Undaria pinnatifida: A case study to highlight challenges in marine invasion ecology and management

Abstract

Marine invasion ecology and management have progressed significantly over the last 30 years although many knowledge gaps and challenges remain. The kelp Undaria pinnatifida, or “Wakame,” has a global non‐native range and is considered one of the world's “worst” invasive species. Since its first recorded introduction in 1971, numerous studies have been conducted on its ecology, invasive characteristics, and impacts, yet a general consensus on the best approach to its management has not yet been reached. Here, we synthesize current understanding of this highly invasive species and adopt Undaria as a case study to highlight challenges in wider marine invasion ecology and management. Invasive species such as Undaria are likely to continue to spread and become conspicuous, prominent components of coastal marine communities. While in many cases, marine invasive species have detectable deleterious impacts on recipient communities, in many others their influence is often limited and location specific. Although not yet conclusive, Undaria may cause some ecological impact, but it does not appear to drive ecosystem change in most invaded regions. Targeted management actions have also had minimal success. Further research is needed before well‐considered, evidence‐based management decisions can be made. However, if Undaria was to become officially unmanaged in parts of its non‐native range, the presence of a highly productive, habitat former with commercial value and a broad ecological niche, could have significant economic and even environmental benefit. How science and policy reacts to the continued invasion of Undaria may influence how similar marine invasive species are handled in the future.

Population genomics of the introduced and cultivated Pacific kelp Undaria pinnatifida: Marinas—not farms—drive regional connectivity and establishment in natural rocky reefs

“…pinnatifida sporophytes are regularly observed attached to boats docking in the studied marinas (authors, personal observation), and microscopic gametophytes are likely to be transported by various means (ropes, hull fouling, ballast water, etc.) via boating activities (Epstein & Smale, 2017b). Human‐mediated spread, notably through shipping (commercial, fishing or leisure boats), has been pointed out as a main vector of spread in Australasia (South et al., 2017, and references herein).…”

“…These 25 localities, distributed across 12 bays, are representative of the present‐day distribution of U . pinnatifida in Brittany (Araújo et al., 2016; Epstein & Smale, 2017b). The sampling focused on neighbouring (i.e., occurring within the same bay) pairs of natural rocky reef and marina habitats whenever possible.…”

“…U. pinnatifida is one of 346 seaweed species that have been classified as invasive (Thomsen, Wernberg, South, & Schiel, 2016). Although being a very successful NIS, its impacts on the shallow coastal communities seem often moderate and/or limited to taxa with similar properties both in Australia and Europe (Epstein & Smale, 2017b; South et al., 2017). …”

Inconspicuous impacts: Widespread marine invader causes subtle but significant changes in native macroalgal assemblages

“…, Irigoyen et al. , , Epstein and Smale ). Overall, our study demonstrates that caution must be used when broadly classifying an invasive species as having limited ecological impacts on recipient communities.…”

“…, De Leij et al. , Epstein and Smale ). These conclusions are, however, variable and context specific, and based largely on observational or correlative results; therefore, the effects of Undaria on recipient communities within this ecoregion could be greatly underestimated (Epstein and Smale and references therein).…”