Experimental test of the ecosystem impacts of the keystone predator Triops cancriformis (Branchiopoda: Notostraca) in temporary ponds

Abstract

Summary Keystone species can influence an ecosystem through a series of trophic (both direct and indirect) and non‐trophic effects. In temporary ponds, tadpole shrimps were recently identified as keystone predators, but the full extent of their ecosystem impact is still poorly known. Using a large‐scale mesocosm experiment, we quantified the impact of different Triops cancriformis densities on ecosystem properties: water quality (including chlorophyll a as measure for phytoplankton biomass) and the diversity and structure of macrophyte and zooplankton communities. Mesocosms of 400 L (1 m2 surface) were lined with natural pond sediment of two study ponds differing in their natural Triops densities (Triops‐rich and Triops‐poor pond) and inundated to allow hatching from the egg bank. Afterwards, four Triops density treatments were established in the mesocosms: 0 (control), 5, 25 and 100 Triops per m2. After 13 weeks, the two highest Triops densities significantly influenced the ecosystem functioning not only by triggering changes in the diversity and composition of the pond communities but also by affecting water quality through bioturbation. These results confirm that tadpole shrimp can function as ecosystem engineers in temporary ponds and could promote a shift from a clear water to a turbid state through a series of trophic and non‐trophic level effects.

Livestock disturbances in Mediterranean temporary ponds: A mesocosm experiment with sheep manure and simulated trampling

“…This may have a positive effect on smaller fragile species with poor competitive abilities, as found with the rare pillwort Pilularia minuta (Bouahim et al., ). Lastly, it must be noted that R. baudotii , a deeply rooted tolerant species in Triops ‐disturbed mesocosms (Croel & Kneitel, ; Waterkeyn et al., ) flourished in undisturbed conditions in our study. This illustrates that intense grazing disturbance can even affect robust species during the germination process.…”

“…Copepods are known to be fast swimmers avoiding hydrodynamic disturbances and they cope well with turbid conditions (Buskey, Lenz, & Hartline, ), while Triops is able to thrive in highly turbid environments (Waterkeyn et al., ) in which predation by birds is less likely. Additionally, Triops may prey on smaller organisms and further increase turbidity due to its foraging behaviour (Boix, Sala, Gascón, & Brucet, ; Croel & Kneitel, ; Waterkeyn et al., ), reducing hatching taxon richness even further. Intermediate sized branchiopods, such as anostracans and spinicaudatans, as well as Daphnia hispanica , were not significantly affected by disturbance.…”

“…Negative effects of crustaceans and algae on macrophyte cover and richness have been documented previously (Croel & Kneitel, 2011a,b;Kneitel & Lessin, 2010;Waterkeyn, Grillas, & Brendonck, 2016). To assess the potential contribution of these effects on both macrophyte richness and cover, a generalised estimating equation (γ distribution with log link) was conducted which used treatments as fixed factors and Triops density, cyanobacteria density, filamentous algae cover, and chlorophyll-a as covariates.…”

“…Triops is able to thrive in highly turbid environments (Waterkeyn et al, 2016) in which predation by birds is less likely. Additionally, Triops may prey on smaller organisms and further increase turbidity due to its foraging behaviour (Boix, Sala, Gascón, & Brucet, 2006;Croel & Kneitel, 2011b;Waterkeyn et al, 2016), reducing hatching taxon richness even further. Intermediate sized branchiopods, such as anostracans and spinicaudatans, as well as Daphnia hispanica,…”

Global Patterns of Aquatic Macroinvertebrate Dispersal and Functional Feeding Traits in Aridland Rock Pools

“…In addition to hydroperiod disrupting passive disperser life cycles, increased prevalence of active dispersing predators may further modify local communities. In fact, predation may be nearly as strong of a community filter as hydroperiod (Jocqué et al, 2010b), because predators have the capacity to shape the primary consumer communities through prey selection (Dodson, 1987;Kubly, 1992;Blaustein et al, 1995;Anderson et al, 1999;Jocqué et al, 2007;Waterkeyn et al, 2016).…”