Ocean acidification: impacts on top predators and processes of importance

Chair: Martin Grosell

Karen Evans1, 2, Alistair J. Hobday1, 2, Joel Llopiz3


1 CLIOTOP Scientific Steering Committee, c/o IMBER, Bergen, Norway

2 CSIRO Oceans and Atmosphere, GPO 1538, Hobart, Tasmania 7001, Australia

3 Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543, USA


Marine top predators, such as tunas, sharks, marine mammals and seabirds, are an important component of oceanic environments, providing a range of ecosystem services. The CLimate Impacts On TOp Predators (CLIOTOP) science program, supported by IMBER, is an international network of researchers, managers, and policy makers involved in research related to large marine species. CLIOTOP seeks to develop predictive capability for these socio-ecological systems and evaluate adaptation options to ensure future sustainability. A focus is large-scale comparative efforts to elucidate key processes involved in the interaction between climate variability and change — including ocean acidification (OA) — and human uses of the ocean on the structure of pelagic ecosystems and large marine species.


We review known direct and indirect impacts of OA on oceanic predators and important key processes. We provide an overview of research conducted under the CLIOTOP program and perspectives on research directions.


Studies investigating the direct influence of OA on marine top predators are limited. Studies to date have largely shown no direct relationship between ‘near future’ levels and survivorship at least in fish species, and it is therefore believed for many species that indirect impacts via food chains and potential non-linear interactions pose the greatest risk. Limited evidence for OA impacts on egg fertilisation and development, and larval development have been observed in oceanic tuna species. Modelling initiatives have also highlighted that changes to ocean pCO2 cannot be considered in isolation, particularly given the influence of variability in both temperature and dissolved oxygen on the survival of early life stages and on the ecosystems supporting marine top predators.


Understanding the impacts of OA on top predators is in its infancy. CLIOTOP, via dedicated task teams, aims to progress understanding in this underdeveloped area of research.