutrient availability interactively control macrophyte communities?

Gayet, Guillaume; Guillemain, Matthieu; Fritz, Hervé; Mesleard, FranÃ§ois; Begnis, ClÃ©ment; Costiou, A.; Body, Guillaume; Curtet, Laurence; Broyer, J.

doi:10.1016/j.aquabot.2011.04.003

Cited by 27 publications

(19 citation statements)

References 32 publications

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“…However, bird herbivory can influence regime shifts in other ways apart from grazing. For example, an effect regularly seen is that grazing birds alter macrophyte species composition, because they prefer certain macrophyte species over others (van Donk & Otte 1996;Hidding et al, 2010;Gayet et al, 2011). Considering different macrophyte species may also be relevant because the exact effect of herbivory may depend on plant traits.…”

Section: Discussionmentioning

confidence: 99%

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes: a model study

et al. 2016

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Shallow lakes have the potential to switch between two alternative stable states: a clear macrophyte-dominated and a turbid phytoplankton-dominated state. Observational and experimental studies show that in some lakes herbivory by birds may severely decrease macrophyte biomass, while in other lakes, the removed biomass by herbivory is compensated by regrowth. These contradictory outcomes might arise because of interplay between top-down control by bird herbivory and bottom-up effects by nutrient loading on macrophytes. Here, we use the ecosystem model PCLake to study top-down and bottom-up control of macrophytes by coots and nutrient loading. Our model predicted that (1) herbivory by birds lowers the critical nutrient loading at which the regime shift occurs; (2) bird impact on macrophyte biomass through herbivory increases with nutrient loading; and (3) improved food quality enhances the impact of birds on macrophytes, thus decreasing the resilience of the clear-water state even further. The fact that bird herbivory can have a large impact on macrophyte biomass and can facilitate a regime shift implies that the presence of waterfowl should be taken into account in the estimation of critical nutrient loadings to be used in water quality management.

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Section: Discussionmentioning

confidence: 99%

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes: a model study

et al. 2016

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“…herbivory), bottom-up (e.g. nutrient availability), and competitive processes on plant abundance and ecosystem primary productivity (Hughes et al, 2004;Gayet et al, 2011;Wood et al, 2012c;Sarneel et al, 2014). Currently, our limited knowledge of multifactorial regulation of primary producers hinders efforts to manage aquatic ecosystems effectively (Chambers et al, 1999;Bakker et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…We did this because different measures of plant abundance, whilst typically correlated, may not always show identical temporal trends in abundance (Wood et al, 2012a) and may not show the same response to herbivory (Gayet et al, 2011); including these could have introduced additional variance and limited our ability to detect changes in plant abundance due to our explanatory factors. We compared plant abundance with and without herbivores at the time of maximal standing crop in the 'without herbivores' treatment, after Wood et al (2012b).…”

Section: Methods (1) Data Collationmentioning

confidence: 99%

Herbivore regulation of plant abundance in aquatic ecosystems

et al. 2016

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Herbivory is a fundamental process that controls primary producer abundance and regulates energy and nutrient flows to higher trophic levels. Despite the recent proliferation of small-scale studies on herbivore effects on aquatic plants, there remains limited understanding of the factors that control consumer regulation of vascular plants in aquatic ecosystems. Our current knowledge of the regulation of primary producers has hindered efforts to understand the structure and functioning of aquatic ecosystems, and to manage such ecosystems effectively. We conducted a global meta-analysis of the outcomes of plant-herbivore interactions using a data set comprised of 326 values from 163 studies, in order to test two mechanistic hypotheses: first, that greater negative changes in plant abundance would be associated with higher herbivore biomass densities; second, that the magnitude of changes in plant abundance would vary with herbivore taxonomic identity. We found evidence that plant abundance declined with increased herbivore density, with plants eliminated at high densities. Significant between-taxa differences in impact were detected, with insects associated with smaller reductions in plant abundance than all other taxa. Similarly, birds caused smaller reductions in plant abundance than echinoderms, fish, or molluscs. Furthermore, larger reductions in plant abundance were detected for fish relative to crustaceans. We found a positive relationship between herbivore species richness and change in plant abundance, with the strongest reductions in plant abundance reported for low herbivore species richness, suggesting that greater herbivore diversity may protect against large reductions in plant abundance. Finally, we found that herbivore-plant nativeness was a key factor affecting the magnitude of herbivore impacts on plant abundance across a wide range of species assemblages. Assemblages comprised of invasive herbivores and native plant assemblages were associated with greater reductions in plant abundance compared with invasive herbivores and invasive plants, native herbivores and invasive plants, native herbivores and mixed-nativeness plants, and native herbivores and native plants. By contrast, assemblages comprised of native herbivores and invasive plants were associated with lower reductions in plant abundance compared with both mixed-nativeness herbivores and native plants, and native herbivores and native plants. However, the effects of herbivore-plant nativeness on changes in plant abundance were reduced at high herbivore densities. Our mean reductions in aquatic plant abundance are greater than those reported in the literature for terrestrial plants, but lower than aquatic algae. Our findings highlight the need for a substantial shift in how biologists incorporate plant-herbivore interactions into theories of aquatic ecosystem structure and functioning. Currently, the failure to incorporate top-down effects continues to hinder our capacity to understand and manage the ecological dynamics of habitats ...

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“…growth rate, age, competitiveness, anti-herbivore defences) and environmental factors (e.g. water depth, light, temperature, CO 2 availability; Bornette & Puijalon, 2011;Gayet et al, 2011b).…”

Section: Waterfowl Size and Herbivorous Dietmentioning

confidence: 99%

The impact of waterfowl herbivory on plant standing crop: a meta-analysis

et al. 2012

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previous studies have considered waterfowl species as homologous, despite large differences in body mass, our results suggest that species body mass is a key determinant of waterfowl impact on plant standing crop.To examine relative impacts of waterfowl groups based on species body mass, a measure of plant biomass reduction (R s ) per bird per hectare was calculated for each group. Comparison of R s values indicated some differences in impact between different waterfowl groups, with swans having a greater per capita impact than smaller-bodied waterfowl groups. We present evidence that this difference is linked to disparities in individual body size and associated differences in intake rates, diet composition and energy requirements.Future research priorities are proposed, particularly the need for experiments that quantify the importance of factors that determine the magnitude of waterfowl impacts on plant standing crop.

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Do mute swan (Cygnus olor) grazing, swan residence and fishpond nutrient availability interactively control macrophyte communities?

Cited by 27 publications

References 32 publications

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes: a model study

The impact of bird herbivory on macrophytes and the resilience of the clear-water state in shallow lakes: a model study

Herbivore regulation of plant abundance in aquatic ecosystems

The impact of waterfowl herbivory on plant standing crop: a meta-analysis

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