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37
Biodiversity, ecosystem functioning and food webs in freshwaters: assembling the jigsaw puzzle
- Freshwater Biology
, 2009
"... 1. Dramatic advances have been made recently in the study of biodiversity–ecosystem functioning (B-EF) relations and food web ecology. These fields are now starting to converge, and this fusion has the potential to improve our understanding of how environmental stressors modulate ecosystem processes ..."
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1. Dramatic advances have been made recently in the study of biodiversity–ecosystem functioning (B-EF) relations and food web ecology. These fields are now starting to converge, and this fusion has the potential to improve our understanding of how environmental stressors modulate ecosystem processes and the supply of ‘goods and services’. 2. Food web structure and dynamics can exert particularly strong influences on B-EF relations in fresh waters, as consumer–resource interactions (e.g. trophic cascades) are often more important than horizontal interactions within trophic levels. For instance, many freshwater food webs are size structured, with large organisms tending to occupy the higher trophic levels and often exerting powerful effects on ecosystem processes. However, because they are also vulnerable to perturbations, non-random losses of these large taxa can alter both food web structure and ecosystem functioning profoundly. 3. Recently, the focus of food web research has shifted away from exploring patterns, towards developing an understanding of processes (e.g. quantifying fluxes of individuals, biomass, energy, nutrients) and how the two interact. Many of the best-characterized food webs are from fresh waters, and these ecosystems are now being used to address some of the shortcomings of earlier B-EF studies. I have identified several key gaps in our current knowledge and highlighted potentially fruitful avenues of future B-EF and food web research. 4. A major challenge for this newly emerging research is to place it within a unified theoretical framework. The application of metabolic theory and ecological stoichiometry may help to achieve this goal by considering biological systems within the constraints imposed upon them by physical and chemical laws.
Biodiversity, Species Interactions and Ecological Networks in a Fragmented World
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Irreplaceability of river networks: towards catchment-based conservation planning
- Journal of Applied Ecology
, 2008
"... Summary 1. This study has adapted a complementarity-based area-selection method to estimate conservation value/irreplaceability for river systems. Irreplaceability represents the likelihood that an area will be required as part of a conservation system that achieves all conservation targets. We ada ..."
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Summary 1. This study has adapted a complementarity-based area-selection method to estimate conservation value/irreplaceability for river systems. Irreplaceability represents the likelihood that an area will be required as part of a conservation system that achieves all conservation targets. We adapt this measure -often used in marine or terrestrial planning -to consider whole-of-catchment protection in a riverine setting. 2. After dividing the Australian state of Victoria into 1854 subcatchments, we successfully modelled distributions of 400 benthic macroinvertebrate taxa using generalized additive models. We calculated the minimum area required to protect all taxa using three different heuristic selection algorithms. The algorithms were modified to consider the entire upstream catchment for any subcatchment. 3. A summed rarity algorithm, corrected for upstream area, proved to be the most efficient, requiring 100 000 hectares less total catchment area to represent all taxa than the second most efficient algorithm. We calculated irreplaceability by running the algorithm 1000 times and randomly removing 90% of the catchments in each run. From this analysis, we estimated two metrics: Fs (the frequency of selection) and average c (average contribution to conservation targets). 4. Four groups of catchments were identified: (i) catchments that have high contributions and are always or very frequently selected; (ii) catchments that have high contributions and are infrequently selected; (iii) catchments that are always or very frequently selected but contribute few taxa; and (iv) catchments that are infrequently selected and contribute few taxa. 5. Synthesis and applications . For the first time, a complementarity-based algorithm has been adapted to a riverine setting. This algorithm acknowledges the connected nature of rivers by considering not only the local assemblages, but also upstream areas that need to be protected. We demonstrated that using standard algorithms in these connected systems would lead to two mistakes, namely: (i) not all taxa would be covered by reserves that were buffered from potential human disturbances upstream; and (ii) the standard algorithms would not lead to the most efficient solution, potentially costing additional millions of dollars to any conservation scheme. We therefore recommend the use of our algorithm or a similar riverine adaptation of reserve design algorithms to ensure adequate and efficient conservation planning.
Consumer growth linked to diet and RNA-P stoichiometry: Response of Bosmina to variation in riverine food resources
"... Feeding experiments were performed with riverine Bosmina to investigate how their somatic growth rate responded to variation in food resources arising from changing hydrodynamic conditions. Experimental manipulations of food quality and quantity were achieved by diluting riverine suspended particula ..."
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Feeding experiments were performed with riverine Bosmina to investigate how their somatic growth rate responded to variation in food resources arising from changing hydrodynamic conditions. Experimental manipulations of food quality and quantity were achieved by diluting riverine suspended particulate matter (seston) to obtain a range of food concentrations and by amending natural seston with laboratory-grown Scenedesmus acutus. Bosmina experienced food limitation during periods of elevated discharge when the P content of seston was low (C: P. 600). Growth rates covaried with body RNA and P contents (R2 5 0.96 and 0.86, respectively; content expressed as percent of dry mass), which is consistent with the hypothesis that high growth rates require increased allocation to P-rich ribosomal RNA and that high seston C: P induces P limitation in riverine Bosmina. P limitation arises in riverine consumers of riverine seston when hydrologic conditions favor terrestrial inputs, sediment resuspension, and low algal productivity, thereby resulting in seston fractions dominated by P-poor materials. During low discharge, riverine seston was P-rich relative to Bosmina requirements and growth rates were decoupled from body P content. Bosmina RNA content was strongly and linearly related to growth over a broad range of resource conditions, suggesting that it may be a useful surrogate to assess dietary sufficiency of food resources in natural settings.
Testing the response of macroinvertebrate functional structure and biodiversity to flooding
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Universidad de Costa Rica
"... How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System ..."
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How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System
Date defended: _______________
"... ii The Dissertation Committee for Teresa M. Carroll certifies that this is the approved version of the following dissertation: ..."
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ii The Dissertation Committee for Teresa M. Carroll certifies that this is the approved version of the following dissertation:
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"... Spatial heterogeneity of trophic pathways in the invertebrate community of a temperate bog ..."
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Spatial heterogeneity of trophic pathways in the invertebrate community of a temperate bog
