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Chemical settlement inhibition versus post-settlement mortality as an explanation for differential fouling of two congeneric seaweeds
Stockholm University, Faculty of Science, Department of Botany.
2004 (English)In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 138, no 2, 223-230 p.Article in journal (Refereed) Published
Abstract [en]

It has been proposed that seaweed secondary metabolites, e.g. brown algal phlorotannins, may have an ecologically important function as a chemical defence against epiphytes, by acting against colonisation of epiphytic organisms. We tested whether the low epiphytic abundance on the invasive brown seaweed Fucus evanescens, compared to the congeneric F. vesiculosus, is due to a more effective chemical defence against epiphyte colonisation. A field survey of the distribution of the common fouling organism Balanus improvisus (Cirripedia) showed that the abundance was consistently lower on F. evanescens than on F. vesiculosus. However, contrary to expectations, results from experimental studies indicated that F. vesiculosus has a more effective anti-settlement defence than F. evanescens. In settlement experiments with intact fronds of the two Fucus species, both species deterred settlement by barnacle larvae, but settlement was lower on F. vesiculosus both in choice and no-choice experiments. Phlorotannins from F. vesiculosus also had a stronger negative effect on larval settlement and were active at a lower concentration than those from F. evanescens. The results show that Fucus phlorotannins have the potential to inhibit settlement of invertebrate larvae, but that settlement inhibition cannot explain the lower abundance of the barnacle Balanus improvisus on F. evanescens compared to F. vesiculosus. Assessment of barnacle survival in the laboratory and in the field showed that this pattern could instead be attributed to a higher mortality of newly settled barnacles. Observation suggests that the increased mortality was due to detachment of young barnacles from the seaweed surface. This shows that the antifouling mechanism of F. evanescens acts on post-settlement stages of B. improvisus.

Place, publisher, year, edition, pages
2004. Vol. 138, no 2, 223-230 p.
Keyword [en]
Antifouling, Balanus improvisus, Epiphytes, Fucus, Phlorotannins
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-22997DOI: 10.1007/s00442-003-1427-9OAI: diva2:189872
Available from: 2004-05-06 Created: 2004-05-06 Last updated: 2011-06-23Bibliographically approved
In thesis
1. Marine Seaweed Invasions: the Ecology of Introduced Fucus evanescens
Open this publication in new window or tab >>Marine Seaweed Invasions: the Ecology of Introduced Fucus evanescens
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biological invasions are an important issue of global change and an increased understanding of invasion processes is of crucial importance for both conservation managers and international trade. In this thesis, I have studied the invasion of the brown seaweed Fucus evanescens, to investigate the fate and effect of a perennial, habitat-forming seaweed introduced to a coastal ecosystem. A long-term study of the spread of F. evanescens in Öresund (southern Sweden) showed that the species was able to expand its range quickly during the first 20 years after the introduction, but that the expansion has been slow during the subsequent 30 years. Both in Öresund and in Skagerrak, the species is largely restricted to sites where native fucoids are scarce. Laboratory experiments showed that the restricted spread of F. evanescens cannot be explained by the investigated abiotic factors (wave exposure and salinity), although salinity restricts the species from spreading into the Baltic Sea. Neither did I find evidence for that herbivores or epibiota provide biotic resistance to the invader. On the contrary, F. evanescens was less consumed by native herbivores, both compared to the native fucoids and to F. evanescens populations in its native range, and little overgrown by epiphytes. Instead, the restricted spread may be due to competition from native seaweeds, probably by pre-occupation of space, and the establishment has probably been facilitated by disturbance.

The studies provided little support for a general enemy release in introduced seaweeds. The low herbivore consumption of F. evanescens in Sweden could not be explained by release from specialist herbivores. Instead, high levels of chemical anti-herbivore defence metabolites (phlorotannins) could explain the pattern of herbivore preference for different fucoids. Likewise, the low epibiotic colonisation of F. evanescens plants could be explained by high resistance to epibiotic survival. This shows that colonisation of invading seaweeds by native herbivores and epibionts depends on properties of the invading species. The large differences between fucoid species in their quality as food and habitat for epibionts and herbivores imply that invasions of such habitat-forming species may have a considerable effect on a number of other species in shallow coastal areas. However, since F. evanescens did not exclude other fucoids in its new range, its effect on the recipient biota is probably small.

Place, publisher, year, edition, pages
Stockholm: Botaniska institutionen, 2004. 44 p.
biological invasions, marine, seaweed, algae, herbivory, enemy release hypothesis, phlorotannins, anti-fouling, Fucus evanescens
National Category
urn:nbn:se:su:diva-132 (URN)91-7265-870-3 (ISBN)
Public defence
2004-05-28, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00
Available from: 2004-05-06 Created: 2004-05-06Bibliographically approved

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