Loss of Rare Fish Species from Tropical Floodplain Food Webs Affects Community Structure and Ecosystem Multifunctionality in a Mesocosm Experiment
Leibniz Center for Tropical Marine Ecology, Germany PLoS ONE
(Impact Factor: 3.23).
01/2014; 9(1):e84568. DOI: 10.1371/journal.pone.0084568
Experiments with realistic scenarios of species loss from multitrophic ecosystems may improve insight into how biodiversity affects ecosystem functioning. Using 1000 L mesocoms, we examined effects of nonrandom species loss on community structure and ecosystem functioning of experimental food webs based on multitrophic tropical floodplain lagoon ecosystems. Realistic biodiversity scenarios were developed based on long-term field surveys, and experimental assemblages replicated sequential loss of rare species which occurred across all trophic levels of these complex food webs. Response variables represented multiple components of ecosystem functioning, including nutrient cycling, primary and secondary production, organic matter accumulation and whole ecosystem metabolism. Species richness significantly affected ecosystem function, even after statistically controlling for potentially confounding factors such as total biomass and direct trophic interactions. Overall, loss of rare species was generally associated with lower nutrient concentrations, phytoplankton and zooplankton densities, and whole ecosystem metabolism when compared with more diverse assemblages. This pattern was also observed for overall ecosystem multifunctionality, a combined metric representing the ability of an ecosystem to simultaneously maintain multiple functions. One key exception was attributed to time-dependent effects of intraguild predation, which initially increased values for most ecosystem response variables, but resulted in decreases over time likely due to reduced nutrient remineralization by surviving predators. At the same time, loss of species did not result in strong trophic cascades, possibly a result of compensation and complexity of these multitrophic ecosystems along with a dominance of bottom-up effects. Our results indicate that although rare species may comprise minor components of communities, their loss can have profound ecosystem consequences across multiple trophic levels due to a combination of direct and indirect effects in diverse multitrophic ecosystems.
Available from: Edson Fontes Oliveira
- "The detection of these patterns allows the possibility of a more precise conservation plan for the area, defining the priorities in detail. The fish fauna of freshwater ecosystems have suffered directly from the impacts associated with urban population growth (Pendleton et al. 2014). Other factors such as the introduction of exotic species (Vitule 2012), pollution and deforestation (Carvalho et al. 2012), busbaraquatic ecosystems (Burns et al. 2006, Barletta et al. 2010), and predatory fishing have contributed significantly to the decline in species richness. "
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ABSTRACT: Studies that organize lists of species are essential and act as the starting point for future discussions on the ecology of fish in environments that are poorly studied. The present paper describes the fish assemblage of the hydrographic basin of Chasqueiro Stream, an important component of the Mirim Lagoon system. Fish were collected during one year period between August/2012 and July/2013 in six sites, comprising three biotopes: upstream, reservoir and downstream. A total of 22,853 specimens were collected, and were distributed into 83 species, 20 families, and eight orders. The two species with the largest number of individuals captured were Bryconamericus iheringii with 2,904 (12.71%) and Cheirodon ibicuiensis with 2,868 (12.55%). Characiformes and Siluriformes were the most representative orders in terms of richness and abundance. Bryconamericus iheringi and Cyanocharax alburnus were the species with the highest abundance upstream, while Hyphessobrycon luetkenii and Corydoras paleatus contributed more to the abundance downstream. Cheirodon ibicuhiensis and Heterocheirodon jacuhiensis were the most representative species in the reservoir. This study revealed a rich fauna of fish, which should be preserved for future generations and for the maintenance of local and regional biodiversity.
Available from: Carolina Lima
- "They lower the diversity of structural features preferred by fish and other aquatic organisms and disrupt longitudinal connectivity, which are translated into biodiversity losses (Bunn and Arthington, 2002; Poff and Zimmerman, 2010; Webb et al., 2013). Recent studies have shown a link between local species loss and changes in ecosystem functioning (Balvanera et al., 2006; Cardinale et al., 2006; Taylor et al., 2006; Pendleton et al., 2014). Ecological consequences of damming are especially alarming for tropical regions where many large rivers have been modified to some extent by large hydroelectric dams (Araújo et al., 2013), and the construction of many more are expected (Marques et al., 2009). "
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ABSTRACT: Neotropical freshwaters host some of the most biodiverse ecosystems in the world and are among the most threatened by habitat alterations. The high number of species and lack of basic ecological knowledge provide a major obstacle to understanding the effects of environmental change. We assessed the impact of dam closure on the fish communities of a neotropical river by applying simple descriptions of community organizations: Species Abundance Distribution (SAD) and Abundance Biomass Comparison (ABC) curves. Fish data were collected using gillnets during three distinct time periods (one year before, one year after and five years after dam closure), at eight sites located downstream of the dam, in the reservoir, transition zone and upstream. A total of 69343 individuals representing 260 species were recorded. Dam closure was associated with changes in the organization of fish communities at all sites. Species richness tended to increase immediately after dam closure while evenness decreased. Changes in taxonomic structure (richness and evenness) were accompanied by a change in the distribution of biomass with the proportionate contribution by smaller individuals significantly increased relative to larger individuals. Five years on, richness had fallen to below pre-closure levels at all sites, while the comparative stability of assemblages in the transformed habitats was reflected by biomass-abundance distribution patterns that approximated pre-disturbance ratios. This simplistic analysis provided a sensitive and informative assessment of ecological conditions that highlights the impact to ecosystem process and ecological networks and has particular value in regions where a lack of detailed ecological knowledge precludes the application of traditional bioassessment methods. This article is protected by copyright. All rights reserved.
Available from: Santiago Soliveres
- "The M-index is statistically robust (Maestre et al., 2012), is being increasingly used (e.g. Pendleton et al., 2014; Wagg et al., 2014) and is related to other widely used multifunctionality metrics (Byrnes et al., 2014). Multifunctionality measurements may obscure specific responses for the different soil variables measured. "
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ABSTRACT: The global spread of woody plants into grasslands is predicted to increase over the coming century. While there is general agreement regarding the anthropogenic causes of this phenomenon, its ecological consequences are less certain. We analyzed how woody vegetation of differing cover affects plant diversity (richness and evenness) and multiple ecosystem functions (multifunctionality) in global drylands, and how this changes with aridity.
224 dryland sites from all continents except Antarctica widely differing in their environmental conditions (from arid to dry-subhumid sites) and woody covers (from 0 to 100%).
Using a standardized field survey, we measured the cover, richness and evenness of perennial vegetation. At each site, we measured 14 ecosystem functions related to soil fertility and the build-up of nutrient pools. These functions are critical for maintaining ecosystem function in drylands.
Species richness and ecosystem multifunctionality were strongly influenced by woody vegetation, with both variables peaking at relative woody covers (RWC) of 41-60%. This relationship shifted with aridity. We observed linear positive effects of RWC in dry-subhumid sites. These positive trends shifted to hump-shaped RWC-diversity and multifunctionality relationships under semiarid environments. Finally, hump-shaped (richness, evenness) or linear negative (multifunctionality) effects of RWC were found under the most arid conditions.
Plant diversity and multifunctionality peaked at intermediate levels of woody cover, although this relationship became increasingly positive under wetter environments. This comprehensive study accounts for multiple ecosystem attributes across a range of woody covers and environmental conditions. Our results help us to reconcile contrasting views of woody encroachment found in current literature and can be used to improve predictions of the likely effects of encroachment on biodiversity and ecosystem services.
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