Beyond calcification: ocean acidification alters invertebrate behaviour via neural impairment

Chair: Martin Grosell

Sue-Ann Watson (1)*, Sjannie Lefevre (2), Mark I. McCormick (1), Paolo Domenici (3), Göran E. Nilsson (2) and Philip L. Munday (1)

1 Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811, Australia
2 Programme for Physiology and Neurobiology, Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway
3 Consiglio Nazionale delle Ricerche – Istituto per l’Ambiente Marino Costiero, Torregrande, 09072 Oristano, Italy

Background
Ocean acidification poses a range of threats to marine invertebrates including reduced growth and calcification. However, the potential effects of rising carbon dioxide (CO2) on marine invertebrate behaviour are largely unknown.

Methods
Marine conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. We habituated humpbacked conch snails to control (405 µatm) and elevated (961 µatm) seawater CO2 at Lizard Island Research Station on the Great Barrier Reef and examined predator-escape behaviours.

Findings
We show that projected future CO2 levels impair mollusc escape behaviours during predator-prey interactions. Elevated-CO2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO2 indicating instead that decision making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA receptor antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO2 in invertebrates, as previously observed in marine fishes.

Conclusions
Altered invertebrate and fish behaviour at projected future CO2 levels could disrupt species interactions, community structure and food web stability with potentially far-reaching implications for marine ecosystems.