A review of three decades of research on the invasive kelp Undaria pinnatifida in Australasia: An assessment of its success, impacts and status as one of the world's worst invaders

• Published in: Marine environmental research Vol. 131; pp. 243 - 257
• Main Authors: South, Paul M., Floerl, Oliver, Forrest, Barrie M., Thomsen, Mads S.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-10-2017; Elsevier BV
• Subjects: Algae; Anthropogenic factors; Aquaculture; Australasia; Biodiversity; Canopies; Canopy gaps; Canopy-forming species; Case studies; Decoupling; Environmental management; Environmental Monitoring; Eradication; Human influences; Indigenous species; Introduced Species; Invasion pathways; Invasive macroalgae; Invasive species; Kelp; Local communities; Native organisms; NIS; Non-indigenous; Oceans; Open spaces; Plant cover; Population control; Primary production; Rocky shores; Seaweeds; Shores; Temperature tolerance; Turf; Undaria - physiology; Undaria pinnatifida; Vectors; Australasia; Canopy-forming species; Undaria pinnatifida; Invasion pathways; NIS; Non-indigenous; Population control; Eradication; Biodiversity; Kelp; Invasive macroalgae
• ISSN: 0141-1136; 1879-0291
• DOI: 10.1016/j.marenvres.2017.09.015

Marine invasive macroalgae can have severe local-scale impacts on ecological communities. The kelp Undaria pinnatifida is one of the most successful marine invasive species worldwide, and is widely regarded as one of the worst. Here, we review research on Undaria in Australasia, where the kelp is established throughout much of New Zealand and south-eastern Australia. The presence of Undaria for at least three decades in these locations makes Australasia one of the longest-invaded bioregions globally, and a valuable case study for considering Undaria's invasion success and associated impacts. In Australasia, Undaria has primarily invaded open spaces, turf communities, and gaps in native canopies within a relatively narrow elevation band on rocky shores. Despite its high biomass, Undaria has relatively few direct impacts on native species, and can increase community-wide attributes such as primary productivity and the provision of biogenic habitat. Therefore, Australasian Undaria research provides an example of a decoupling between the success and impact of an invasive species. Undaria will most likely continue to spread along thousands of kilometres of rocky coastline in temperate Australasia, due to its tolerance to large variations in temperature, ability to exploit disturbances to local communities, and the continued transfer among regions via vessel movements and aquaculture activities. However, the spread of Undaria remains difficult to manage as eradication is challenging and seldom successful. Therefore, understanding potential invasion pathways, maintaining native canopy-forming species that limit Undaria success, and effectively managing anthropogenic vectors of Undaria spread, should be key management priorities.
•Australasian research on Undaria has documented its spread, mechanisms of invasion, invasion biology, impacts, ecological functions and management.•Undaria pinnatifida has been highly successful at increasing its range in Australasia and can be a conspicuous component of coastal ecosystems.•Evidence of significant direct impacts of this invader on native taxa are scant and conflict with its status as one of the world's worst invaders.•Anthropogenic vectors, artificial substrata, the absence of native canopy algae and facilitation by native species promote invasion success.•Eradication is unlikely to have widespread success, but management might reduce the risk of incursion in pristine areas.•We highlight many research gaps that need to be filled, if a fuller understanding of Undaria invasion is to be achieved.