Spatial variability of emergence, splash, surge, and submergence in wave-exposed rocky-shore ecosystems

To distinguish the intertidal states of emergence, splash, surge, and submergence and record their relative durations, we deployed a water-level logger paired with a temperature logger in the mid-intertidal zone at each of 10 wave-exposed sites during the summer in the northeast Pacific. Relative durations of intertidal states were different among the different sites, even at sites close together. Splash was temporally variable, being recorded by the loggers on 50% or fewer days at most sites. Daily surge durations tended to be longer at sites in northern and central California compared with sites in Oregon and Washington. Return times to surge and submergence showed the opposite trend with longer return times in Oregon and Washington compared with California. We estimated the effect of interannual changes in tides on intertidal states by applying the logger data to tidal predictions and comparing duration and return time over the 18.6-yr tidal epoch. Over long time periods, compared with the logger deployments, daily durations of surge increased, return times to the surge state became more uniform, and return times to submergence lengthened.