Kelp Associated Changes in Seawater Chemistry Connect to Transgenerational Effects in the Purple Urchin, Strongylocentrotus purpuratus

Kelp forests can change retention time of seawater, altering water chemistry such as pH and dissolved oxygen (DO), as well as the magnitude and predictability of variability. Such variability across space and time could create the grist for transgenerational plasticity (TGP), where parental experience modifies the phenotype of offspring without affecting the genotype, potentially conferring tolerance to future environmental stress. We sought to characterize this environmental variability and investigate whether it influences the transgenerational physiological response of a key species, the purple urchin, Strongylocentrotus purpuratus. Temperature, pH, and DO were monitored with long term sensor deployments inside and outside a kelp forest at Arroyo Quemado, a Santa Barbara Coastal Long Term Ecological Research site, and time series analysis was conducted to relate water chemistry to kelp biomass. Paired with the sensor deployments, adult S. purpuratus were conditioned inside and outside the kelp for 6 months spanning gametogenesis. Adults from the two acclimation habitats were spawned and the larvae were raised under different pCO₂ conditions in the lab to assess the physiological, transcriptional, and epigenetic response of larvae to the maternal and developmental environments. Larval body size and skeletal growth decreased under high pCO₂ conditions. Thermal tolerance differed by maternal and larval treatment: larvae raised under high pCO₂ were more susceptible to lethal thermal stress; however, within each larval treatment, progeny from outside conditioned mothers had higher thermal tolerance. Offspring of outside conditioned mothers also had lower respiration rates under high pCO_2, while respiration rates between maternal treatments did not differ under low pCO₂. Differences in maternal provisioning will be assessed using egg lipid content. Currently, we are investigating whether there is evidence of TGP at the transcriptomic level, in progeny from urchins inside and outside the kelp forest.