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

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.