Offshore Multi-Purpose Platforms for Blue Growth.

The European Commission defines “Blue Growth” as a “long term strategy to support sustainable growth in the marine and maritime sectors as a whole” . According to the Food and Agricultural Organization (FAO), the aim of blue growth is to “secure or restore the potential of the oceans, lagoons and inland waters by introducing responsible and sustainable approaches to reconcile economic growth and food security with the conservation of aquatic resources” . This concept goes in line with the expectations of building offshore multi-purpose platforms (MPPs), which are to bring reductions on operational and maintenance costs, create jobs, optimize marine spatial planning, and promote a sustainable use of marine resources (Abhinav et al., 2o20).

During the past decade, different European projects have explored several designs and the feasibility of MPPs. According to Abhinav et al. (2020), most of them have focused mainly on the integration of offshore energy technologies, for example offshore wind farms with wave and/or tidal energy. Few have studied an integration of offshore renewable energy technologies with aquaculture systems. Some examples of projects that incorporate fish farming are the MERMAID and Space@Sea project.

The MERMAID project (2012 – 2015) was funded by the European Union and its main aim was to determine the possibility of developing MPPs in four locations around the European coasts. These locations were the Baltic Sea, the Wadden Sea (Dutch Coast), the Mediterranean Sea and the Atlantic Ocean (Bay of Biscay). For each of these sites, different combinations of technologies were designed. For instance, the conceptual design in the Mediterranean Sea included wave and wind energy extraction with fish farming, whereas, at the Wadden Sea, seaweed and shellfish farming were incorporated instead of fish farming. At the Baltic Sea, the design only included wind extraction combined with fish and seaweed farming. Finally, the location at the Atlantic Ocean was the only one that did not consider any aquaculture system. On the other hand, the three-year Horizon 2020 Space@Sea project started in 2017 and its aim is to provide a design concept of artificially floating islands, that will combine different uses, including energy and transportation hubs, food production (aquaculture) and living space for workers and urban extension.

“Most concepts of these projects (general MPPs projects) have been subjected to numerical modelling studies, a few of them have reached the stage of experimental testing as well” wrote Abhinav and collaborators, indicating that still more research has to be done to determine the technical feasibility of these designs.

Regarding the impacts on the marine environment, several environmental assessment studies have been carried out to determine the individual impact of an activity (offshore wind farms, fishing farms) and also the impact of integrated activities. The main environmental concerns associated with offshore renewable energy extraction are habitat loss, bird or marine mammals collisions, alteration in food webs and biogeochemical cycles, changes in the composition, abundance and biomass of different organisms, changes in the hydrodynamics, noise pollution, electromagnetic emissions and the establishment of non-indigenous species. Noise pollution has been a main concern for marine mammals, both during the construction and operational phase of offshore wind farms, as it could lead to behavioural change or a permanent damage to hearing. “Marine fish and invertebrates may be similarly hampered in terms of communication masking and disturbance, although there is presently no evidence of noise emitted by OWTs (Offshore Wind Technologies) causing physiological damage to fish” pointed out Abhinav and collaborators. Despite the negative impacts, there are potential benefits of offshore renewable energy extraction, such as the creation of new habitats, enhancement of new refuge and feeding grounds and an increase in the abundance of demersal (bottom-dwelling) fish.

Sea-aquaculture can also have multiple impacts on the marine environment. Some of these include increased parasite and pathogens on wild fish stocks, resource competition between wild and escaped cultured fish, genetic dilution in the local wild fish stock due to interbreeding with escaped fish, eutrophication, changes in biogeochemical processes and sea-floor degradation affecting benthic communities. Marine mammals and birds could be affected by aquaculture due to the lethal or aggressive methods used to prevent them predating on cultured fish, such as shooting or exposing them to loud underwater noises. In addition to this, accidental entanglement and habitat displacement are also a threat.

Until today, the dimension of the environmental impacts when offshore renewable energy activities are integrated with aquaculture systems is still poorly understood. Most likely, there are combined effects that will need to be addressed by using a cumulative impact assessment framework. Ecological modelling could also be a useful method for determining cumulative effects. A shortcoming when using some models has been its failure to capture the marine ecosystem dynamics on a large spatial scale, but the Ecopath with Ecosim (EwE) modelling software has been able to overcome this challenge and it is a promising tool for determining cumulative impacts on an ecosystem.

There are also socio-economic aspects that play an important role in the conceptual design of MPPs. It is foreseen that MPPs will be able to create new jobs, help boost the economy and increase the collaboration between stakeholders from different sectors while providing a non-polluting energy source to the population. However, these expectations come hand in hand with several drawbacks. The main concerns of the people regarding these activities are related with visual pollution, noise generation, job displacement, changes in the use of marine space causing a disruption or displacement of other users’ activities (ex. fishing, water sports), the degradation of the marine environment and also increases in electricity prices or taxes.

There are still many obstacles in the way that need to be addressed in order to materialise the idea of MPPs. “Most of the research effort so far has been allocated to the technical aspects, while the socio-economic and environmental aspects have been investigated to a lower extent” wrote the researchers. They call for a more extensive multidisciplinary approach that can help breach the existing knowledge gap about MPPs. Even though, at the moment, there are many uncertainties, MPPs have the potential to help guarantee a sustainable use of our oceans in the future.

References:

Abhinav, K. A., Collu, M., Benjamins, S., Cai, H., Hughes, A., Jiang, B., ... & Recalde-Camacho, L. (2020). Offshore multi-purpose platforms for a Blue Growth: a technological, environmental and socio-economic review. Science of The Total Environment , 138256.

De Luca L.V. (2016). Modelling the Shadow Effect caused by the Growth of the Blue Mussel Mytilus Edulis on Offshore Wind Farms in the North Sea. (Unpublished master’s thesis). Universiteit Gent, Universiteit Antwerpen, Vrije Universiteit Brussel, Brussels, Belgium.

Eikeset, A. M., Mazzarella, A. B., Davíðsdóttir, B., Klinger, D. H., Levin, S. A., Rovenskaya, E., & Stenseth, N. C. (2018). What is blue growth? The semantics of “Sustainable Development” of marine environments. Marine Policy , 87 , 177-179.