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Research reveals ocean acidification disrupts marine life communication

Increasing acidification of the world’s oceans has the potential to significantly disrupt the way marine life communicates, with yet unknown consequences for the ecosystem, research by the University of Hull shows.

Increasing levels of CO2 pumped into the atmosphere are altering chemical communication which marine life relies upon to find food, avoid predators and to mate.

The research, published in the Globe Change Biology Journal, is expected to have a big impact as its potential implications range from aquaculture to ecosystem management and conservation.

Ocean acidification occurs when the CO2 in the atmosphere is absorbed by sea water.

Lead author Christina C. Roggatz, a University of Hull PhD student, has shown how ‘smell’ molecules used for communication are significantly affected by this ongoing acidification of the ocean.

Chemical communication using smell molecules is essential for marine organisms. Its importance is comparable to the combined status of vision and hearing in humans.

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What this study shows is that peptide signalling molecules used by marine invertebrates for egg ventilation and hatching of the larvae are altered by acidification of the oceans. Similar signalling cues are involved in mating, finding food or settlement of a wide range of marine animals and are likely to be affected too.

Christina C. Roggatz, University of Hull PhD student

“Imagine you are a little crab, living on a shore with large rocks, deep pools and battled by tides and waves. The only way to find your lunchtime snack would be to smell it from a distance. But the same applies to the octopus on the hunt for you. So you as the little crab rely on smelling the octopus first to avoid being eaten.”

If this was no longer possible it has the potential to significantly affect animal behaviour and interactions. This would add to the well-known effects of ocean acidification on fitness, physiology and reproduction of marine organisms. 

Christina carried out chemical structural analyses of the peptide cues at different pH conditions and used the results for quantum chemical calculations to obtain information about the charge and conformation of the molecules at these conditions. Her analysis revealed significant differences between the molecules present in today’s oceans and those molecules likely to dominate in future pH conditions, which she also visualised using computer simulations. 

She confirmed the chemical and computational results with experiments using shore crabs. The crabs were put into conditions where the water was of normal pH. The crabs were responsive after the smell substance was added. However, when mimicking lower pH conditions in the ocean expected by 2100, the crabs no longer responded to the smell molecules, suggesting if ocean acidification continues, these smell molecules will lose their function, having potentially huge ramifications for the ecosystem.

Christina said: “If all smell molecules in the oceans would be affected in a similar way, the chemical communication in the ocean would be completely disrupted. It would be comparable to a world without light or sound for us humans. 

“Luckily there are many different chemicals involved in chemical communication and a complete “black-out” is unlikely. However, only few signalling molecules are actually known in marine organisms and peptides are a very important class, so the implications of this research could be big.” Christina has been working on the paper throughout her PhD, along with supervisors Professor Mark Lorch, Chemistry, Dr David Benoit, Senior Lecturer in Physical Chemistry and Dr Jörg Hardege, Reader in Chemical Ecology.

Called ‘Ocean acidification affects marine chemical communication by changing structure and function of peptide signalling molecules,’ it is also the first research of its kind to use a cross discipline combination of research methods, including quantum chemical calculations and chemical and biological techniques.

Christina said: “The combination of computational, chemical and biological techniques has helped to reveal the molecular effects and functional consequences on smell molecules as the pH in the ocean changes. This is a completely new and additional mechanism of how ocean acidification can affect marine life.”

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