Environmental nitrate impacts foraging and agonistic behaviours of invasive non-native crayfish (Pacifastacus leniusculus and Faxonius virilis)

Abstract

Life history traits such as predation and foraging are key behavioural mechanisms through which invasive, non-native species can have a detrimental effect on the resident flora and fauna of recipient ecosystems. Environmental change may alter these traits in ways that are currently poorly understood. In aquatic ecosystems, changes to the environment such as nitrate pollution can have chronic, unforeseen consequences for both native and invasive species. As keystone species and ecosystem engineers, non-native crayfish species can be highly destructive through predating on native species from multiple trophic levels. Here, we assessed the effect of nitrate concentration on the foraging behaviour of two invasive crayfish species from the UK (Pacifastacus leniusculus and Orconectes virilis), particularly focussing on whether there were any species-specific effects of nitrate. During experimental trials, elevated nitrate concentration had a similar impact on the foraging efficacy of both P. leniusculus and O. virilis, slowing both their initial reaction and latency to feed. Nitrate also reduced the ability of both crayfish species to catch live prey as well as the total number of prey consumed. Though both species were similarly influenced by nitrate, we highlight that even at levels deemed safe for drinking water (50 mg NO3 -/L), nitrate concentration can significantly impact the behavioural traits of aquatic species. In the case of invasive species, fluctuations in environmental nitrate concentration could therefore have implications for invader success and impacts on the wider ecosystem.

Aquatic invasive species: introduction to the Special Issue and dynamics of public interest

“…Verdcourt); however, these effects were complex and confounded by depth and frequency of water level fluctuations (Zhang et al, 2021). Another study showed that increased nitrate concentrations decreased agonistic interactions between two invasive crayfish species and reduced their foraging efficiency, which is likely to have complex effects on invasion dynamics (James et al, 2021). Harmful algal blooms (HABs), increasing in frequency with eutrophication, can also shift the balance between invasive and native species as well as between the different invasive species, depending on their tolerance.…”