Resistance of rocky intertidal communities to oceanic climate fluctuations

Table 1. Results of a) a PERMANOVA analysis testing the effects of zones, capes, sites, years, and their interactions on intertidal community dissimilarity in Oregon and Northern California from 2006–2021. Cape, site, and year were treated as random factors. b) Results of SIMPER analysis testing the contributions of taxa to within-zone similarity. Only the top ten taxa contributing most strongly to within-zone similarity are listed. Communities were analyzed at the transect level (the average of ~10 0.5 x 0.5m quadrats). a) PERMANOVA for Zone, Cape, Site, and Year Source df SS MS Pseudo-F P Estimate Sq.root % Explained Zone 2 281,830 140,920 18.43 0.001 1698.00 41.21 55.3 Cape 3 88,568 29,523 3.01 0.001 187.65 13.70 6.1 Year 14 53,610 3,829 4.10 0.001 97.61 9.88 3.2 Site[Cape] 7 53,955 7,708 11.77 0.001 190.69 13.81 6.2 Zone*Cape 4 24,899 6,225 2.28 0.001 146.05 12.09 4.8 Zone*Year 20 22,113 1,106 2.76 0.001 100.37 10.02 3.3 Cape*Year 38 31,580 831 1.26 0.008 23.00 4.80 0.7 Zone*Site[Cape] 6 14,146 2,358 6.31 0.001 164.28 12.82 5.3 Site[Cape]*Year 76 48,494 638 1.43 0.001 61.88 7.87 2.0 Zone*Cape*Year 35 13,968 399 1.07 0.299 10.66 3.27 0.3 Zone*Site[Cape]*Year 46 17,110 372 0.83 0.953 -53.33 -7.30 -1.7 Res 211 94,172 446 446.31 21.13 14.5 Total 462 790,780 3073.18 b) SIMPER For Within-Zone Similarity Taxon Av.Abund Av.Sim Sim/SD Contrib% Cum.% High Zone Bare Space 3.58 16.77 3.23 26.98 26.98 Balanus 2.57 10.11 2.08 16.27 43.26

Herbivorous snails 3.21 8.62 0.98 13.87 57.13 Limpets 2.62 8.49 1.44 13.66 70.78 Fucoid algae 1.4 4.09 1.05 6.59 77.37 Chthamalus 1.16 3.88 1.87 6.25 83.62 Mussels 1 2.85 1.22 4.58 88.2 Mastocarpus 0.67 1.93 1.12 3.1 91.3 Endocladia 0.52 1.27 0.85 2.04 93.35 Algal crusts 0.56 1.26 0.78 2.03 95.37 Mid Zone Mussels 4.05 26.13 2.74 42.71 42.71 Limpets 3.3 15.62 1.79 25.53 68.23 Predatory snails 1.35 4.59 1.07 7.5 75.73 Bare Space 1.13 4.21 1.33 6.88 82.61 Large barnacles 0.92 3.05 1.16 4.98 87.59 Gooseneck barnacles 0.79 2.31 0.79 3.78 91.37 Balanus 0.5 1.28 0.81 2.09 93.46 Chthamalus 0.31 0.8 0.76 1.3 94.76 Anemones 0.21 0.53 0.69 0.86 95.62 Endocladia 0.3 0.49 0.3 0.8 96.42 Low Zone Bare Space 2.83 9.87 3.29 18.14 18.14 Articulated coralline algae 2.27 7.38 2.48 13.56 31.7 Coralline algae crusts 1.56 4.21 1.59 7.73 39.43 Limpets 1.66 3.72 1.12 6.84 46.27 Hedophyllum 1.36 2.98 0.97 5.47 51.74 Fine branching reds 1.09 2.78 1.37 5.1 56.84 Mazzaella blades 1.08 2.68 1.28 4.92 61.76 Surf grass 1.05 2.08 0.8 3.82 65.58 Anemones 0.87 1.9 0.94 3.5 69.08 Algal crusts 0.83 1.9 1.14 3.49 72.57 https://doi.org/10.1371/journal.pone.0297697.t001 PLOS ONE Resistance of rocky intertidal communities PLOS ONE | https://doi.org/10.1371/journal.pone.0297697 May 29, 2024 8 / 34