Resistance of rocky intertidal communities to oceanic climate fluctuations

(ODFW 19272, 21042, 21848) and the California Department of Fish and Wildlife (SC-4055, S-182930001-18295-001). With exceptions noted below, we surveyed communities separately in each of 3 intertidal zones, with the low zone defined as below mussel beds, the mid zone as mussel beds, and the high zone as above mussel beds. Because of time constraints or lack of habitat, we performed only low zone surveys but not mid or high surveys at Tokatee Klootch- man, Cape Blanco South, Port Orford Heads and both Cape Mendocino sites. In addition, we began most mid and high zone surveys in 2011, five years after the low zone surveys. Because the low zone is patchier and more diverse than the mid and high zones, we used three 30 m transect line(s) parallel to the shore in the low zone at least 20 m apart versus one 30 m transect line in mid and high zones. On each transect, we uniformly (every three meters along transect tapes in mid and high zones) or haphazardly (quadrat tosses in the low zone, avoiding sand, tide pools and large crevices) sampled 10 0.25m2 quadrats (total of 4,588 quadrats). Because we sampled the low zone more thoroughly than the mid and high zones, this may affect met- rics like biodiversity and community structure at the site level, so we analyzed zones separately in all except one model in this study (See Data Analyses). We performed surveys in the same general area each year, but the quadrat locations varied between years. In each gridded quad- rat, we visually estimated the percent cover to the nearest 1% of all visible species, including

sessile algae, sessile invertebrates and bare space and counted total numbers of all mobile Fig 1. Map of sites in Oregon and northern California. Capes included Cape Foulweather in greens (Boiler Bay and Fogarty Creek sites), Cape Perpetua in reds (Yachats Beach, Strawberry Hill and Tokatee Klootchman sites), Cape Blanco in blues (Cape Blanco North, Cape Blanco South, Port Orford Heads and Rocky Point sites), and Cape Mendocino in purples (Cape Mendocino North and South sites). See S1 Table in S1 Appendix for coordinates. https://doi.org/10.1371/journal.pone.0297697.g001 PLOS ONE Resistance of rocky intertidal communities PLOS ONE | https://doi.org/10.1371/journal.pone.0297697 May 29, 2024 5 / 34