title: Ocean acidification affects marine chemical communication by changing structure and function of peptide signalling molecules.
abstract: Ocean acidification is a global challenge that faces marine organisms in the near future with a predicted rapid drop in pH of up to 0.4 units by the end of this century. Effects of the change in ocean carbon chemistry and pH on the development, growth and fitness of marine animals are well documented. Recent evidence also suggests that a range of chemically mediated behaviours and interactions in marine fish and invertebrates will be affected. Marine animals use chemical cues, for example, to detect predators, for settlement, homing and reproduction. But, while effects of high CO2conditions on these behaviours are described across many species, little is known about the underlying mechanisms, particularly in invertebrates. Here, we investigate the direct influence of future oceanic pH conditions on the structure and function of three peptide signalling molecules with an interdisciplinary combination of methods. NMR spectroscopy and quantum chemical calculations were used to assess the direct molecular influence of pH on the peptide cues, and we tested the functionality of the cues in different pH conditions using behavioural bioassays with shore crabs (Carcinus maenas) as a model system. We found that peptide signalling cues are susceptible to protonation in future pH conditions, which will alter their overall charge. We also show that structure and electrostatic properties important for receptor binding differ significantly between the peptide forms present today and the protonated signalling peptides likely to be dominating in future oceans. The bioassays suggest an impaired functionality of the signalling peptides at low pH. Physiological changes due to high CO2conditions were found to play a less significant role in influencing the investigated behaviour. From our results, we conclude that the change of charge, structure and consequently function of signalling molecules presents one possible mechanism to explain altered behaviour under future oceanic pH conditions.
authors.affiliation: Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Christina C
authors.identifier: 0000-0002-8566-3078
authors.initials: CC
authors.lastname: Roggatz
authors.affiliation: Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Lorch
authors.affiliation: School of Biological, Biomedical and Environmental Sciences, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Hardege
authors.affiliation: Department of Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, UK.
authors.forename: David M
authors.initials: DM
authors.lastname: Benoit
mesh_terms: D000818:Animals; D003386:Brachyura / Q000502:physiology; D057231:Climate Change; D005399:Fishes / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007448:Invertebrates / Q000502:physiology; D009792:Oceans and Seas; D010455:Peptides / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry*
chemical_list: D010455:Peptides
keywords: 
  Carcinus maenas
  ; 
  DFT
  ; NMR chemical shift calculation; chemically mediated behaviour; chemoreception; info-disruption; molecular effects of pH; molecular electrostatic potential; pKa determination by 1H NMR; peptide conformation