The Introduced Alga Undaria pinnatifida (Laminariales, Alariaceae) in the Rocky Shore Ecosystem of the St Malo Area: Growth Rate and Longevity of the Sporophyte

Abstract

Corresponding authorAs a result of the deliberate introduction of Undaria pinnatifida (Harvey) Suringar into the Rance Estuary for aquaculture purposes, this kelp has now established itself naturally in the coastal area around St Malo. A population of U. pinnatifida in the Dinard area was subjected to a monthly monitoring programme, conducted in the lower eulittoral zone during low water of Spring tides. Tagging of thalli and punching of holes on the blades were methods used to estimate growth rate. Five parameters were measured: total length, stipe length, midrib width, sporophyll number and sporophyll width. During the 20 months of this study, 4 series of thalli (two per year) developed successively, in spring and autumn. Thalli appeared throughout the year, although very few were present during a period of three weeks, from the end of August to mid-September. Maximal daily growth rates occurred in MarchϪApril (21 mm/day) for spring thalli appearing from January to March, and in November (18 mm/day) for those appearing in October. The highest growth rate was observed both in the spring rise and autumnal fall of temperature and illumination. Thalli that appeared in autumn and winter produced the widest sporophylls. Thalli that appeared in spring and early summer gave rise to sporophylls less wide but more numerous. The maximal life-span noted in the field was 222 days (about 7.5 months); but most had a life-span of about 6 months. Maximal size observed was 1.90 m, with 1.470 g wet weight and 190 g dry weight.

The structure of biogenic habitat and epibiotic assemblages associated with the global invasive kelp Undaria pinnatifida in comparison to native macroalgae

“…As such, U. pinnatifida has become an integral component of the shallow subtidal ecosystem, with regards to ecological functions such as biogenic habitat provision and primary production, at least from early spring until mid-summer. Although some U. pinnatifida sporophytes have been observed recruiting in the autumn and persisting through the winter, as is the case in Brittany, France (Castric-Fey et al, 1999) this cohort would appear to be spatially restricted and/or very scarce given that sporophytes were not recorded during the December surveys at either Firestone Bay or additional sites within Plymouth Sound (Smale, unpublished data). Given that U. pinnatifida is thought to be competitively inferior to native kelps in the northeast Atlantic (Floc'h et al, 1996;Farrell and Fletcher, 2006), it has seemingly dispersed from artificial habitats and colonized subtidal rocky reefs in Plymouth Sound relatively quickly (i.e.…”

Macro-environmental modelling of the current distribution of Undaria pinnatifida (Laminariales, Ochrophyta) in northern Iberia

“…Therefore, although temperatures cannot, in principle, and by itself explain the absence of colonisation in the east of the Cantabrian coast, we still consider that it is an important factor contributing to its presence. In fact, Castric-Fey et al (1999b) described the temperature range for possible sporophyte recruitment in France as 5-20°C, recruitment peaks occurring at 13-17°C, which is totally outside the sea surface temperature range in the eastern Cantabrian coast.…”

Comparison of photobioreactors and optimal light regime for rapid vegetative propagation of transgenic Undaria pinnatifida gametophytes

“…1,2 Undaria pinnatifida has a heteromorphic life cycle with an alternation between a microscopic haploid gametophyte generation and a macroscopic diploid sporophyte generation. Sporophytes have long been an important food resource in Japan due to its high levels of protein, minerals, vitamins and dietary fiber.…”