Indirect food web effects of Bythotrephes invasion: responses by the rotifer Conochilus in Harp Lake, Canada
- 126 Downloads
As a recent invader of North American lakes, Bythotrephes longimanus has induced large changes in crustacean zooplankton communities through direct predation effects. Here we demonstrate that Bythotrephes can also have indirect food web effects, specifically on rotifer fauna. In historical time series data, the densities of the colonial rotifer Conochilus unicornis significantly increased after Bythotrephes invasion in Harp Lake, Ontario. No such changes were observed in a non-invaded reference lake, the nearby Red Chalk Lake. Evidence for two mechanisms explaining the Conochilus increase was examined based on changes to the crustacean zooplankton community over time. Rapid and severe declines in several herbivorous species of cladoceran zooplankton after Bythotrephes detection indicated a decrease in exploitative competition pressure on Conochilus. Secondly, a later and significant decline to virtual extinction of native invertebrate predators (Mesocyclops and Leptodora) could account for the observed Conochilus increase which also began 1–2 years after invasion by Bythotrephes. Ultimately, it appears that both reduced competition followed by a loss of native invertebrate predators were necessary to lead to the large Conochilus densities observed following invader establishment. From this analysis of long-term community data, it appears that Bythotrephes has important indirect, as well as direct, food web effects in newly invaded North American lakes with implications for trophic relationships.
KeywordsBythotrephes Conochilus Harp Lake Rotifers Competition Predation Zooplankton Indirect effects
Unable to display preview. Download preview PDF.
Thanks to the Ontario Ministry of the Environment, Dorset, Ontario, Canada, for providing samples collected between 1986 and 1998 to be counted for rotifer densities and for providing chemistry and zooplankton densities. Funding was provided by a Department of Fisheries and Oceans subvention grant to BEB and by NSERC grants to BEB, KSM and NDY.
- Arndt H (1993) Rotifers as predators on components of the microbial web (bacteria heterotrophic flagellates, ciliates)—a review. Hydrobiologia 255/256:231–246Google Scholar
- Branstrator DK (1995) Ecological interactions between Bythotrephes cederstroemi and Leptodora kindtii and the implications for species replacement in Lake Michigan. J Great Lakes Res 21:670–679Google Scholar
- Branstrator DK, Lehman JT (1991) Invertebrate predation in Lake Michigan: regulation of Bosmina longirostris by Leptodora kindtii. Limnol Oceanogr 36:483–495Google Scholar
- Brett MT, Goldman CR (1994) Differential effects of zooplankton species on ciliate community structure. Limnol Oceanogr 39:486–492Google Scholar
- Dillon PJ, Molot LA (2005) Long-term trends in catchment export and lake retention of dissolved organic carbon, dissolved organic nitrogen, total iron and total phosphorus: the Dorset, Ontario study, 1978–1998. J␣Geophys Res. doi: 10.1029/2004JG000003.Google Scholar
- Gilbert JJ (1989) The effect of Daphnia interference on a natural rotifer and ciliate community: short-term bottle experiments. Limnol Oceanogr 34:606–617Google Scholar
- Lunte CC, Luecke C (1990) Trophic interactions of Leptodora in Lake Michigan. Limnol Oceanogr 35:1091–1100Google Scholar
- Sprules GS, Riessen HP, Jin EH (1990) Dynamics of the Bythotrephes invasions of the St. Lawrence Great Lakes. J Great Lakes Res 16:346–351Google Scholar
- Vanderploeg HA, Liebig JR, Omair M (1993) Bythotrephes predation on Great Lakes’ zooplankton measured by an in situ method: implications for zooplankton community structure. Archiv fur Hydrobiologie 127:1–8Google Scholar
- Walz N (1995) Rotifer populations in plankton communities: Energetics and life history strategies. Experientia 51:437–453Google Scholar