The expanding range of Undaria pinnatifida in southern New Zealand: distribution, dispersal mechanisms and the invasion of wave-exposed environments
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Very few studies have addressed how the invasive kelp Undaria pinnatifida (Harvey) Suringar spreads beyond initial founding populations in harbours. Surveys of the harbours and accessible areas of open coast throughout southern New Zealand were conducted to determine how far U. pinnatifida populations had extended since initial incursions. Our findings clearly demonstrate that U. pinnatifida is capable of invading native communities and can establish reproductive populations in locations subjected to significant and consistent wave action. The extent of spread from source populations differs between harbours in which it has established. Dispersal is greatest in harbours with long established populations, those where populations have not been strategically managed, harbours with high water exchange with surrounding coastal waters, and where prevailing currents allow establishment of U. pinnatifida on suitable substrata close to harbour entrances. Dispersal along the open coast is primarily achieved by drifting adult sporophytes that are washed up in the rocky intertidal zone. Founding populations are most often found in the intertidal zone, primarily within rockpools. Subtidal transects and observations indicate that U. pinnatifida is well adapted to invade exposed coastlines and can establish within a broad range of niches in wave-exposed areas including rockpools, the low intertidal, shallow subtidal, Macrocystis pyrifera kelp forests, and in low light areas beyond the vertical extent of large native macroalgae. The current range of U. pinnatifida is much greater than expected and appears to be expanding. Due to its ability to grow in a broad range of environments and to form dense monospecific stands, U. pinnatifida has the potential to strongly modify almost all rocky subtidal and intertidal communities in temperate locations.
KeywordsDispersal Disturbance Exotic Incursion Introduced macroalgae Kelp Marine invasion New Zealand Sporophytes Undaria pinnatifida Wave exposure
We thank all of the divers and field assistants involved in this project over the years, in particular Louise Kregting, Daniel Pritchard, Stewart Bell and Wallace Russell. Thanks also to Peter Bannister and Daphne Lee for constructive advice on experimental design and manuscript preparation. We also thank MetOceans Solutions Ltd for access to wave data. This research was supported by the J.S. Watson Conservation Award from the Royal Forest and Bird Protection Society of New Zealand and the Tennant Bequest Fund, Department of Botany, University of Otago.
- Adams N (1994) Seaweeds of New Zealand. Canterbury University Press, Christchurch, New ZealandGoogle Scholar
- Brown S (1999) Dispersal characteristics of the adventive seaweed Undaria pinnatifida in New Zealand. MSc thesis. University of Otago, New ZealandGoogle Scholar
- Brown M, Lamare M (1994) The distribution of Undaria pinnatifida (Harvey) Suringar within Timaru Harbour, New Zealand. Jap J Phycol: 42:63–70Google Scholar
- Hay C, Luckens P (1987) The Asian kelp Undaria pinnatifida (Phaeophyta: Laminariales) found in a New Zealand harbour. NZ J Bot 25:364–366Google Scholar
- Sanderson J (1997) Survey of Undaria pinnatifida in Tasmanian coastal waters, January–February 1997. Report to Tasmanian Department of Marine ResourcesGoogle Scholar
- Sinner J, Forrest B, Taylor M (2000) A strategy for managing the Asian kelp Undaria: final report. Cawthron Report No. 578. Cawthron Institute, New ZealandGoogle Scholar
- Stuart M (2004) Review of research on Undaria pinnatifida in New Zealand and its potential impacts on the eastern coast of the South Island. Department of Conservation Internal Series 166, New ZealandGoogle Scholar
- Thompson G (2004) Mechanisms of invasion and persistence of the invasive kelp Undaria pinnatifida (Harvey) Suringar within intertidal areas of southern New Zealand. PhD Dissertation, University of Canterbury, New ZealandGoogle Scholar
- Wallentinus I (1999) Undaria pinnatifida (Harvey) Suringar. In: Gollasch S, Minchin D, Rosenthal H, Voight M (eds) Case histories on introduced species: their general biology, distribution, range expansion and general impact, pp. 13–19. Department of Fishery Biology, Institute for Marine Science, University of Kiel, GermanyGoogle Scholar