Toward a Mechanistic Understanding of Marine Invertebrate Behavior at Elevated CO2

Sue-Ann Watson,Philip L Munday,Jodi T Thomas

doi:10.3389/fmars.2020.00345

Sue-Ann Watson, Philip L Munday + Show 1 more

Open Access

https://doi.org/10.3389/fmars.2020.00345

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Abstract

Elevated carbon dioxide (CO2) levels can alter ecologically important behaviours in a range of marine invertebrate taxa; however, a clear mechanistic understanding of these behavioural changes is lacking. The majority of mechanistic research on the behavioural effects of elevated CO2 has been done in fish, focusing on disrupted functioning of the GABAA receptor (a ligand-gated ion channel, LGIC). Yet, elevated CO2 could induce behavioural alterations through a range of mechanisms that disturb different components of the neurobiological pathway that produces behaviour, including disrupted sensation, altered behavioural choices and disturbed ligand-gated ion channel-mediated neurotransmission. Here, we review the potential mechanisms by which elevated CO2 may affect marine invertebrate behaviours. Marine invertebrate acid-base physiology and pharmacology is discussed in relation to altered GABAA receptor functioning. Alternative mechanisms for behavioural change at elevated CO2 are considered and important topics for future research have been identified. A mechanistic understanding will be important to determine why there is variability in elevated CO2-induced behavioural alterations across marine invertebrate taxa, why some, but not other, behaviours are affected within a species and to identify which marine invertebrates will be most vulnerable to rising CO2 levels.

Highlights

Human activity is resulting in unprecedented amounts of carbon dioxide (CO2) being released into the atmosphere
We demonstrate that the effects of altered GABAA receptor function are likely to be widespread, including non-behavioral effects
We identify other neurobiological mechanisms that should be affected if the GABA hypothesis is correct, propose alternative neurobiological mechanisms by which behavior could be altered by elevated CO2 and suggest techniques to be utilized for future study of elevated CO2-induced behavioral alterations

Summary

Introduction

Human activity is resulting in unprecedented amounts of carbon dioxide (CO2) being released into the atmosphere. Mechanistic support for the GABA hypothesis in marine invertebrates comes from recent studies indicating changes in ion concentration and altered behavior in the same species at elevated CO2 (Table 1). Asian shore crab larvae had altered chemical cue-induced photosensitive behavior and increased extracellular osmolality, but similar extracellular [Cl−] at elevated CO2 (1,380 μatm pCO2) compared to controls (461 μatm pCO2) (Charpentier and Cohen, 2016).

Results

Conclusion