Individual variability in reproductive success determines winners and losers under ocean acidification: a case study with sea urchins

PLoS One. 2012;7(12):e53118. doi: 10.1371/journal.pone.0053118. Epub 2012 Dec 27.


Background: Climate change will lead to intense selection on many organisms, particularly during susceptible early life stages. To date, most studies on the likely biotic effects of climate change have focused on the mean responses of pooled groups of animals. Consequently, the extent to which inter-individual variation mediates different selection responses has not been tested. Investigating this variation is important, since some individuals may be preadapted to future climate scenarios.

Methodology/principal findings: We examined the effect of CO(2)-induced pH changes ("ocean acidification") in sperm swimming behaviour on the fertilization success of the Australasian sea urchin Heliocidaris erythrogramma, focusing on the responses of separate individuals and pairs. Acidification significantly decreased the proportion of motile sperm but had no effect on sperm swimming speed. Subsequent fertilization experiments showed strong inter-individual variation in responses to ocean acidification, ranging from a 44% decrease to a 14% increase in fertilization success. This was partly explained by the significant relationship between decreases in percent sperm motility and fertilization success at ΔpH = 0.3, but not at ΔpH = 0.5.

Conclusions and significance: The effects of ocean acidification on reproductive success varied markedly between individuals. Our results suggest that some individuals will exhibit enhanced fertilization success in acidified oceans, supporting the concept of 'winners' and 'losers' of climate change at an individual level. If these differences are heritable it is likely that ocean acidification will lead to selection against susceptible phenotypes as well as to rapid fixation of alleles that allow reproduction under more acidic conditions. This selection may ameliorate the biotic effects of climate change if taxa have sufficient extant genetic variation upon which selection can act.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Australasia
  • Climate Change*
  • Female
  • Hydrogen-Ion Concentration
  • Male
  • Models, Theoretical
  • Oceans and Seas*
  • Reproduction / physiology*
  • Sea Urchins / physiology*
  • Sperm Motility / physiology

Grant support

This work was funded by the Australian Research Council and a Linnaeus-grant from the Swedish Research Councils VR-Review and Formas (Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning)( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.