Transgenerational Plasticity to Elevated CO2 is Maladaptive in the Presence of Multiple Stressors in the Oyster, Saccostrea glomerata

Chair: Philip Boyd

Laura M. Parker (1), Pauline M. Ross (2), Wayne A. O’Connor (3), Maria Byrne (1), Patti Virtue (4), Michael Dove (3), Mitchell Gibbs (2), Elliot Scanes (2), Ross Coleman (
1)

1 Schools of Medical and Biological Sciences, Centre for the Ecological Impacts for Coastal Cities, The University of Sydney, Sydney, NSW, 2006, Australia
2 School of Science and Health, Western Sydney University, NSW, 1797, Australia
3 Port Stephens Fisheries Institute, Department of Primary Industries, Taylors Beach, NSW, 2316, Australia
4 Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, TAS, 7001, Australia.

Background
Understanding whether marine organisms have the capacity to acclimate or adapt to ocean acidification is an area of great uncertainty. Recent transgenerational studies show that for molluscs and other marine organisms, exposure of adults to elevated CO 2 can facilitate the transfer of positive carryover effects to their offspring that help them to survive in future conditions, but it is not known if these positive carryover effects will be beneficial to offspring in the presence of multiple stressors.

Methods
We exposed adults of the oyster, Saccostrea glomerata, to elevated CO2 during reproductive conditioning and examined the impacts of elevated CO2 (control = 395; 856 µatm) combined with elevated temperature (control = 24; 28 ˚C), reduced salinity (control = 35; 25 ppt) and reduced food concentration (control = full; half diet) on their larvae.

Findings
Adult exposure to elevated CO 2 had a positive impact on larvae reared at elevated CO2 as a sole stressor. Larvae from CO2-exposed parents were 8% larger, developed faster and had similar survival at elevated CO2 compared with larvae from ambient-CO2 parents. However, when larvae were reared at elevated CO2 combined with elevated temperature and reduced food concentration (but not reduced salinity), adult exposure to elevated CO2 negatively impacted larval survival. Larvae from CO2-exposed parents suffered a significantly greater reduction in survival, with no survival of larvae in some treatment combinations. Measurement of standard metabolic rate (SMR) showed that across nearly all treatment combinations, larvae from CO2-exposed parents had a significantly higher SMR.

Conclusions
Oyster larvae face an uncertain future in a high CO2 ocean, in the presence of many stressors that they will also encounter. Our results provide the first evidence that transgenerational plasticity to elevated CO2 may be maladaptive in the presence of multiple environmental stressors as larval energy budgets are exceeded.