Coupling Eco-Physiology and Shell Geochemistry of California Mussels: Carry-Over Effects of Larval Exposure to Upwelling and Relaxation Regimes

Laboratory studies have shown that environmental conditions experienced by marine invertebrate larvae can create long-lasting effects that shape the performance of juvenile and adult stages. In a naturally variable marine environment, establishing the link between the in situ environmental exposure of an animal and its physiological performance will enhance our predictions of the biological consequences of long-term anthropogenic change. However, in study systems such as zooplankton communities, it is often difficult to reconstruct the environmental conditions to which study organisms have been exposed. Here, we tested how differing histories of environmental exposure during the larval phase shape the subsequent performance of benthic Mytilus californianus mussel recruits. In particular, we reconstructed the in situ pH conditions experienced by mussels during planktonic dispersal by analyzing remnants of their larval shells for the composition of U/Ca, a recently developed biogeochemical proxy. Six cohorts of mussel recruits, each obtained from a two-week deployment of collectors in the intertidal zone at Bodega Marine Reserve, CA, were analyzed to assess rates of oxygen consumption, condition index, growth rate, and shell thickness. Metabolic rate was higher for recruits that arrived during periods of upwelling vs. those that arrived during conditions of relaxation or non-upwelling. However, other metrics of performance did not differ among these groups. We also correlated individual performance with pH exposure of the larval stage estimated from shell U/Ca. Future ocean acidification may intensify these biological responses to underlying variability in coastal ocean chemistry.