Ocean pH time series and drivers of variability along the northern Channel Islands, California, USA
Eastern boundary current systems (EBCSs) experience dynamic fluctuations in seawater pH due to coastal upwelling and primary production. The lack of high resolution pH observations in EBCSs limits the ability to relate field pH exposures to performance of coastal marine species under future ocean change (acidification, warming) This 3 yr study describes spatio temporal pH variability across the northern Channel Islands, along a persistent temperature gradient (1 4degC) within the eastern boundary California Current System. pH and Conductivity, Temperature, Depth, and Oxygen sensors were deployed on island piers in eelgrass and kelp habitat and on a subtidal mooring. Due to event scale primary production, the temperature gradient across the islands did not manifest in a pH gradient. We resolved spatial pH variability on diel (DpHT 0.05 0.2: photosynthesis) event scale (DpHT 7.9. The lowest pH observations >1 SD below mean pHT) occurred under either warm (respiration during warm nights) or cold (advection of upwelled water) temperatures. We emphasize the importance of incorporating site specific environmental variability in studies of ocean change biology, particularly in the design of multistressor experiments.