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Henrice Jansen


M.Sc.: 2004 - 2005

Co-supervisor: Dr. J. Verreth, University of Wageningen, The Netherlands

Present occupation: Ph.D. candidate, University of Wageningen, The Netherlands

Thesis: Monitoring of early stages in the kelps Alaria esculenta and Laminaria digitata

henrice jansen's picture Henrice Jansen deploying lines of kelps at an IMTA site, Bay of Fundy, Canada (photo: Manav Sawhney).

Abstract: Both Laminaria digitata and Alaria esculenta reproduce sexually and exhibit a diplohaplontic life cycle. Besides few morphological alternative expressions in some stages, both Alaria esculenta and Laminaria digitata follow in general the development in kelp as stated by McKay (1933). The development of Alaria esculenta follows a more or less stepwise pattern, while development of Laminaria digitata is more gradual. Both reach the sporophyte stage within 35 days. A clear morphological difference between species can be observed, as early as 2-2.5 mm, when examining the microscopic sporophytes. Alaria esculenta shows a more elongated cylindrical shape while Laminaria digitata has a more rounded shape. Microscopic sporophytes (>0.1mm) of Laminaria digitata show a denser part in the bottom of the sporophyte, which might indicate the early formation of the stipe. Laminaria digitata suffered considerably more contaminants than Alaria esculenta. This might be explained by the fact that the collected sori were damaged which might serve as a suitable environment for a number of epiphytic and endophytic species. The extreme mucilaginous slime covering observed on Laminaria digitata might also be a source of contamination. It is not sure if this slime covering also interacts with the development of the kelps.