Variation in the response of crustacean zooplankton species richness and composition to the invasive predator Bythotrephes longimanus

Abstract

The predacious invertebrate Bythotrephes longimanus has now invaded >90 freshwater lakes in North America. There is some evidence that B. longimanus has a negative effect on summer zooplankton species richness; however, no study has examined the effect of B. longimanus throughout the ice-free season in more than one lake. We visited 10 invaded and 4 reference lakes every 2 weeks from May to September, collecting B. longimanus, crustacean zooplankton, and water chemistry samples. Composite samples were pooled across the study season for each lake. Bythotrephes longimanus significantly reduced cladoceran species richness, diversity, and abundance, and the total zooplankton community also exhibited decreased richness, diversity, and abundance. Seasonal sampling was better than synoptic surveys at detecting changes in abundance, but richness estimates were similar. As B. longimanus continues to spread across lake landscapes, we expect it will have profound impacts on local and regional richness and species distribution patterns.

Direct and indirect effects of an invasive planktonic predator on pelagic food webs

“…Lack of increases in phytoplankton biomass at the whole-lake scale was also observed by Lehman (1988) in Lake Michigan and by Strecker and Arnott (2008) in a subset of our lakes. In experimental mesocosms, increases in chlorophyll (phytoplankton biomass) in the presence of Bythotrephes, consistent with trophic cascades, were observed (Strecker and Arnott 2005). Conversely, Wahlströ m and Westman (1999) observed no significant effect of Bythotrephes on chlorophyll in enclosures.…”

“…1). The compositional effects of environmental variables and Bythotrephes on crustacean zooplankton and rotifer communities have been welldescribed elsewhere (Hovius et al 2006;Strecker et al 2006); please see Fig. 2 for specific relationships between variables and communities.…”

“…Zooplankton species were grouped into size classes (0-0.4, 0.4-0.8, 0.8-1.2, 1.2-1.6, and . 1.6 mm) derived from a concurrent study in a subset of our study lakes (Strecker and Arnott 2008), and they were assigned to functional groups using the classification of Barnett et al (2007) ( Table 2). Rotifers were identified to genus, and phytoplankton were identified to species but grouped at the family level for analyses (i.e., bacillariophyceae, chlorophyceae, chrysophyceae, cryptophyceae, pyrrhophyceae, cyanophyceae).…”

“…The cladoceran zooplankter Bythotrephes longimanus is an invasive predator in North America, where it occupies a mid-trophic-level position in lakes. It has had large effects on pelagic herbivore community structure, biomass, and productivity in North American lakes (Yan et al 2002;Boudreau and Yan 2003;Strecker and Arnott 2008). Based on the strong effects of this invader on herbivorous zooplankton, we would expect to see strong cascading effects on lower trophic levels, including changes in taxonomic composition, size, and structure, and functional group composition in the phytoplankton.…”

Dynamics of the invasive spiny water flea, Bythotrephes longimanus, in Lake Simcoe, Ontario, Canada

“…Bythotrephes is a voracious predator of crustacean zooplankton, capable of altering the trophic structure of lakes (Rennie et al 2011). Its invasion is routinely associated with reductions in the species richness of crustacean zooplankton and cladoceran standing stocks (Yan and Pawson 1997, Dumitru et al 2001, Boudreau and Yan 2003, Barbiero and Tuchman 2004, Strecker et al 2006, alterations in the behaviour of the zooplankton (Pangle et al 2007, Young and Yan 2008, Bourdeau et al 2011, and the displacement of native predatory invertebrates Sprules 2009, Weisz and. Bythotrephes may compete with planktivorous fish for prey (Lehman 1991, Garton et al 1993, Hoffman et al 2001, Foster and Sprules 2010, diverting energy away from higher trophic levels (Dumitru et al 2001, Strecker and Arnott 2008, Foster and Sprules 2010.…”