Strategies of zooplanktivory shape the dynamics and diversity of littoral plankton communities: a mesocosm approach

Abstract

Planktivorous fish can exert strong top-down control on zooplankton communities. By incorporating different feeding strategies, from selective particulate feeding to cruising filter feeding, fish species target distinct prey. In this study, we investigated the effects of two species with different feeding strategies, the three-spined stickleback (Gasterosteus aculeatus (L.)) and roach (Rutilus rutilus (L.)), on a low-diversity brackish water zooplankton community using a 16-day mesocosm experiment. The experiment was conducted on a small-bodied spring zooplankton community in high-nutrient conditions, as well as a large-bodied summer community in low-nutrient conditions. Effects were highly dependent on the initial zooplankton community structure and hence seasonal variation. In a small-bodied community with high predation pressure and no dispersal or migration, the selective particulate-feeding stickleback depleted the zooplankton community and decreased its diversity more radically than the cruising filter-feeding roach. Cladocerans rather than copepods were efficiently removed by predation, and their removal caused altered patterns in rotifer abundance. In a large-bodied summer community with initial high taxonomic and functional diversity, predation pressure was lower and resource availability was high for omnivorous crustaceans preying on other zooplankton. In this community, predation maintained diversity, regardless of predator species. During both experimental periods, predation influenced the competitive relationship between the dominant calanoid copepods, and altered species composition and size structure of the zooplankton community. Changes also occurred to an extent at the level of nontarget prey, such as microzooplankton and rotifers, emphasizing the importance of subtle predation effects. We discuss our results in the context of the adaptive foraging mechanism and relate them to the natural littoral community.

Trait‐dependency of trophic interactions in zooplankton food webs

“…In contrast with perch, roach are cruising foragers that use continuous and rapid swimming, punctuated by slowdowns (Peterka and Matěna , Helenius et al ). They are able to switch between particulate feeding and gulping, depending on zooplankton body size, abundance and light conditions (Van Den Berg et al , Helenius et al ).…”

“…In contrast with perch, roach are cruising foragers that use continuous and rapid swimming, punctuated by slowdowns (Peterka and Matěna , Helenius et al ). They are able to switch between particulate feeding and gulping, depending on zooplankton body size, abundance and light conditions (Van Den Berg et al , Helenius et al ). Roach foraging efficiency is almost independent of the light intensity (Diehl , Nurminen et al ), indicating that they only optionally rely on visual cues to locate their prey.…”

Top-down control of invertebrates by Ninespine Stickleback in Arctic ponds

“…Fish can shape the structure and composition of aquatic communities through top-down control on their invertebrate prey (Power 1990, Carpenter andKitchell 1993). Despite the clear capacity for fishes to drive top-down effects, isolating the role of individual fish species or trophic levels is difficult given the complexity of aquatic food webs (e.g., Winkelmann et al 2011, Helenius et al 2015. Direct effects of predation may be masked or modified by other members of the food web, confusing specific trophic relationships (Polis 1994, Batzer et al 2000.…”

“…The presence of fish may change the composition, richness, abundance, biomass, or size of taxa in the invertebrate community relative to fishless systems (e.g., Gilinsky 1984, Knapp et al 2001, Parker et al 2001, Hornung and Foote 2006, Winkelmann et al 2011. Consumption of a nonrandom subset of prey taxa by newly introduced fish can change richness or composition of invertebrate taxa (Gilinsky 1984, Winkelmann et al 2011, Helenius et al 2015. Often, within gape limitations, fish predators preferentially consume largebodied individuals or taxa, leading to a decrease in the overall size of invertebrates or to a community composed of smaller-bodied species (Brooks and Dodson 1965, Carlisle and Hawkins 1998, Knapp et al 2001.…”

“…Considering the rapid metabolism and dietary flexibility of Ninespine Stickleback (Cameron et al 1973) and the associated high demand for food resources, they are likely to affect their invertebrate prey. In experiments on related species, total invertebrate abundance increased in the presence of Threespine Stickleback Gasterosteus aculeatus because predation pressure on large crustaceans released small-bodied microzooplankton from predation or competition and caused their numbers to rise (Helenius et al 2015). Brook Stickleback Culaea inconstans competed with large-bodied predatory invertebrates for food, which led to depletions of predatory and noninsectivorous invertebrate biomass and functional replacement of invertebrate predators by Brook Stickleback (Hornung and Foote 2006).…”