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

Abstract

Trophic cascadesindirect effects of predators that propagate down through food webshave been extensively documented in many ecosystem types. It has also been shown that predator diversity can mediate these trophic cascades and, separately, that herbivore biomass can influence the stability of primary producers. However, whether predator diversity can cause cascading effects on the stability of lower trophic levels has not yet been studied. We conducted a laboratory microcosm experiment and a field mesocosm experiment manipulating the presence and coexistence of two heteropteran predators and measuring their effects on zooplankton herbivores and phytoplankton basal resources. We predicted that if the predators partitioned their zooplankton prey, for example by size, then the co-presence of the predators would reduce zooplankton prey mass and lead to (1) increased biomass of, and (2) decreased temporal variability of phytoplankton basal resources. We present evidence that the predators partitioned their zooplankton prey, leading to a synergistic suppression of zooplankton. In turn, this enhanced zooplankton suppression led to only a weak, non-significant increase in the central tendency of phytoplankton biomass, but significantly reduced its variability. Our results demonstrate that predator diversity may indirectly stabilize basal resource biomass via a "diversity-stability trophic cascade," seemingly dependent on predator complementarity, even when there is no significant classic trophic cascade altering the central tendency of biomass. Therefore predator diversity, especially if correlated with diversity of prey use, could play a role in regulating ecosystem stability. This link between predator diversity and producer stability has implications for conservation and for potential biological control methods to improve crop yield reliability.

Beyond the fish-Daphnia paradigm: testing the potential for pygmy backswimmers (Neoplea striola) to cause trophic cascades in subtropical ponds

“…Based on previous research, we expected Neoplea to have differential effects on zooplankton based on behavior and size ( Rakowski et al, 2021 ). Copepods have faster escape responses than the other zooplankton present, so we analyzed their biomass separately.…”

Effects of protection and temperature variation on temporal stability in a marine reserve network

“…Alternatively, interspecific competition for scarce resources (e.g., space) can increase with diversity (Menge & Sutherland, 1987), particularly in temperate marine systems composed of generalist species (Pellissier, 2015). However, there is little information about the relative influence of interactions between predators and prey and interactions among competitors on community stability in natural systems (Ives et al., 2005; Rakowski et al., 2021) because it is difficult to extend investigations past one trophic level of competing taxa (Loreau et al., 2021). When asynchrony and stability have been assessed in multitrophic communities, systems may be more stable when the multitrophic linkages rather than just the competitive linkages are considered (Downing et al., 2014; Firkowski et al., 2022; Xu et al., 2021).…”

Will a large complex system be productive?

“…number of trophic levels) diversity (Albert et al, 2022;Buzhdygan et al, 2020;Duffy et al, 2007;Soliveres et al, 2016;Thébault & Loreau, 2003;Wang & Brose, 2018). While these studies reported generally positive biodiversity-ecosystem productivity relationships, their strengths vary considerably across trophic levels and ecosystems (Cardinale et al, 2006;Gruner et al, 2008;Katano et al, 2015;Maureaud et al, 2020;Rakowski et al, 2021;Schneider et al, 2016). One possible explanation for the variable biodiversityproductivity relationships in food webs is the structural complexity of multitrophic systems, as the topology and strengths of trophic interactions act together with species diversity in regulating ecosystem productivity (Ives et al, 2005;Maureaud et al, 2020;Thébault & Loreau, 2003;Wang et al, 2019;Wu et al, 2023).…”

“…Accumulating evidence has indicated that food web connectance and interaction strength play important roles in regulating ecosystem primary productivity (Finke & Denno, 2005;Poisot et al, 2013;Thébault & Loreau, 2003;Wang et al, 2019). One key mechanism underlying the biodiversity effect on primary productivity in food webs is trophic complementarity, which characterizes niche differentiations between species in both resource use and natural enemies (Albert et al, 2022;Poisot et al, 2013;Rakowski et al, 2021). The effect of trophic complementarity was predicted to decrease with increasing connectance between trophic levels (Poisot et al, 2013); therefore, ecosystem productivity may be lower in more connected communities.…”