Original paper
Large daphniids are keystone species that link fish predation and phytoplankton in trophic cascades
Ogorelec, Žiga; Wunsch, Carsten; Kunzmann, Alessandra Janina; Octorina, Pelita; Navarro, Jana Isanta
Fundamental and Applied Limnology Volume 194 Nr. 4 (2021), p. 297 - 309
67 references
published: Feb 25, 2021
published online: Nov 26, 2020
manuscript accepted: Oct 12, 2020
final revised version received: Oct 12, 2020
manuscript revision requested: Sep 12, 2020
manuscript received: Jun 20, 2020
Open Access (paper may be downloaded free of charge)
Abstract
Daphniids act as keystone species in lake ecosystems by controlling phytoplankton biomass and experiencing intense fish predation. However, the importance of single daphniid species as trophic links between phytoplankton and fish remains unclear, especially compared with other zooplankton taxa. To disentangle the role of individual zooplankton taxa in the food web of a large lake, we performed an in-situ mesocosm experiment with natural phytoplankton and zooplankton communities in three treatments with native, invasive or no fish predators, respectively. A large daphniid, Daphnia longispina, was the zooplankter most strongly predated by both fish species, and also had the highest top-down effects on phytoplankton. All other zooplankton taxa, including a small daphniid species, had minor roles in terms of both predation by fish and grazing on phytoplankton. We suggest that daphniid species with large body sizes can strongly link higher and lower trophic levels in lake food webs, and thus function as keystone species in trophic cascades from fish to phytoplankton.
Keywords
Cladocera • Daphnia • food chain • ecosystem dynamics • oligotrophic lake • pelagic • trophic cascading