Multiple trophic groups regulate the functioning of tropical shallow lakes

Moi, D; Romero, Gustavo Q.; Antiqueira, Pablo; Mormul, Roger Paulo; Teixeira de Mello, Franco; Bonecker, Claudia

Lake in Brazil

Human activities influence virtually all ecosystems around the globe, which has caused loss of trophic groups (trophic groups are defined as group of organisms within an ecosystem that occupy the same level in a food web) of the ecosystems in intensity never before recorded. Despite this, the importance of multiple trophic groups (that is, multitrophic diversity) in maintaining multiple ecosystem functions (that is, multifunctionality) remains unclear, especially in highly diverse aquatic ecosystems where studies are lacking. This represents a critical knowledge gap, taking into account the increasing loss of trophic groups at a global scale. Thus, understanding how different trophic groups influences multifunctionality is crucial to better predict the ecological consequences of the loss of trophic groups. For the first time, we studied how the richness of multiple trophic groups influence the functioning of highly diverse aquatic ecosystems. We used 16 years database from three highly diverse tropical shallow lakes, which included nine different trophic  groups (for example, vertebrate predators, herbivorous, detritivorous, and omnivorous, besides primary producers, small-size filter feeders, small omnivorous carnivores, phagotrophic protists, and invertebrate omnivorous) and 14 ecosystem functions, such as phosphorus available, nitrogen available, percentage of dissolved oxygen, organic matter available, chlorophyll-a of phytoplankton, chlorophyll-a of periphyton, biomass of piscivorous, omnivorous-invertivorous, detritivorous, and herbivorous, and abundance of Amoeba testacea, rotifera, microcrustacean, and chironomidae. We would like to understand how the richness of single trophic groups and multitrophic richness affect multifunctionality. We also wanted to know the consequences of the loss of any trophic groups to ecosystem multifunctionality, and how interactions among trophic groups influence multifunctionality.

We found that all trophic groups are important to maintain the functioning of highly diverse tropical shallow lakes, and thus, loss of any trophic group could impair multifunctionality of these lakes. We also found that the richness of trophic groups comprised of large-size species (for example, vertebrate carnivores) have a stronger positive influence on multifunctionality, but the richness of trophic groups composed of small-size species (for example, invertebrate omnivorous) is vital in fueling large size trophic groups. As we expected, the richness across multiple trophic groups is vital for the sustaining the integrity and functioning of highly diverse aquatic ecosystems. Finally, we highlight that link between multitrophic richness and multifunctionality is not limited to terrestrial ecosystems and it can be also applied to highly diverse aquatic ecosystems.

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