Description: The impetus for this study was the mass bleaching event of giant clams in 1997¯1998 at several reefs in the Great Barrier Reef (GBR,Australia). From September until December 1999, the study investigated the effects of high light intensities and increased temperatureaccompanied by a nutrient limitation on the metabolism of Tridacna gigas, to test, if these environmental changes can induce bleaching. In a50-day trial similar conditions of the mass bleaching event were imitated stressing clams, collected from Orpheus Island and Nelly Bay, by atwo- to threefold light intensity and an increased temperature of 4¯6 °C. The objectives of the experiments were to determine whether highlight intensities can induce changes in chlorophyll content or alter zooxanthella cell sizes and populations in the tissue. After 50 days ofexposure to high light intensity the mantle tissue of stressed clams exhibited a decreased number of zooxanthellae per unit area from19.8 ± 0.8 (× 107·cm¯2) to 0.2 ± 0.2 (× 107·cm¯2) (mean ± CL). Additionally, the average cell size of zooxanthellae were downsized from7.4 ± 0.1 m to 5.3 ± 0.1 m (mean ± CL). Subsequently, the chlorophyll content of both, chl a and chl c1, declined as well, chl a from192 ± 4 to 0.1 ± 0.1 g·ml¯1 and chl c1 from 145 ± 6 to 0 g·ml¯1 (mean ± CL). This study shows that increased light intensity andtemperature are the main causes for bleaching in giant clams. Thus, the study confirmed the four major aspects involved in bleaching: (1)loss of symbiotic algae, (2) decrease of chl a/c1 in the remaining symbiotic algae, (3) retention of small zooxanthellae in the tissue and (4)release of ammonium (NH4+) into the water column while nutrient uptake of ammonium was largely blocked.

Description: The use of the North Sea is extremely multi-faceted and high competitive.Within the vast variety of regulations within the EU and in Germany, theregulative framework relevant to aquaculture is yet incomplete. This paperprovides a short summary of the current legislative framework existent oninternational, national, and regional levels, which pertain aquaculturedevelopment in Germany. Following, it highlights the question of decisionmakingin the coastal zone within an integrated coastal zone management(ICZM) approach. It can be shown, that there is an ample need forsufficient regulations to optimise the management of the marineresources, especially in respect to further ecological and socio-economicsound aquaculture development. Within the ICZM framework foraquaculture management in the North Sea, we propose a scheme forfurther development and the establishment of an independentregulatory/advisory body, which encompasses all spatial levels.Additionally, we show which tools, such as DSS (e.g. GIS) and activeparticipation, could be used in such a scheme in the decision makingprocess and what outcomes at which stage is to be expected. The articlecloses with a call for integrative action in Germany for the furtherpromotion of aquaculture development by endorsing the idea of ICZM inorder to sustain its economic potential as alternative livelihood for coastalcommunities.

Description: This chapter focuses on the current situation of aquaculture development in the North Sea region in the light of world-wide decline of wild fish stocks and increasing consumer demand for seafood. With 1.4 Mill. metric tons of annual production the culture of fish, especially salmon and trout, is the most commonly intensively employed aquaculture sector within the North Sea region. This has resulted in several environmental problems, such as eutrophication of the adjacent water column of the aquaculture facility due to food pellets and faeces, as well as the spread of diseases and parasites. The major shellfish species, which is extensively cultured in many countries along the North Sea, is the blue mussel, followed by the pacific oyster. Several shellfish culture techniques have emerged, which are described and discussed in respect to impacts on the environment as well as their future prospective. The chapter closes with a call for integrative action among the North Sea region states for the further promotion of ecological and socio-economic sound aquaculture development by endorsing the idea of ICZM in order to sustain its economic potential as alternative livelihood for coastal communities.

Description: In the offshore region of Germany, human activity is increasing in type and intensity. Larger portions of the sea are sectioned off, dedicated for specific, often exclusive uses that cause rising conflicts between interests groups. One solution calls for stakeholder integration and the multifunctional use of space. This article focuses on two examples, offshore wind farms and open ocean aquaculture. It analyses their potential synergies within a co-management approach. It can be shown, that an integrated co-management strategy for offshore regions requires very different sets of rights and duties, as well as holding different types of conflicts, constrains and alliances, some of which are illustrated for the presented case study. The article closes with the conclusion that an integrated regulative framework is the most important basic precondition for a multifunctional utilisation of offshore areas and its sustainable development.