Jean-Charles Leclerc1,2, Tom Le Gal1, Aurélien Baud1, Eléa Gonthier1,2, Simon Dittami3, François Thomas3, Gwenn Tanguy4, Amandine Nicolle1,5, Marine Moal6, Maéva Gonzalez1, Aurore Raoux7, Romain Crec’hriou6, Caroline Broudin4, Céline Houbin6, Lucie Caradec4, Lucie Blondel4, Erwan Legeay4, Dan Potin4, Stéphane Loisel1, Laure Sevin1, Jérôme Coudret1, Aline Migné1, Dominique Davoult1, Thomas Burel8, Gaëtan Schires4, Jean-Philippe Pezy7, Philippe Potin3, Eric Thiébaut1,6
1Sorbonne Université, CNRS, UMR 7144 AD2M, Station Biologique de Roscoff, France - 2Université de Caen-Normandie, MNHN, SU, UA, CNRS, IRD, UMR 7208 BOREA, Station Marine de Luc sur mer (CREC), France - 3Sorbonne Université, CNRS, Laboratoire de Biologie Intégrative des Modèles Marins, LBI2M, France - 4Sorbonne Université, CNRS, FR2424, Station Biologique de Roscoff, France - 5ENSTA | Institut Polytechnique de Paris, France - 6Sorbonne Université, CNRS, OSU STAMAR UAR2017, Station Biologique de Roscoff, France - 7UNICAEN, Laboratoire Morphodynamique Continentale et Côtière, CNRS UMR 6143 M2C, Université de Normandie, France - 8Univ Brest, CNRS, IRD, Ifremer, LEMAR, F-29280 Plouzané, Brittany, France
Artificial structures are proliferating in urbanized coastal areas, impacting natural habitats. However, there is limited knowledge about the species assemblages they support, ranging from micro- to macro-organisms. As these systems continue to expand, alongside efforts to find sustainable solutions—such as greening grey infrastructures—, there is an increasing need to understand their connectivity, diversity, structure and functioning across seascapes. The project Kelp me! investigated the influence of kelps on these properties, with a particular focus on native kelps both naturally occurring and those seeded along marina pontoons. According to a simulated connectivity model based on passive dispersal of kelp spores, we demonstrate that marinas, unlike recent wind farms, could contribute to the supply of kelp propagules to natural reefs in two ecoregions where kelp populations have declined. Following a field survey across 18 sites of 3 ecoregions, we observed significant covariations between kelp biomass and the communities of invertebrates and fish. Yet, the scales at which these covariations are observed depend on whether the macroalgae are native or aliens. A field experiment conducted at 5 sites further shows that, after 3 and 9 months, the addition of kelp in ports has little to no effect on the fouling diversity, biomass, carbon and nutrient fluxes. The effects were more pronounced in kelp farms. Yet in none of these novel systems any effect of seeded kelp diversity on these properties could be detected. The different kelp species deployed were colonized by similar assemblages of bacteria, flora and fauna – alien dominated-assemblages being generally overwhelming on a short term in ports. We conclude that, although kelps growing naturally can influence diversity and ecosystem functions, there may be little point, if not adverse effects, in attempting to seed these organisms on some artificial habitats without further management of environmental conditions.
Biography
Jean-Charles Leclerc is marine community ecologist, especially interested in biodiversity and ecosystem functioning relations. His recent research has focused on the establishment of such relations within novel communities and their interactions with human activities.