Botanica Marina 2020; 63(1): 17–41 Review Valérie Stiger-Pouvreau* and Mayalen Zubia Macroalgal diversity for sustainable biotechnological development in French tropical overseas territories https://doi.org/10.1515/bot-2019-0032 Received 12 May, 2019; accepted 17 December, 2019; online first 23 Introduction January, 2020 Macroalgae are key members of marine ecosystems that Abstract: This review focuses on the diversity of French provide ecological functions and further ecosystem ser- tropical overseas macroalgae and their biotechnologi- vices. Currently, 11,017 species of macroalgae are known cal applications. After listing the specific diversity, i.e. on our planet, divided into 1901 Ulvophyceae (green 641 species in French Antilles in the Atlantic Ocean, algae), 7083 red algae, and 2033 Phaeophyceae (brown 560 species in the Indian Ocean, and 1015 species in the algae) (Guiry and Guiry 2019). These numerous species South Pacific Ocean, we present the potential of their are distributed in polar, temperate and tropical areas. In metabolites and their main uses. Among the great diver- this review, we present the diversity and the uses of tropi- sity of metabolites, we focus on carbohydrates, proteins, cal macroalgae living in coral reefs, commonly known as lipids, pigments and secondary metabolites, in particular reef macroalgae, growing in French overseas territories. terpenes and phenolic compounds. The main applications Algae present in the mangrove and brackish ecosystems of reef macroalgae are described in human and animal are not taken into consideration. France, including its consumptions, phycocolloids extraction, production of overseas territories (Figure 1), is the only country with active ingredients for health, cosmetics, agriculture, and coral reefs represented in the three oceans of the world bioremediation. For each application, we list what has (Gardes and Salvat 2008). The reefs and their lagoons been done, or will be done in French tropical overseas cover more than 55,000 km2, on average twice the area territories and point out the challenges faced when using of the surrounding land (Andréfouët 2008). French ter- this chemo-diversity, and problems linked to their exploi- ritories obtained the fourth world ranking for countries tation. Finally, we discuss challenges to develop seaweed with coral reefs, as they are home to 10% of the world’s farming, their uses in carbon sequestration and resil- coral reefs (Andréfouët 2008), spread over many overseas ience to global change, their uses for alternative proteins communities whose local economies depend heavily on together with the production of bioenergy and biomate- this ecosystem. Those French overseas territories sur- rials. As a conclusion, we encourage the research on the rounded by coral reefs are presented on Figure 1 and are chemo-diversity of French reef macroalgae for industrial as follows: (1) in the Atlantic Ocean: Guyana, Martinique, applications as these organisms represent a reservoir of Guadeloupe, Marie-Galante, the Saintes, Désirade, Saint- active ingredients that is still insufficiently explored. Barthélemy and Saint-Martin; (2) in the Indian Ocean: Reunion Island, Mayotte and the Scattered Islands; and Keywords: biotechnological applications; coral reef; (3) in the Pacific Ocean: New Caledonia, French Polyne- diversity; French territories; seaweeds. sia, Wallis and Futuna and Clipperton. Since this covers Atlantic, Indian and Pacific oceans, these islands offer an exceptional diversity to explore (Gardes and Salvat 2008); it also invests France with an international responsibil- ity in the area of conservation. Moreover, 95% of French *Corresponding author: Valérie Stiger-Pouvreau, Université de coral reefs are located in the Pacific Ocean (French Poly- Bretagne Occidentale (UBO), CNRS, IRD, Ifremer, UMR-LEMAR, IUEM, nesia, New Caledonia, Wallis & Futuna, Clipperton), with rue Dumont d’Urville, 29280 Plouzané, France, e-mail: valerie. [email protected] those from New Caledonia declared as a World Heritage Mayalen Zubia: University of French Polynesia, UMR-EIO, BP6570, Site in 1998, and also endowed with the largest lagoon 98702 Faa’a, Tahiti, French Polynesia in the world. For France, this is a worldwide recognition Brought to you by | IFREMER - Bibliotheque La Perouse Authenticated Download Date | 2/3/20 10:56 AM 18 V. Stiger-Pouvreau and M. Zubia: French reef macroalgae and sustainable development Figure 1: Distribution of French tropical overseas coral reef territories. Named and surrounding territories are those studied in this review: four in Pacific Ocean, three in Atlantic Ocean and three in Indian Ocean. Adapted from the website pinterest.com of the originality and importance of its reefs, which rep- always amazed the inhabitants of coastal and inland resent 15,000 km2 of the protected coral ecosystem out regions and constitute an important economic resource of the 40,000 km2 existing in French overseas territories through fishing (Newton et al. 2007) and tourism (Moberg (Payri 2018). The types of islands and reefs, i.e. continen- and Folke 1999) for many territories (Cinner et al. 2009). tal islands with barrier reefs, high islands surrounded by fringing reefs, and atolls, are very diverse (Gardes and Salvat 2008). Coral reefs are scattered over shallow and State of coral reefs in French overseas well-illuminated tropical oceans. They are the refuge territories in relation to global change of thousands of species and the life that develops there takes many forms, hence coral reefs represent environ- Gardes and Salvat (2008) provided some information ments of great biological richness. Coral reef ecosystems relating to the state of health of coral communities in cover less than 0.1% of the oceans but can contain nearly French tropical overseas territories that was divided into one-third of the diversity of some taxa (Bowen et al. 2013). two categories following analysis of information gath- They are therefore a crucial part of our natural heritage ered within the framework of permanent monitoring and the biological diversity of the planet. The productivity networks. Pacific territories (e.g. Clipperton, Polynesia, of coral reefs supports a very rich set of inter-dependent Wallis and Futuna, New Caledonia) and Mayotte, where species. Moreover, it is the main source of food and vital the general state of health of coral reefs appears to have resources for many islands and coastal communities. been maintained in the sites which have had long-term Coral reefs also act as natural breakwaters, which protect monitoring, owing to the reef communities’ good resil- the fertile coastlines of many islands and continental ience and moderate pressure from human activity (Moritz countries from erosion by cyclonic swells (Ferrario et al. et al. 2018). Unfortunately, the French West Indies (e.g. 2014). In addition to their intrinsic ecological value, coral Guadeloupe, Martinique, Saint-Barthélemy and Saint- reefs provide many ecosystem services that are both eco- Martin) and Reunion Island, demonstrate a progressive nomically and culturally important to human populations loss in coral cover to the benefit of algal communities, that depend, directly or indirectly, on them (Moberg and particularly on the outer reef slopes, despite periods of Folke 1999). The beauty and diversity of coral reefs have several years of stability and even recovery. Bellwood Brought to you by | IFREMER - Bibliotheque La Perouse Authenticated Download Date | 2/3/20 10:56 AM V. Stiger-Pouvreau and M. Zubia: French reef macroalgae and sustainable development 19 et al. (2004) demonstrated the different phase-shifts taken loads (Hoegh-Guldberg et al. 2007). In some parts of the by coral reefs following an increase of nutrients together Caribbean, this strategy appeared to work in practice; with an increase of fishing pressure, resulting in algal following high temperature and hurricane disturbances, biomass (macroalgae or turf) on coral reefs. Additionally, coral recovery rates were higher in protected areas where Bellard et al. (2012) argued that the multiple components algal cover was more effectively controlled by herbivores of climate change were anticipated to affect all levels (Mumby and Harborne 2010). However, such control of of biodiversity, from organism to biome levels. Under coral resilience is no longer a priority in many countries such a scenario, macroalgae on coral reefs would not be and direct action to reduce carbon emissions has to be spared. Harley et al. (2012) demonstrated the separate implemented with urgency to ensure the persistence of impacts of global warming and ocean acidification (i.e. coral reefs into the near future (Bruno et al. 2019). decreased pH) on seaweed communities and showed that the physiological responses of seaweeds are still poorly known, with different responses to be expected, depend- Reef macroalgae, taxonomy and diversity ing on region but also on algal communities. Nonethe- less, the combined impacts of simultaneous warming and Seaweeds are photosynthetic, eukaryotic organisms which acidification in a more realistic climate change scenario include green, red and brown macroalgae. “Algae” is a remain poorly understood. Although global warming generic, but not taxonomic term, as members belong to and ocean acidification are difficult to reverse in the near different phylogenetic lineages at the origin of their mor- term, we can manage coral reef resilience by conserving phological, physiological and metabolic diversity (Stengel