Salinisation and warming disrupt predator-induced drift behaviour in aquatic predator-prey interactions

Predators act as a major selective force impacting biological communities in riverine ecosystems. Often predation risk is mediated by chemical cues upon which prey species display distinct morphological or behavioural defences. For stream invertebrates, predator-induced behaviours can be drifting and hiding. However, anthropogenic stressors increasingly impact freshwater ecosystems, with predicted consequences on the chemical information transfer, potentially affecting anti-predator behaviour. Despite this, knowledge and research on the extent to which these stressors may affect evolved predator-induced behaviour and subsequent ecosystems is scarce. Therefore, we conducted an outdoor mesocosm experiment (ExStream system) at a lowland stream in Germany, in which we investigated the effects of direct and indirect fish predation on invertebrate communities under different stressor conditions. As stressors, we tested elevated salinity (ambient vs + 136 mg/L NaCl), elevated temperature (ambient vs. + 3.4{degrees}C), and the combination of both. Our findings reveal distinct predator-induced drift behaviour, characterised by a greater number of drifting invertebrates and a concurrent reduction in overall invertebrate numbers in the communities. Increased salinity and temperature hampered the predator-induced drift behaviour. Our results support the possibility that stressors negatively impact the preys ability to perceive predators presence and respond appropriately. This disruption may alter predator-prey relationships, thereby affecting communities and potentially ecosystem functions. Highlights[vrecto] We hypothesised that anthropogenic stressors disrupt predator-induced behaviours in invertebrate prey species. [vrecto]Predator-induced drift behaviour was experimentally studied under ambient and elevated salinity and temperature conditions. [vrecto]Fish exposure elicited predator-induced drift behaviour, which decreased the number of invertebrate individuals of the communities. [vrecto]Elevated salt and elevated temperatures alone and in combination did not induce drift behaviour. [vrecto]We found that both stressors disrupted predator-induced drift behaviour, altering the anti-predator response of invertebrate prey. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/601583v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1eef03borg.highwire.dtl.DTLVardef@1ddda7corg.highwire.dtl.DTLVardef@332bdaorg.highwire.dtl.DTLVardef@1842dbb_HPS_FORMAT_FIGEXP M_FIG C_FIG