Stone extraction and its importance for the re-establishment of Fucus versiculosus along its historical reported depths

The glacial deposits represent the main hard substrata for macroalgae development in the Baltic Proper. The limited data from the Baltic Sea have until recently hindered investigation about the importance of these deposits for long-term establishment of specific macroalgae communities. Between 1850 and 1970 stone extraction ('stone fishery') were an important source of money income for the local fishery and industry. Large stones were craned with assistance from divers and used for port and road construction. At least 3.5 million tons of stones were extracted in ecologically sensitive areas along the coast of Schleswig-Holstein. Fucus spp. declined from 1950 to 1990 by nearly 95 % in the Kiel Bight due to eutrophication and loss of habitat. While the bladder wrack Fucus vesiculosus is still abundant in the upper 2 meters of the littoral zone, it lacks in all other historical reported depths up to 8 ms. Most probably,Fucus will be one of the target species for the new EU Water Framework Directive; however the man-made absence of glacial deposits in wide areas of the near-shore environment may complicate the calculation of depth zonation of Fucus in future monitoring programs. The authors discuss the loss of habitat due to stone fishery as well as the potential for the re-establishment of Fucus below its current depth zonation. It is challenged if Fucus is able to spread out without (1) the insertion of additional substrata or (2) artificial transplantation from the uppermost eulittoral zone.