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Acidification can directly affect olfaction in marine organisms

Porteus, Cosima S.; Roggatz, Christina C.; Velez, Zelia; Hardege, Jörg D.; Hubbard, Peter C.


Cosima S. Porteus

Christina C. Roggatz

Zelia Velez

Peter C. Hubbard


In the past decade, many studies have investigated the effects of low pH/high CO2 as a proxy for ocean acidification on olfactory-mediated behaviours of marine organisms. The effects of ocean acidification on the behaviour of fish vary from very large to none at all, and most of the maladaptive behaviours observed have been attributed to changes in acid–base regulation, leading to changes in ion distribution over neural membranes, and consequently affecting the functioning of gamma-aminobutyric acid-mediated (GABAergic) neurotransmission. Here, we highlight a possible additional mechanism by which ocean acidification might directly affect olfaction in marine fish and invertebrates. We propose that a decrease in pH can directly affect the protonation, and thereby, 3D conformation and charge distribution of odorants and/or their receptors in the olfactory organs of aquatic animals. This can sometimes enhance signalling, but most of the time the affinity of odorants for their receptors is reduced in high CO2/low pH; therefore, the activity of olfactory receptor neurons decreases as measured using electrophysiology. The reduced signal reception would translate into reduced activation of the olfactory bulb neurons, which are responsible for processing olfactory information in the brain. Over longer exposures of days to weeks, changes in gene expression in the olfactory receptors and olfactory bulb neurons cause these neurons to become less active, exacerbating the problem. A change in olfactory system functioning leads to inappropriate behavioural responses to odorants. We discuss gaps in the literature and suggest some changes to experimental design in order to improve our understanding of the underlying mechanisms and their effects on the associated behaviours to resolve some current controversy in the field regarding the extent of the effects of ocean acidification on marine fish.


Porteus, C. S., Roggatz, C. C., Velez, Z., Hardege, J. D., & Hubbard, P. C. (2021). Acidification can directly affect olfaction in marine organisms. The journal of experimental biology, 224(14),

Journal Article Type Article
Acceptance Date May 26, 2021
Online Publication Date Jul 28, 2021
Publication Date Jul 1, 2021
Deposit Date Jul 28, 2021
Publicly Available Date Oct 27, 2022
Journal Journal of Experimental Biology
Print ISSN 0022-0949
Electronic ISSN 1477-9145
Publisher The Company of Biologists
Peer Reviewed Peer Reviewed
Volume 224
Issue 14
Keywords Acidification; Behaviour; Carbon dioxide; Electrophysiology; Fish; Invertebrates
Public URL


Published article (830 Kb)

Copyright Statement
© 2021. Published by The Company of Biologists Ltd

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