Long-term decline and recent recovery of Fucus populations along the rocky shores of southeast Sweden, Baltic Sea

Abstract

The Fucus populations on rocky shores along 300 km of the coastal waters of southeast Sweden in the Baltic proper have been studied since 1984 at a number of fixed sites as part of monitoring programmes. This paper describes changes in distribution and abundance of F. vesiculosus and F. serratus during the period 1984-2001. Sheltered sites showed a consistent temporal and spatial pattern of Fucus spp. distribution over a coastline of 300 kilometres. The depth penetration and abundance of Fucus spp. increased during the 1980s. Around 1990 the development reversed as a consequence of grazing and in 1997 many sites were almost devoid of Fucus spp. Since 1998 both abundance and depth penetration have increased again, possibly as a result of local measures against eutrophication. Exposed sites, on the other hand, lost their Fucus populations at the beginning of the 1990s, and they have not recovered. Extended field studies lead us to deduce that the fixed sites referred to above were representative of the Fucus populations in the area investigated. Major declines, both at sheltered and exposed sites, are attributed to grazing by the isopod Idotea baltica. The populations of I. baltica may have been favoured by the continuing eutrophication of the Baltic, a series of mild winters in the 1990s, and a contemporary decline in some potential predators.

GENETIC STRUCTURE IN POPULATIONS OF FUCUS VESICULOSUS (PHAEOPHYCEAE) OVER SPATIAL SCALES FROM 10 M TO 800 KM1

“…Local extinction of stands of F. vesiculosus in the Baltic Sea (Vogt and Schramm 1991, Nilsson et al. 2004) has already prompted a few restoration projects (L. Kautsky, personal observation).…”

“…1982, Kautsky et al. 1986) and even local extinctions (Nilsson et al. 2004), both a likely consequence of increased anthropogenic stress, such as eutrophication, and possibly of the cascade effects of overfishing or other factors changing the fish community (Nilsson 2004).…”

Phenotypic variation in sexually and asexually recruited individuals of the Baltic Sea endemic macroalga Fucus radicans: in the field and after growth in a common-garden

“…Isopod abundance is low in the Bothnian Sea compared to in the Baltic Proper [28], and grazing pressure from isopods seems mostly low or absent in most areas where F. radicans is present [18]. In addition, phlorotannin production is known to be costly [29], this study], and, thus there is probably a trade-off favouring a low phlorotannin production in areas of low grazing pressure.…”

Model simulation of seasonal growth of Fucus vesiculosus in its benthic community

“…The simulated impact of herbivory on Fucus growth rates was high in summer and originates mainly from its highly seasonal nature. The importance of transitory peaks in the number of herbivores, arising from unusually favorable conditions (e.g., warm summer conditions), and their effect on Fucus (Nilsson et al ) seem to be well implemented in the model.…”