Effects of Bythotrephes longimanus (Crustacea, Cladocera) on the abundance, morphology, and prey community of Leptodora kindtii (Crustacea, Cladocera)

Abstract

We hypothesized that native Leptodora kindtii would be shorter and have smaller feeding baskets in central Ontario lakes with greater abundances of small-bodied zooplankton prey, and that differences in zooplankton size among lakes could be attributed to the invasive cladoceran Bythotrephes longimanus. We evaluated these conjectures by comparing size metrics of Leptodora and the size of their preferred cladoceran prey in lakes invaded or not by Bythotrephes. Leptodora was less abundant in invaded lakes, but were smaller bodied with smaller feeding baskets only in lakes with long invasion histories. Small cladoceran abundance was greater in noninvaded lakes and was directly related to Leptodora abundance although not to Leptodora size. Mean Leptodora body size declined with increasing abundance of Bythotrephes. We evaluated three possible explanations for these patterns in Leptodora-(a) competition with Bythotrephes for zooplankton prey, (b) direct predation by Bythotrephes, and (c) sizeselective predation by fish. While we were unable to unequivocally distinguish among these hypotheses, our observations are most consistent with predation by Bythotrephes changing zooplankton community composition and size structure in a manner that is detrimental to Leptodora. Our results indicate that Bythotrephes invasion may trigger more complex and subtle changes in food webs than previously thought.

Climate warming restructures an aquatic food web over 28 years

“…Rapid developmental times can also establish a large sediment egg bank that provides a constant source of recruitment if thermal conditions change and become less favourable (Walsh et al., 2016). These differences, along with resulting changes in prey community composition and size structure, have contributed to the replacement of Leptodora in lakes invaded by Bythotrephes (Foster et al., 2012; Kerfoot et al., 2016; Lehman & Cáceres, 1993; Weisz & Yan, 2011). Our findings around phenology also add new insights into this process and raise the risk that introduced Bythotrephes might outcompete native predators under a warming climate in relatively cool lakes like Maggiore.…”

Leptodora kindtii Population Dynamics in the Island Region of Western Lake Erie before and after the Invasion of the Predacious Cladoceran Bythotrephes longimanus

“…Previous studies suggest that B. longimanus invasion caused declines in L. kindtii abdundance in North America Sprules 2009, Weisz and, as well as a trend for smaller L. kindtii size with increased abundances of invasive B. longimanus (Foster et al 2012). Foster et al (2012) suggest size declines in L kindtii in central Ontario lakes invaded by B. longimanus could be due to direct consumption by B. longimanus, indirect effects of B. longimanus decreasing available zooplankton prey for L. kindtii, and other factors, such as fish predation. They concluded that decreased L. kindtii size was due to competitive effects of B. longimanus predation on small cladocerans.…”