Conspicuous decline of Fucus in Kiel Bay (Western Baltic): what are the causes?

Abstract

In the framework of investigations on possible effects of eutrophication on the macrophytobenthos in Kiel Bay (Western Baltic), a large-scale survey of the distribution and occurrence of the genus Fucus was carried out in 1987/88. For large-scale quantitative mapping, underwater television was employed or direct observations from the water surface were made. Species composition and quantitative biomass data were obtained by dredging and SCUBA-diving. Comparison with the results of earlier investigations revealed a drastic decline in Fucus biomass from between 40 000 and 45 000 t wet wt down to only 2400 t wet wt in 1987/88, which means a decrease by 94 to 95 %. Whereas Fucus vesiculosus as well as F. serratus were still frequent at depths below 2 m down to 13 m in the seventies, during our investigation Fucus spp. was not found in water depths greater than 2 m. Possible causes for the observed changes are discussed, and it is concluded that decreased light levels or increased epiphyte growth as a result of eutrophication, and the reduction of substrate for algal growth due to stone fishing and sand deposition, are the main causes for the decline of Fucus spp.

Intersexuality in the porcellanid crab Pisidia longicornis (Crustacea: Decapoda: Anomura: Porcellanidae)

“…In the present work, intersex individuals of Pisidia longicornis were indeed collected in regions regularly affected by pollution caused by sunken oil tankers or by illegal fuel discharges into the sea (VOGT & SCHRAMM 1991) (Table 1). Therefore, it is possible that intersexuality in Pisidia longicornis in this case was caused by environmental contamination.…”

Modeling the effects of abiotic and biotic factors on the depth distribution of Fucus vesiculosus in the Baltic Sea

“…Kautsky et al 1986, Vogt & Schramm 1991, Eriksson et al 1998. Although partial recovery has been observed at some sites in recent years (Nilsson et al 2004), the general pattern of restricted depth penetration of F. vesiculosus in the Baltic Sea seems to persist (Torn et al 2006).…”

“…The fact that the model does not appear to be particularly sensitive to changes in temperature, which, among other factors, controls epibiotic load, corroborates studies ascribing a more important role to shading by phytoplankton in the decline of Fucus spp. than to epibionts, when it comes to plants near their depth limit (Vogt & Schramm 1991, Rohde et al 2008. The more subtle interactions between epibiotic load and its host algae have by no means been covered to an adequate degree here.…”

“…Among other factors, such as direct habitat destruction or increased grazing due to overfishing of the mesograzers' predators, eutrophication is considered to play the most prominent role in this change (Kautsky et al 1986, Eriksson et al 1998, Torn et al 2006. The ways in which high nutrient levels can hinder the propagation and growth of F. vesiculosus are manifold, the most commonly reported being increased water turbidity (Kautsky et al 1986), increased sedimentation rates (Eriksson & Johansson 2003), increased grazing pressure (Kangas et al 1982), direct inhibition of spore settlement and development (Bergström et al 2003), increased epibiotic load (Wahl 1989), and increased competition with ephemeral algae and the blue mussel Mytilus edulis (Vogt & Schramm 1991).Considering all these possible effects of eutrophication on Fucus vesiculosus, one might be tempted to consider the question of its reduced depth penetration as answered. However, the fact that so many mechanisms and functional groups of organisms are involved, some of them, like epibionts, even having been credited with possibly positive effects on the alga (Wahl 2008), makes a reconsideration of this issue seem appropriate.…”

Recovery stages over long-term monitoring of the intertidal vegetation in the ‘Abra de Bilbao’ area and on the adjacent coast (N. Spain)

“…The decline of large perennial algae under the effect of pollution has been extensively reported, e.g. for several species of kelps (Burrows & Pybus, 1971;Borowitzka, 1972;Littler & Murray, 1975), Cystoseira (Golubic, 1970;Munda, 1980Munda, , 1993Sfriso, 1987;Rodrı´guez-Prieto & Polo, 1996;Cormaci & Furnari, 1999;Benedetti-Cecchi et al, 2001;Thibaut et al, 2005;Pinedo et al, 2007), Fucus (Russell, 1974;Vogt & Schramm, 1991;Bonk et al, 1992;Kautsky, H. et al, 1992;Eriksson et al, 2002), Sargassum (Hirose, 1978;Munda, 1993;Thibaut et al, 2005), Ascophyllum (Rueness, 1973;Bonk & Lein, 1978), Hormosira (Brown et al, 1990) or Gelidium sesquipedale (Gorostiaga & Dı´ez, 1996;Dı´ez et al, 2003). These species are good competitors in habitats with low stress and disturbance, but are progressively replaced by stress-tolerant species when pollutants are introduced into the environment.…”