Loss of Rare Fish Species from Tropical Floodplain Food Webs Affects Community Structure and Ecosystem Multifunctionality in a Mesocosm Experiment

Abstract

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.

Ichthyofauna of the hydrographic basin of the Chasqueiro Stream (Mirim Lagoon system, southern Brazil): generating subsidies for conservation and management

“…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 , Barletta et al 2010, and predatory fishing have contributed significantly to the decline in species richness.…”

Functional Rarity: The Ecology of Outliers

“…Rare species perform different functions in ecosystems, some being redundant with those of many other rare and common species while some are unique [10][11][12][13]. Surprisingly, few studies have investigated the rarity of functions (functional rarity hereafter) within communities and its importance for the functioning of ecosystems [12,14,15].…”

“…Growing consensus suggests that BEF relationships are driven by the diversity of functions carried out by species and their individuals within an ecosystem [27][28][29]. In parallel, the disproportionate effect of some rare species (for example, keystone species) on ecosystem processes is increasingly reported [12,15,30]. This calls for a deeper integration of functional rarity in BEF studies particularly to meet the challenge of maintaining multiple processes under global changes [31].…”

Trophic relationships in fish assemblages of Neotropical floodplain lakes: selectivity and feeding overlap mediated by food availability

“…Trophic interactions in food chains in these systems have received increased attention in recent decades, and constitute an effi cient approach for improved understanding of the structure of aquatic communities (Polis & Winemiller, 1996;Petchey et al, 2010;Downing et al, 2014;Pendleton et al, 2014;Binzer et al, 2015).…”