Background/Question/Methods
Recovery of endangered white abalone (Haliotis sorenseni) depends on understanding the effects of climate change on this economically, ecologically, and culturally important species. Ocean acidification (OA), the global decrease of ocean pH due to the absorption of anthropogenic CO2, is known to affect shellfish populations throughout the world; however, the effect of this change on white abalone growth and development is unclear. Endemic to subtidal habitats of southern California, USA and northern Baja California, MEX, overharvesting of white abalone led to the listing of the species as critically endangered under the US Endangered Species Act. In the early 2000’s, the White Abalone Restoration Consortium formed to expand scientific knowledge of white abalone and spearhead restoration efforts. A successful captive breeding program led by UC Davis Bodega Marine Laboratory resulted in approximately 30,000 captive-bred animals for research and stocking. A major effort is now underway to identify optimal wild re-stocking strategies, including studies to understand how white abalone populations will be affected by OA.
Results/Conclusions
To test the potential sensitivity of white abalone to changes in ocean chemistry, which naturally varies regionally along the California coast, we reared white abalone from embryos to post settlement juveniles under both contemporary pH values (8.1 pH, 400 μatm CO2) and acidic conditions that are experienced now during regional upwelling (7.6 pH, 1200 μatm CO2). In addition to pH manipulation, white abalone were settled on two different diets, wild crustose coralline algae (CCA) and surfaces coated with commercially produced diatoms (Navicula sp.). White abalone settled in CCA environments had 28.6% higher post-settlement survival compared to abalone settled on diatoms, and showed a 53% increase in survival if raised on CCA under high CO2 as compared to diatoms. Ongoing results from these experiments will inform the adaptive management of this species in the face of changing ocean chemistry, as well as help inform best practices for the recovery of white abalone and the commercial aquaculture of closely related abalone species, such as the red abalone (Haliotis rufescens).