The status of brown macroalgae Fucus spp. and its relation to environmental variation in the Finnish marine area, northern Baltic Sea

A large-scale loss of the habitat-forming

macroalgae Fucus vesiculosus was reported around the

Baltic Sea in the 1980’s, but only relatively local studies

have reported its current status. We studied recent

comprehensive mapping data in the Finnish marine area

and compared reported Fucus occurrences in relation to its

potential, to find out its current status on a larger scale. We

also investigated the effects of water quality on Fucus

occurrence and its depth penetration. Our results show that

the status of Fucus is better in the Gulf of Bothnia than in

the Gulf of Finland, both in terms of its occurrence rate and

its depth distribution. Despite high potential in the outer

Archipelago Sea, the status of Fucus is poor. The Fucus

occurrence patterns are mainly related to salinity, exposure

and Secchi depth, all positively affecting the Fucus

occurrence rate and/or the lower limit of the Fucus zone.