Project: Offshore Aquaculture

Contact Person: Prof. Dr. Bela H. Buck, Susanne Spahic, Prof. Dr. Victor Smetacek

Status: finished

First offshore aquaculture project as a multifunctional use of offshore wind farms

Background

The overall highly competitive use of North Sea areas by shipping (trade or private), gravel extraction, recreational activities, offshore wind farms, dredge spoil disposal, marine missions, fisheries, oil and gas explorations/exploitations, oil pipelines and cables as well as nature reserves and other marine and coastal protected areas has highlighted the spatial competition every stakeholder faces (Fig. 1 & 2, BSH). Thus, the need for sufficient regulations to optimise the management of the resources within a multi-use context, in which aquaculture is an equal user, is evident.

The emerging branch of marine aquaculture faces the problem of every other newcomer for which functional needs have not previously been considered. One option to minimize conflicts and interactions with other resource users is to explore the potential of offshore farming systems. However, when going offshore, a multifunctional sharing of marine waters, such as combining offshore wind farms with open ocean aquaculture, could be a solution to minimise further spatial conflicts. Provided joint and interactive planning is initiated at an early date to limit additional environmental impacts, interactions with other users are promoted.

: Fig. 2: All uses in the German North Sea area (BSH)

: Fig. 1: Applications for offshore wind farms (BSH)

Going Offshore

Germany considers the combination of environmentally friendly wind-driven power generation with the environmental enhancement that aquaculture offers as a very important opportunity for the development of a multiple resource use concept. Our research concentrates on extensive "Open Ocean Aquaculture" systems.

Multifunctional use of offshore installations

Culture Conditions and Candidates

In these offshore locations the degree of mixing within the water column can be presumed to be high, as the water masses are continuously moved and exchanged through tidal currents and are far away from urban locations, which results in a continues supply of clean water with good O2-conditions. Furthermore, the concentration of pollutants, pesticides and near-surface agents can be considered as minimal. The influence of salinity and temperature in these areas are similar at all locations and lay in the scope of tolerance of some candidates. However, the hydrodynamic conditions require resistant species, which can withstand currents of about 1-2 m/s and mean wave heights of about 2-3 m (18 m every 100 years), respectively.

There are a variety of candidates, which can be cultivated under such hydrodynamic and environmental conditions within the North Sea and hold large potentials on the German market. Within the group of bivalves, especially the blue mussel (Mytilus edulis) and oysters (Ostrea edulis & Crassostrea gigas) (Fig. 3 & 4) are assumed to withstand those conditions. Additionally, the mussels and oysters show a high marketing potential on the German market. In the group of seaweeds, kelp can resist those offshore conditions and has commercial potential. The macroalgae Laminaria saccharina and Palmaria palmata are candidates for this project (Fig. 5 & 6).

: Fig. 6: The macroalgae
Palmaria palmata

: Fig. 5: The macroalgae Laminaria saccharina

: Fig. 4: The oyster Crassostrea gigas (juveniles)

: Fig. 3: The blue mussel Mytilus edulis

Project Setup

In cooperation with the Research Center Terramare (Wilhelmshaven), all marine areas, where wind farms are planned (Fig. 7), were equipped with mooring systems to test the settlement and/or growth of candidate species in January 2003. These mooring systems (Fig. 8) were equipped with two culture testing facilities, so called "LAM"-frames, in a depth of 4-6 m below the water surface. The top frame had a holding unit for the culture of Laminaria saccharina and oysters (Ostrea edulis, Crassostrea gigas); at the lower frame mussel larval collectors and juveniles of Mytilus edulis were installed. On monthly expeditions all these moorings are visited and samples taken, such as plankton loads, growth parameters, oceanographic data, etc. The outcomes of this project will provide an expertise for the feasibility of offshore wind farm areas for the extensive culture of bivalves and seaweed.

In the near future the installation of the planned offshore wind turbines will provide an opportunity to test various open ocean culture systems.