Predator complementarity dampens variability of phytoplankton biomass in a diversity-stability trophic cascade

Abstract

24The indirect effects of top predators on the biomass of lower trophic levels have been 25 extensively documented, especially in aquatic ecosystems and are commonly characterized as 26 "trophic cascades." There have also been studies showing that predator diversity can play an 27 important role in mediating these trophic cascades. In addition, some studies have demonstrated 28 that the diversity of consumers can impact the stability of their resources. However, the effects of 29 predator diversity on the stability of lower trophic levels (cascading effects of predator diversity) 30have not yet been studied. We conducted a field pond mesocosm experiment and accompanying 31 laboratory microcosm experiment in which we grew phytoplankton with zooplankton herbivores, 32manipulating the presence and co-habitation of two heteropteran predators while controlling for 33 total expected predation. We hypothesized that if the predators partitioned their herbivore prey, 34 for example by size, then co-presence of the predators would lead to 1) increased average values 35and 2) decreased temporal variability of phytoplankton biomass. We present evidence that the 36 predators partitioned their herbivore prey, and found that this simultaneous suppression of 37 different herbivore groups reduced the variability of edible (smaller) phytoplankton biomass, 38 without affecting mean phytoplankton biomass. We also found that phytoplankton more resistant 39 to herbivory were not affected by our manipulations, indicating that the zooplankton herbivores 40 played an important role in mediating this cascading diversity-stability effect. Our results 41 demonstrate that predator diversity can indirectly stabilize primary producer biomass via a 42 "diversity-stability cascade" in the manner of a trophic cascade, seemingly dependent on 43 predator complementarity and the vulnerability of taxa to consumption, and independent of a 44 more traditional trophic cascade in which average biomass is enhanced. Predator diversity, 45 especially in terms of functional traits relating to differential prey use such as body size, may be 46 3 important for regulating ecosystem stability, and may provide a way to improve the reliability of 47 algal crop yields via biological control. 48 49

Beyond the fish-Daphniaparadigm: testing the potential forNeoplea striola(Hemiptera: Pleidae) to cause a trophic cascade in subtropical ponds

“…First, it is possible Neoplea's predation rate was similar enough to the reproduction rate of its prey that prey populations did not significantly change over the course of the 46-day experiment, a scenario most likely if Neoplea preferred prey with short generation times such as cladocerans. While a few studies observed predation by Neoplea on various prey taxa, we are aware of only one study that measured the effect of Neoplea on the biomass of prey taxa over time (Rakowski et al 2019). In that study Neoplea had strong effects on non-copepod zooplankton, which were dominated by fast-reproducing cladocerans, on the short term (under one cladoceran generation).…”

“…Based on previous research (Rakowski et al 2019), we expected Neoplea to have differential effects on zooplankton based on behavior and size. Copepods have faster escape responses than the other zooplankton present, so we analyzed their biomass separately.…”

Synchrony and Stability in Trophic Metacommunities: When Top Predators Navigate in a Heterogeneous World

“…With such a platform, long-term experiments with large fish populations can be performed in a controlled environment, which is close to a natural shallow pond integrating littoral, benthic, and pelagic zones. However, a strong sampling effort is required to get the time series of predator-prey dynamics and assess their temporal stability (Rakowski et al, 2019).…”

Nutrient cycling and self‐regulation determine food web stability

“…Other measures, such as species persistence (the fraction of surviving species after a given time) and temporal variability (the coefficient of variation of biomass), describe the response of each species (Brose et al, 2006;Heckmann et al, 2012;Shanafelt & Loreau, 2018), and provide more insight into stability at different scales (from population to ecosystem, see Haegeman et al, 2016). Moreover, temporal variability is often used in empirical studies (Gross et al, 2014;Rakowski et al, 2019;Tilman et al, 2006); thus, using this measure of stability in mathematical models strengthens the relevance of theoretical results for empirical ecology. Quévreux, Barot, et al (2021), who considered a food web model including up to 50 species and a maximum of four trophic levels, showed with these two measures that nutrient cycling affects food web stability mainly through its enrichment effect.…”