Half a century of spread: how trends can inform the phenology of Undaria pinnatifida in California

Abstract

The potential for non-native species to outcompete native species, change ecosystem dynamics and decrease biodiversity necessitates an understanding of their ecological role. Non-native seaweed species (NNSS) can be particularly impactful due to their cryptic life cycles, high fecundity, and tolerance to stressors which could allow rapid spread across coastlines. This literature review summarizes a few well known NNSS in California with a focus on using global literature on Undaria pinnatifida to inform potential trends of habitat use, dispersal, and phenology in this region. Globally, we found that Undaria is widely documented in bays and harbors but there are documented cases of it establishing populations in coastal habitats in exposed rocky reef ecosystems, including California. Using data on thermal tolerance for U. pinnatifida in its native range I found the sea surface temperatures (SST) throughout the west coast of the United States during 2019 are within the thermal tolerance of Undaria with the best SST for gametophytes occurring most frequently in southern California. Using data from the literature, I estimated the potential for Undaria to disperse from known populations in San Diego, CA. These data suggest that Undaria has the potential to disperse into open coastal habitats in this region. This study provides a case for further using pre-existing literature from other regions to guide research conducted in regions of interest that can inform management decisions.