Influence of light on the foraging impact of an introduced predatory cladoceran, B ythotrephes longimanus

SummaryIdentifying factors that influence the foraging ability of an introduced predator is essential for assessing its potential impact on the invaded community. We conducted a series of in situ enclosure experiments to determine the effect of light on the foraging ability and community‐level effects of the invasive cladoceran B ythotrephes longimanus in lakes. In 1‐L enclosures with only D aphnia prey, a strong effect of predation under ambient light conditions was observed. There was no evidence of predation in dark treatments, suggesting that B ythotrephes is unable to feed by mechanoreception alone. A subsequent experiment using larger enclosures exposed an assemblage of prey from an uninvaded lake to B ythotrephes predation across a similar light gradient. Consistent with regional lake surveys, B ythotrephes reduced cladoceran abundance under ambient light conditions. At the community level, predation effects were overall strongest under ambient light; however, the influence of light on predation varied across trials that differed in initial community structure of prey. Also, some predation under dark conditions was possible on C eriodaphnia and B osmina , suggesting that D aphnia , in particular, may be less vulnerable under low‐light conditions. Our results suggest that light refuges for some prey taxa could play an important role in mediating the impact of B ythotrephes .