Resistance of rocky intertidal communities to oceanic climate fluctuations

change rates were weakly associated with mean ENSO index (R2 = -0.003; Fig 10a; Table 4b) and the years since sea star wasting disease (R2 = -0.019; Fig 10b; Table 4b). In the low zone, community change rate increased slightly with increasing maximum daily air temperature (R2 = 0.069; Fig 10c; Table 4c). Table 2. Results of 3 PERMANOVA analyses testing drivers of community dissimilarity in a) high, b) mid, and c) low intertidal zones in Oregon and northern Cali- fornia from 2006–2021. We tested the effects of site (nested within cape) as a random factor and the effects of climate variables for mean Pacific Decadal Oscillation index (mean PDO), mean North Pacific Gyre Oscillation index (mean NPGO), mean El Niño Southern Oscillation index (mean ENSO), mean and standard deviation of the Biologically Effective Upwelling Transport Index (mean and SD BEUTI, respectively), mean daily sea surface temperature (Mean SST), mean daily maximum air tem- perature (Max Air Temp), and years since the sea star wasting disease epidemic (Yr Since SSWD). Communities were analyzed at the quadrat level in the mid and high zones (0.5 x 0.5m) and the transect level in the low zone (the average of ~10 0.5 x 0.5m quadrats). Bold statistics indicate that >10% of variation was explained by a given factor. a) High Zone Source df SS MS Pseudo-F P Estimate Sq.root % Explained Mean PDO 1 7,842 7,842 8.92 0.001 55.0 7.41 3.8 Mean NPGO 1 7,583 7,583 8.62 0.001 55.1 7.42 3.8 Mean ENSO 1 6,526 6,526 7.42 0.001 32.5 5.70 2.2

Mean BEUTI 1 5,020 5,020 5.71 0.001 31.2 5.58 2.2 SD BEUTI 1 1,900 1,900 2.16 0.056 4.6 2.14 0.3 Mean SST 1 3,570 3,570 4.06 0.001 23.2 4.81 1.6 Max Air Temp 1 2,312 2,312 2.63 0.018 8.9 2.98 0.6 Yr Since SSWD 1 3,124 3,124 3.55 0.004 22.1 4.70 1.5 Site 5 121,360 24,272 27.60 0.001 333.6 18.27 23.1 Residual 560 492,460 879 879.4 29.65 60.8 Total 573 742,780 1445.4 b) Mid Zone Source df SS MS Pseudo-F P Estimate Sq.root % Explained Mean PDO 1 12,885 12,885 15.40 0.001 112.0 10.59 6.1 Mean NPGO 1 6,593 6,593 7.88 0.001 157.4 12.54 8.6 Mean ENSO 1 5,797 5,797 6.93 0.001 71.7 8.47 3.9 Mean BEUTI 1 5,090 5,090 6.08 0.001 43.9 6.63 2.4 SD BEUTI 1 6,355 6,355 7.60 0.001 35.1 5.93 1.9 Mean SST 1 2,742 2,742 3.28 0.012 28.6 5.35 1.6 Max Air Temp 1 3,296 3,296 3.94 0.002 16.3 4.04 0.9 Yr Since SSWD 1 8,274 8,274 9.89 0.001 292.2 17.09 15.9 Site 5 84,260 16,852 20.14 0.001 239.4 15.47 13.1 Residual 541 452,660 837 836.7 28.93 45.6 Total 554 663,550 1833.4 c) Low Zone Source df SS MS Pseudo-F P Estimate Sq.root % Explained Mean PDO 1 1,187 1,187 2.03 0.032 7.1 2.66 0.6 Mean NPGO 1 8,489 8,489 14.52 0.001 56.4 7.51 4.5 Mean ENSO 1 4,851 4,851 8.3 0.001 32.9 5.74 2.6 Mean BEUTI 1 3,065 3,065 5.24 0.001 53.2 7.3 4.2 SD BEUTI 1 587 587 1 0.43 0 0.13 0 Mean SST 1 2,579 2,579 4.41 0.001 23 4.79 1.8 Max Air Temp 1 730 730 1.25 0.252 1.5 1.21 0.1

Yr Since SSWD 1 8,977 8,977 15.35 0.001 78.6 8.87 6.2 Site 10 112,240 11,224 19.19 0.001 422.1 20.55 33.5 Residual 317 185,370 585 584.8 24.18 46.4 Total 335 365,900 1259.6 https://doi.org/10.1371/journal.pone.0297697.t002 PLOS ONE Resistance of rocky intertidal communities PLOS ONE | https://doi.org/10.1371/journal.pone.0297697 May 29, 2024 16 / 34