reach 5–8 m during storms. Investigations were resumed in 2002–2004 aiming at
using this new aquaculture technology in conjunction with offshore wind farms
(Buck 2004; Buck and Buchholz 2004a).
To get more insight into the cultivation of plants under hostile conditions in
multi-use with offshore wind farms, several known carrier designs for algal culture
were built and deployed, subsequently resulting in the final modular construction
named the “Offshore-Ring” (Fig. 11.32a–l; Fig. 11.33a–p; see also see also Sect. 3.1
“Offshore Aquaculture with Extractive Species: Seaweed and Bivalves”). The performance of the various test designs under offshore conditions, length changes and,
where possible, the biomass yield of Sugar kelp Saccharina latissima (Laminaria
saccharina) on these constructions were investigated at different locations. The
results are of high importance for the future utilisation of exposed offshore locations
in combination with offshore platforms, especially when considering multi-user
concepts in offshore areas combining wind farm installations (e.g. Buck 2002;
Krause et al. 2003; Buck et al. 2003, 2004).
Experimental offshore farming of Sugar kelp was first conducted in 1994 and
1995 at Helgoland (North Sea, Germany) as well as in 2001 and 2002 near the
island of Sylt and in the outer estuary of the river Weser (17 nautical miles off the
coast of the City of Bremerhaven). The study sites are characterized by various
hydrographic features. Peak wind velocities of ! 6 Beaufort and ! 8 Beaufort were
noted down during years of the experimental studies.
Four different cultivation systems were designed and deployed in the study area
in order to find the most suitable design for offshore use (Buck and Buchholz
2004a). These included longline (Fig. 11.32e), ladder (“tandem longline”)
(Fig. 11.32f), grid (Fig. 11.32g) and a ring-shaped design (Figs. 11.32a and
11.33a–p) for attachment of algae seeded culture lines. Each of these different
constructions varied in mooring design, floatation and culture units. Concrete
blocks of 2.5, 4 and 4.5 t were employed in a single, twin or radial mooring
geometry in order to securely moor the carrier constructions. The ladder and grid
constructions were oriented parallel to the main direction of the tidal current.
Starting from the anchor stones chains with a service load (SL) of at least 8 t were
used to connect the concrete with the mooring line (SL 12 t). The service loads
corresponded to a threefold collapse load. The mooring line itself held the culture
unit, which was designed to float at or 1–1.5 m below the water surface. The
floating system consisted of ball-like floats or pencil-like fenders, which were
connected by ropes to the culture unit to provide sufficient buoyancy. All connections between ropes, chains, floats and concrete blocks contained triple rings
(SL 6 t), shackles (SL 6.5 t), warbles (SL 6.5 t) and thimbles, in case of eyes at
rope ends. The longline design consisted of a 50 m long, horizontal carrier rope
anchored by a 4 t twin mooring system. It served to fasten culture lines perpendicular to the water surface, each kept straight by a concrete weight (2.5 kg)
(Fig. 11.32e). This method had been successfully employed by Kain and Dawes
(1987) and Perez et al. (1992).
Between December 1994 and April 1995, a total of 140 Â 5 m long culture lines
with young Saccharina sporophytes were transferred from the laboratory and
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B.H. Buck et al.
using this new aquaculture technology in conjunction with offshore wind farms
(Buck 2004; Buck and Buchholz 2004a).
To get more insight into the cultivation of plants under hostile conditions in
multi-use with offshore wind farms, several known carrier designs for algal culture
were built and deployed, subsequently resulting in the final modular construction
named the “Offshore-Ring” (Fig. 11.32a–l; Fig. 11.33a–p; see also see also Sect. 3.1
“Offshore Aquaculture with Extractive Species: Seaweed and Bivalves”). The performance of the various test designs under offshore conditions, length changes and,
where possible, the biomass yield of Sugar kelp Saccharina latissima (Laminaria
saccharina) on these constructions were investigated at different locations. The
results are of high importance for the future utilisation of exposed offshore locations
in combination with offshore platforms, especially when considering multi-user
concepts in offshore areas combining wind farm installations (e.g. Buck 2002;
Krause et al. 2003; Buck et al. 2003, 2004).
Experimental offshore farming of Sugar kelp was first conducted in 1994 and
1995 at Helgoland (North Sea, Germany) as well as in 2001 and 2002 near the
island of Sylt and in the outer estuary of the river Weser (17 nautical miles off the
coast of the City of Bremerhaven). The study sites are characterized by various
hydrographic features. Peak wind velocities of ! 6 Beaufort and ! 8 Beaufort were
noted down during years of the experimental studies.
Four different cultivation systems were designed and deployed in the study area
in order to find the most suitable design for offshore use (Buck and Buchholz
2004a). These included longline (Fig. 11.32e), ladder (“tandem longline”)
(Fig. 11.32f), grid (Fig. 11.32g) and a ring-shaped design (Figs. 11.32a and
11.33a–p) for attachment of algae seeded culture lines. Each of these different
constructions varied in mooring design, floatation and culture units. Concrete
blocks of 2.5, 4 and 4.5 t were employed in a single, twin or radial mooring
geometry in order to securely moor the carrier constructions. The ladder and grid
constructions were oriented parallel to the main direction of the tidal current.
Starting from the anchor stones chains with a service load (SL) of at least 8 t were
used to connect the concrete with the mooring line (SL 12 t). The service loads
corresponded to a threefold collapse load. The mooring line itself held the culture
unit, which was designed to float at or 1–1.5 m below the water surface. The
floating system consisted of ball-like floats or pencil-like fenders, which were
connected by ropes to the culture unit to provide sufficient buoyancy. All connections between ropes, chains, floats and concrete blocks contained triple rings
(SL 6 t), shackles (SL 6.5 t), warbles (SL 6.5 t) and thimbles, in case of eyes at
rope ends. The longline design consisted of a 50 m long, horizontal carrier rope
anchored by a 4 t twin mooring system. It served to fasten culture lines perpendicular to the water surface, each kept straight by a concrete weight (2.5 kg)
(Fig. 11.32e). This method had been successfully employed by Kain and Dawes
(1987) and Perez et al. (1992).
Between December 1994 and April 1995, a total of 140 Â 5 m long culture lines
with young Saccharina sporophytes were transferred from the laboratory and
306
B.H. Buck et al.