Fucus serratus (Linnaeus 1753), (Phaeophyta) Toothed wrack

Compiled by: Mats Lindegarth, Sweden

Fucus serratus at 1 m depth in Bohuslän on the Swedish west coast. Photo by Martin Isæus, AquaBiota Water Research.

1. Description of the habitat /autecology of the species

The toothed or serrated wrack, Fucus serratus L., is widely distributed in the Arctic and the northern Atlantic. In the Baltic Sea, F. serratus is common as single stands or belts in rocky habitats at depths of 0.5 to 10 m. It occurs in salinities down to c. 7 psu.

 2. Distribution (past and present)

F. serratus is distributed from the Kattegat into the southern Baltic Proper. In Swedish areas the occurrence of F. serratus declines gradually northward and on the border to the northern Baltic Proper it disappears. Despite some changes in overall salinity in the Baltic Proper, the large-scale distribution of F. serratus appears not to have changed radically during the last 100 years. Nevertheless, temporary local and regional changes in cover and occurrence have been observed in sheltered and exposed areas. These changes have been attributed to eutrophication and extensive grazing during mass occurrences of the isopod Idothea baltica.

3. Importance (sub-regional, Baltic-wide, global)

F. serratus is an important phytobenthic species in the Baltic coastal zone. It is widely distributed and highly productive on rocky shores, where Fucus belts play an important structuring role and have a positive effect on biodiversity.

4. Status of threat/decline

F. serratus is considered threatened and/or in decline in the Bay of Mecklenburg and the Kiel Bay.

5. Threat/decline factors

Observed changes in occurrence and depth range have often been attributed to eutrophication. In the Baltic, the distribution of F. serratus is limited towards the north-east by salinity. Therefore, any long-term anthropogenic or natural changes in salinity may severely affect the distribution of the species. Furthermore, some evidence suggests that high densities of the grazing isopod, Idothea baltica, may have severe effects on the occurrence of F. serratus. Therefore, persistent changes in the trophic structure of the Baltic ecosystem may be important also for F. serratus.

6. Options for improvement

Combating eutrophication and maintaining stable conditions in the Baltic ecosystem may improve the prospects for a favourable conservation status of F. serratus.

7. References

HELCOM, 2007. HELCOM lists of threatened and /or declining species and biotopes/habitats in the Baltic Sea area. HELCOM-Baltic Sea Environment Proceedings 113, Helsinki Commission. 17 pp.

Jackson, A., 2007. Fucus serratus. Toothed wrack. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 14/09/2007]. Available from: http://www.marlin.ac.uk/species/Fucusserratus.htm

Malm, T., Kautsky, L., Engkvist, R., 2001. Reproduction, recruitment and geographical distribution of Fucus serratus L. in the Baltic Sea. Bot. Mar. 44, 101-108.

Nilsson, J., Engkvist, R., Persson, L.-E., 2004. Long-term decline and recovery of Fucus populations along the rocky shores of southeast Sweden, Baltic Sea. Aquat. Ecol. 38, 587-598.

Nordiska Ministerrådet 2001. Kustbiotoper i Norden: hotade och representativa biotoper. TemaNord 2001:536. ISBN 92-893-0626-2. pp. 345. (in Swedish).