Bela H. Buck

The genus Laminaria sensu lato : recent insights and developments

This review about the genus Laminaria sensu lato summarizes the extensive literature that has been published since the overview of the genus given by Kain in 1979. The recent proposal to divide the genus into the two genera Laminaria and Saccharina is acknowledged, but the published data are discussed under a ‘sensu lato’ concept, introduced here. This includes all species which have been considered to be ‘Laminaria’ before the division of the genus. In detail, after an introduction the review covers recent insights into phylogeny and taxonomy, and discusses morphotypes, ecotypes, population genetics and demography. It describes growth and photosynthetic performance of sporophytes with special paragraphs on the regulation of sporogenesis, regulation by endogenous rhythms, nutrient metabolism, storage products, and salinity tolerance. The biology of microstages is discussed separately. The ecology of these kelps is described with a focus on stress defence against abiotic and biotic factors and the role of Laminaria as habitat, its trophic interactions and its competition is discussed. Finally, recent developments in aquaculture are summarized. In conclusion to each section, as a perspective and guide to future research, we draw attention to the remaining gaps in the knowledge about the genus and kelps in general.

The offshore-ring: A new system design for the open ocean aquaculture of macroalgae

Mass culture of benthic macroalgae under rough offshore conditions in the North Sea requires rigid culture support systems that cannot only withstand rough weather conditions but can also be effectively handled while at the same time retain the cultured species. Various carrier constructions and different mooring systems were tested. Laminaria saccharina grew on all of these carriers with initially high (up to 14.5% per day) and later decreasing length increments. Longlines, ladder and grid systems had certain disadvantages and these are discussed. The study results led to a new ring carrier (patent pending), first used in 1994/1995, which was gradually improved until 2002. This system now emerges as being superior, since it resists not only rough weather conditions (2 m s−1 current velocity, 6 m wave height) but also permits ease of handling when compared to other constructions. The ring allows various operational modes and can be equipped with culture lines that can be collected offshore or transported to shore facilities for harvesting. The modular nature of the tested ring system lends itself for future use in integrated aquaculture systems located in or attached to offshore wind farms.

MUSSEL CULTIVATION AS A CO-USE IN OFFSHORE WIND FARMS: POTENTIAL AND ECONOMIC FEASIBILITY

More than 50% of the annual worldwide harvest of mussels is produced in Europe. The mussel cultivation in Germany is based on an extensive on-bottom culture and depends entirely on natural resources for food, spat and space. Due to stakeholder conflicts and a lack of spat availability, mussel farmers tend to move offshore where space is not limited and adequate settlement guaranteed. Newcomers – the offshore wind farmers – are covering large areas in the German Bight which in contrast give the opportunity to use these areas in a multifunctional way by accepting mussel cultivation within the wind farms. This study compiles the basic data for offshore mussel cultivation in close vicinity to a designated offshore wind farm in the open sea of the German Bight and employs different case-scenario calculations to illustrate the impact of changing parameter values on overall profitability or non-profitability of this activity. Primary focus is placed on the production of consumer mussels but seed mussel cultivation is also taken into consideration. We show that production of consumer mussels with longline technology is sufficiently profitable even under the assumption of substantial cost increases. This is especially true, if existing capacities could be used. The cultivation of seed mussels depends on the possibility of using existing equipment. A substantial increase of seed mussel prices to at least 0.6 €, given the main cost categories remaining constant, turns this alternative into substantial profitability. This study concludes with providing some recommendations on how favorable terms or actions could further improve profitability of offshore mussel cultivation. Altogether, our results are intended to shed some light on business management topics that future offshore mariculture operators such as traditional mussel farmers should follow in order to be efficient.

The role of iceberg scours in niche separation within the Antarctic fish genus Trematomus

Abstract. Species of the Antarctic fish genus Trematomus occupy different trophic niches. It is not clear, however, whether small-scale variability in benthic community structure affects niche separation. Therefore abundance and biomass of fish were determined and stomach content and food composition were compared in areas affected by iceberg scours and unaffected areas in the Weddell Sea. Trematomus eulepidotus, T. lepidorhinus and T. scotti dominate undisturbed areas, whereas T. nicolai and especially T. pennellii dominate disturbed areas. Total stomach content and number of prey taxa per fish are higher in preferred than in non-preferred areas. These findings indicate that small-scale horizontal patterns caused by iceberg scours play a distinct role in Trematomus niche separation.

Seaweed and Man

Seaweeds have been utilized by man as food and medication for about 14,000 years. The ever rising demand for edible seaweeds and for biochemical components of seaweeds, mainly hydrocolloids like agar, alginate, and carrageenan, has fuelled a large aquaculture industry particularly in Asia. Future expansion of seaweed culture will include suitable farming sites in offshore areas associated with wind farms. Seaweeds as extractive and therefore bioremedial species are moreover an important component in Integrated Multi-Trophic Aquaculture (IMTA), where commercially valuable organisms of different trophic levels are combined in a culturing system resembling a small ecosystem. The employment created by seaweeds and other aquaculture secures an income to millions of people and is therefore of high socioeconomic importance.

Multi-biomarker approach using the blue mussel (Mytilus edulis L.) to assess the quality of marine environments: season and habitat-related impacts.

Using a comprehensive approach, intertidal, near- and offshore sites in the German Bight were analysed for their environmental quality by assessing the health of blue mussels (Mytilus edulis). During a ten month sampling period mussels were studied with a set of biomarkers comprising lysosomal membrane stability and accumulation of lipofuscin, supplemented by biomarkers indicating nutritional status such as neutral lipids and glycogen in the cells of the digestive gland. Data were analysed in relation to sex, gonadal status, condition index and for the presence of parasites, to determine the overall health status of mussels at the respective sites. Mussels from all sites showed clear signs of stress, indicating an inferior environmental quality throughout the southern German Bight. Further, habitat characteristics such as inundation time and growing on- or off-bottom, as well as seasonal factors, can clearly influence the response of biomarkers in mussels exposed to similar levels of chemical environmental stress.

Colonization of an artificial hard substrate by Mytilus edulis in the German Bight

Abstract The colonization of the underwater construction of an offshore research platform in the German Bight by Mytilus edulis was investigated. Mussel abundance, biomass and percentage coverage of the construction were determined from summer 2003 to summer 2005 from different water depths using digital underwater images and scrape samples of the hard substrate fauna. Growth was estimated from shell length distributions. In 2003 settlement of M. edulis was low at the platform mainly due to a temporal mismatch between platform construction and occurrence of competent larvae. In summer 2004 mussel abundance increased remarkably in the intertidal and upper subtidal. Abundance and biomass increased up to 30,000 individuals m−2 and approximately 40 kg m−2 in summer 2005. At the end of the investigation period, the upper part of the platform foundation was completely covered by M. edulis. Lower parts remained sparsely colonized. Mussel growth rates were high under offshore conditions because of favourable environmental conditions and reduced biological constraints. Cumulative effects from wind farm entities are estimated. Mussel accumulations will be an important component in the estimation of ecological implications of offshore wind farming at least at the local scale.

TECHNICAL REALIZATION OF EXTENSIVE AQUACULTURE CONSTRUCTIONS IN OFFSHORE WIND FARMS: CONSIDERATION OF THE MECHANICAL LOADS

The presented study focuses on the development of offshore wind farms in conjunction with open ocean aquaculture within the German Bight. For aquaculture enterprises in the open ocean an extensive cultivation of various species, blue mussels (Mytilus edulis), oysters

Co-location of passive gear fisheries in offshore wind farms in the German EEZ of the North Sea: A first socio-economic scoping

Worldwide the renewable energy sector is expanding at sea to address increasing demands. Recently the race for space in heavily used areas such as the North Sea triggered the proposal of co-locating other activities such as aquaculture or fisheries with passive gears in offshore wind farms (OWFs). Our interdisciplinary approach combined a quantification of spatial overlap of activities by using Vessel Monitoring System and logbook data with a stakeholder consultation to conclude and verify on the actual feasibility of co-location. In the German Exclusive Economic Zone (EEZ) of the North Sea up to 90% of Danish and 40% of German annual gillnet fleet landings of plaice overlapped with areas where OWFs are developed. Our results indicated further that the international gillnet fishery could lose up to 50% in landings within the North Sea German EEZ when OWF areas are closed entirely for fisheries. No spatial overlap was found for UK potters targeting brown crab in the German EEZ. We further identified a number of key issues and obstacles that to date hinder an actual implementation of co-location as a measure in the marine spatial planning process: defining the legal base; implementation of safety regulations; delineation of minimum requirements for fishing vessels such as capacities, quotas, technical equipment; implementation of a licensing process; and scoping for financial subsidies to set up business. The stakeholder consultation verified the scientific findings and highlighted that all those points need to be addressed in a planning process. In the German EEZ we have shown that the socio-economic importance of spatial overlap varies within planning boundaries. Therefore we recommend an interdisciplinary bottom-up approach when scoping for suitable areas of co-location. Hence, an informed marine spatial planning process requires comprehensive and spatial explicit socio-economic viability studies factoring in also ecological effects of OWFs on target species.

Aquaculture Perspective of Multi-Use Sites in the Open Ocean: The Untapped Potential for Marine Resources in the Anthropocene

This volume addresses the potential for combining large-scale marine aquaculture of macroalgae, molluscs, crustaceans, and finfish, with offshore structures, primarily those associated with energy production, such as wind turbines and oil-drilling platforms. The volume offers a comprehensive overview and includes chapters on policy, science, engineering, and economics aspects to make this concept a reality. The compilation of chapters authored by internationally recognized researchers across the globe addresses the theoretical and practical aspects of multiuse, and presents case studies of research, development, and demonstration-scale installations in the US and EU.