Resistance of rocky intertidal communities to oceanic climate fluctuations

1) time lags in responsiveness deriving from longevity of component species and 2) impor- tance of top-down trophic forcing. First, many species in our system are long-lived and possess strong regenerative capabilities. For example, once they survive the extremely high mortality rates experienced as larvae and juveniles, many invertebrates in our system can live for years, decades, and even centuries. Some examples include sea anemones (Anthopleura xanthogram- mica and A. elegantissima) that may live >100 years [103], sea urchins (Strongylocentrotus pur- puratus) that likely live several decades [104], and mussels and large barnacles (Mytilus californianus and Semibalanus cariosus) that can live at least ~15 years [105,106]. Similarly, many of the dominant algae die back annually or when stressed, but can quickly regrow from their holdfasts [107–110]. So, while changes in climate mode or stress events can have sub- lethal physiological effects on these species [64,111–114], this may not translate into long-last- ing changes in abundance. In addition, long-life spans of many component species mean that climate-sensitive processes like recruitment and growth may take years to translate into com- munity change. Ultimately, long-life span and perennating capabilities suggest that sensitivity at the community level may lag behind the changes in oceanic climate and may not be detect- able for years to come. Second, climate-sensitive rates of recruitment and growth of individuals versus their sur-

vival in the face of top-down trophic forcing may influence the disconnect between ecological processes and community structure. For example, recruitment and/or growth rates of short- lived species of barnacles and mussels (B. glandula, C. dalli, and the mussel M. trossulus) at some of our sites (primarily sites on Cape Perpetua) can be extremely high [20,48,54,62,115]. However, while adult cover of these weedy species may spike as a result, these increases do not usually persist more than a few weeks to months due to high annual mortality from predation Fig 10. Correlations of the rate (vector lengths in Fig 4d–4f) of community change with significant environmental drivers (identified by models in Table 3) in Oregon and northern California from 2007–2020. Focal comparisons included the a) rate of change in the mid zone with Multivariate El Niño Southern Oscillation Index (mean ENSO) zone, b) rate of change in the mid zone with the years since the initial sea star wasting disease outbreak (Yrs since SSWD), and c) rate of change in the low zone with the maximum daily air temperature (Max Air Temp). https://doi.org/10.1371/journal.pone.0297697.g010 PLOS ONE Resistance of rocky intertidal communities PLOS ONE | https://doi.org/10.1371/journal.pone.0297697 May 29, 2024 23 / 34