Effects of acidification on olfactory-mediated behaviour in freshwater and marine ecosystems: a synthesis

Abstract

For many aquatic organisms, olfactory-mediated behaviour is essential to the maintenance of numerous fitness-enhancing activities, including foraging, reproduction and predator avoidance. Studies in both freshwater and marine ecosystems have demonstrated significant impacts of anthropogenic acidification on olfactory abilities of fish and macroinvertebrates, leading to impaired behavioural responses, with potentially far-reaching consequences to population dynamics and community structure. Whereas the ecological impacts of impaired olfactory-mediated behaviour may be similar between freshwater and marine ecosystems, the underlying mechanisms are quite distinct. In acidified freshwater, molecular change to chemical cues along with reduced olfaction sensitivity appear to be the primary causes of olfactory-mediated behavioural impairment. By contrast, experiments simulating future ocean acidification suggest that interference of high CO 2 with brain neurotransmitter function is the primary cause for olfactory-mediated behavioural impairment in fish. Different physico-chemical characteristics between marine and freshwater systems are probably responsible for these distinct mechanisms of impairment, which, under globally rising CO 2 levels, may lead to strikingly different consequences to olfaction. While fluctuations in pH may occur in both freshwater and marine ecosystems, marine habitat will remain alkaline despite future ocean acidification caused by globally rising CO 2 levels. In this synthesis, we argue that ecosystem-specific mechanisms affecting olfaction need to be considered for effective management and conservation practices.

Ocean acidification alters the response of intertidal snails to a key sea star predator

“…These combined results suggest that behavioural impairment under OA may be at least somewhat general across taxa [8,12]. The physiological mechanisms underlying OA-induced behavioural shifts in fish appear to revolve around degraded function of ion channels that involve the neurotransmitter gamma-aminobutyric acid (GABA; [7][8][9]), and it may be relevant that GABA receptor molecules are conserved across vertebrates and invertebrates [8].…”

“…Multiple species of fish, for example, fail to properly process waterborne cue information when confronted with the scent of predators [5,6]. Such impaired behaviours appear to originate from altered neurotransmitter and ion channel function under conditions of reduced seawater pH [7][8][9]. Fewer studies have explored the potential for analogous effects in invertebrates, although limited evidence suggests that perturbed neuronal function under OA may arise quite generally [10][11][12][13][14].…”

Paradigm Lost: Ocean Acidification Will Overturn the Concept of Larval-Fish Biophysical Dispersal

“…This has led to conclusions that there is clear "potential for natural variation in sensitivity among individuals to lead to genetic adaptation in marine fishes" (Leduc et al, 2013). However, this is true only if the variation has a genetic basis and is heritable a recent study on A. polyacanthus has found this for temperature (Munday et al, 2017b).…”

Ocean acidification alters fish–jellyfish symbiosis

“…Most fishes associating with jellyfish do not have any immunity against jellyfish toxins [8], and therefore need to continuously adjust their position relative to the pulsating jellyfish host to avoid contact with the cnidocytes on their oral arms or tentacles [15,29]. Ocean acidification can reverse or alter a wide range of animal behaviours mediated by vision, olfaction or audition in fishes as well as invertebrates [18,30] by interfering with the brain neurotransmitter function [31,32]. The potential for acclimation and adaptation in fishes towards ocean acidification effects remains elusive [33,34].…”