Volume 63, Issue 1 - Special issue: Seaweed resources of the world: a 2020 vision. Part 3 / Issue editors: Alan T. Critchley, Anicia Hurtado, Leonel Pereira, Melania Cornish, Danilo Largo and Nicholas Paul

Seaweed resources play an increasingly important role in European Blue Growth and Bioeconomy strategies and European production is anticipated to increase dramatically with the continued up-swing of global market interests in seaweed resources. As a consequence, there is a need to ensure the environmental sustainability of future aquaculture activities, as reported in the PEGASUS white paper. The present article summarizes the published PEGASUS guidelines developed in the framework of the COST Action Phycomorph, for the future development of this sector. This includes the advances made in this important arena of applied phycology taking into account scientific, technical, environmental, legal and socioeconomic dimensions. Challenges, bottlenecks and risks are identified and presented with a special focus on production issues regarding productivity, breeding, choice of appropriate cultivars, disease and pests and also the risk of using non-indigenous and invasive species as candidates for cultivation. The barriers for long-term, sustainable exploitation are also examined including harmony with the European “Nutrition and Health Regulations” necessary in order to ensure food safety. The PEGASUS guidelines provide scientific recommendations required to address the above issues and to provide science-based advice to policymakers, managers and industries for the sustainable development of industrial-scale seaweed aquaculture in Europe and beyond.

This review focuses on the diversity of French tropical overseas macroalgae and their biotechnological applications. After listing the specific diversity, i.e. 641 species in French Antilles in the Atlantic Ocean, 560 species in the Indian Ocean, and 1015 species in the South Pacific Ocean, we present the potential of their metabolites and their main uses. Among the great diversity of metabolites, we focus on carbohydrates, proteins, lipids, pigments and secondary metabolites, in particular terpenes and phenolic compounds. The main applications of reef macroalgae are described in human and animal consumptions, phycocolloids extraction, production of active ingredients for health, cosmetics, agriculture, and bioremediation. For each application, we list what has been done, or will be done in French tropical overseas territories and point out the challenges faced when using this chemo-diversity, and problems linked to their exploitation. Finally, we discuss challenges to develop seaweed farming, their uses in carbon sequestration and resilience to global change, their uses for alternative proteins together with the production of bioenergy and biomaterials. As a conclusion, we encourage the research on the chemo-diversity of French reef macroalgae for industrial applications as these organisms represent a reservoir of active ingredients that is still insufficiently explored.

The ability to map and monitor the macroalgal coastal resource is important to both the industry and the regulator. This study evaluates topo-bathymetric lidar (light detection and ranging) as a tool for estimating the surface area, height and biomass of Ascophyllum nodosum , an anchored and vertically suspended (floating) macroalga, and compares the surface area derived from lidar and WorldView-2 satellite imagery. Pixel-based Maximum Likelihood classification of low tide satellite data produced 2-dimensional maps of intertidal macroalgae with overall accuracy greater than 80%. Low tide and high tide topo-bathymetric lidar surveys were completed in southwestern Nova Scotia, Canada. Comparison of lidar-derived seabed elevations with ground-truth data collected using a survey grade global navigation satellite system (GNSS) indicated the low tide survey data have a positive bias of 15 cm, likely resulting from the seaweed being draped over the surface. The high tide survey data did not exhibit this bias, although the suspended canopy floating on the water surface reduced the seabed lidar point density. Validation of lidar-derived seaweed heights indicated a mean difference of 30 cm with a root mean square error of 62 cm. The modelled surface area of seaweed was 28% greater in the lidar model than the satellite model. The average lidar-derived biomass estimate was within one standard deviation of the mean biomass measured in the field. The lidar method tends to overestimate the biomass compared to field measurements that were spatially biased to the mid-intertidal level. This study demonstrates an innovative and cost-effective approach that uses a single high tide bathymetric lidar survey to map the height and biomass of dense macroalgae.

Due to low salinity and lack of hard substrata, the Baltic Sea and Kattegat area and German and Danish North Sea coasts are characterized by a relatively low diversity of seaweeds. At the same time the areas are severely eutrophicated, which has caused extensive shifts in macroalgal communities toward opportunistic species. Unattached seaweed communities dominated by Furcellaria lumbricalis , which have been a resource for hydrocolloid production since the 1940s, have been severely reduced due to eutrophication and unsustainable harvesting and are nowadays only exploited commercially in Estonia. On the other hand, the biomass of opportunistic seaweeds of various red, green and brown algal genera has increased. They cause ecological problems, are a nuisance on many tourist beaches and constitute at the same time a potential bioresource that is so far only exploited to a limited extent for production of energy and fertilizer. Commercial seaweed cultivation is largely focused on Saccharina latissima and still very limited, but is currently being expanded as a compensation measure for sea-based fish aquaculture. Also land-based seaweed cultivation is primarily employed for recycling of nutrients in tank animal aquaculture, but in most cases so far only on an experimental scale.

Poland, a Central European country with a Baltic Sea coastline of 634 km, has no tradition of nearshore cultivation of seaweeds or utilization of this biomass. The Baltic is known for its eutrophication. Numerous attempts are being made to combat this phenomenon as well as to find applications for the beach-cast and free-floating macroalgae, which are a nuisance in many areas. Seaweed harvesting can mitigate eutrophication by the reduction of nutrients – especially nitrogen and phosphorus – in water. Collected biomass can be utilised in agriculture as biofertilisers and used as a valuable raw material for the manufacture of high-value macroalgal products, such as biostimulants of plant growth, feed additives, components of cosmetics, food additives or biogas as a form of renewable energy. The Baltic abounds in green macroalgae ( Ulva sp. and Cladophora sp.) with brown ( Ectocarpus sp., Pilayella sp., Fucus vesiculosus ) and red algae ( Vertebrata sp., Ceramium sp., Furcellaria sp.) occurring in much smaller quantities. These seaweeds are also of great interest as bioindicators of environmental pollution. The seaweeds in the southern Baltic Sea still represent an unexploited biomass and can be a huge source of innovation. New approaches towards macroalgal utilisation are in demand.

In spite of the natural harsh marine environments and continuous global change stressors affecting the Levant basin, the Israeli marine flora in the Eastern Mediterranean Sea is quite diverse, with about 300 recognized species. Such high seaweed biodiversity for a small maritime area is remarkable compared to the ca. 1200 species described for the entire Eastern Mediterranean Sea. Since about the year 1890, the Levant basin has been hosting over 115 seaweeds species that migrated from the Indo-Pacific through the Suez Canal. Indeed, approximately 16% of the marine flora is regarded as invasive or exotic to the Israeli shores, in a process that constantly reshapes seaweed populations and their biodiversity. In spite of significant contributions by Israeli scientists to the general biology and technologies for seaweed cultivation worldwide, Israel has little historical and cultural tradition of commercial seaweed cultivation, or use. At present, only two commercial companies are engaged in land-based seaweed cultivation ( Ulva sp. and Gracilaria sp.) with a number of products marketed locally and abroad. Recently, offshore cultivation and biorefinery approaches have been explored, but not yet commercialized.

A preliminary survey of the economic seaweed exploitation in Madagascar was published in 1998. The present study is an update of the situation after the large scale development of Eucheumatoid cultivation in this country. It represents a floristic survey and it includes more seaweed species than previously described. The economic impact of this new and promising source of income on the local population is also discussed.

Natural seaweed beds, which play an important role for coastal ecosystems and marine fisheries, have been changing drastically in Japan. Interventions, such as decreasing the over-grazing by sea urchins, are being undertaken to maintain natural seaweed beds. Japan has at least 15 seaweed genera of economic importance utilized either directly as human food, as ingredients in food, or as raw materials for extraction of chemical compounds for various applications. Most species are produced through various cultivation methods that usually start in a land-based facility and are completed when seaweeds are transferred for open-sea cultivation. Cultivation, as well as harvesting, from natural populations, has sustained the Japanese seaweed industry for many years, but recently a downfall in seaweed production has been experienced in some areas for certain species due to warming oceans. Efforts to improve production have led to the development of forced cultivation techniques to reduce the cultivation period for Saccharina japonica while hybridization of different morphological forms of Undaria pinnatifida has resulted in the production of so-called “southern” and “northern types” that have desirable shapes for harvesting and processing. The future of the seaweed industry in Japan is geared towards producing high-grade products from seaweeds grown in land-based tanks using deep-ocean water.