  Citation: Michaud, E.; Aschenbroich, A.; Gauthier, O.; Fromard, F.; Aller, J.Y.; Aller, R.C.; Brunier, G.; Anthony, E.J.; Gardel, A.; Le Garrec, V.; et al. The Codevelopment of Mangroves and Infaunal Community Diversity in Response to the Natural Dynamics of Mud Deposition in French Guiana. Sustainability 2022, 14, 2829. https:// doi.org/10.3390/su14052829 Academic Editor: Sharif Ahmed Mukul Received: 10 December 2021 Accepted: 24 February 2022 Published: 28 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). sustainability Article The Codevelopment of Mangroves and Infaunal Community Diversity in Response to the Natural Dynamics of Mud Deposition in French Guiana Emma Michaud 1, * , Adélaïde Aschenbroich 1 , Olivier Gauthier 1 , François Fromard 2 , Josephine Y. Aller 3 , Robert C. Aller 3 , Guillaume Brunier 4 , Edward J. Anthony 4 , Antoine Gardel 5 , Vincent Le Garrec 6 , Aude Leynaert 1 and Gérard Thouzeau 1 1 University Brest, CNRS, IRD, Ifremer, LEMAR, 29280 Plouzané, France; adelaide.aschenbroich@gmail.com (A.A.); olivier.gauthier@univ-brest.fr (O.G.); aude.leynaert@univ-brest.fr (A.L.); gerard.thouzeau@univ-brest.fr (G.T.) 2 Laboratoire Ecologie Fonctionnelle et Environnement, Université de Toulouse, CNRS, INP, 31062 Toulouse, France; francois.fromard@univ-tlse3.fr 3 School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, New York, NY 11794-5000, USA; josephine.aller@stonybrook.edu (J.Y.A.); robert.aller@stonybrook.edu (R.C.A.) 4 Aix-Marseille Université, CNRS, IRD, INRA, Coll France, CEREGE, 13545 Aix-en-Provence, France; guillaume_brunier@hotmail.fr (G.B.); anthony@cerege.fr (E.J.A.) 5 USR LEEISA, 97334 Cayenne, France; antoine.gardel@cnrs.fr 6 University Brest, CNRS, IRD, Observatoire OSU-IUEM, 29280 Plouzané, France; vincent.legarrec@univ-brest.fr * Correspondence: emma.michaud@univ-brest.fr Abstract: The sustainability of mangrove ecosystems requires a knowledge of their spatiotemporal variability as a function of regional properties. The unique coastal ecosystems of the mangrove belt along the coast of the Guianas in South America are influenced by cycles of a massive accretion of mud supplied by the Amazon River and wave induced erosion. This study characterized, for the first time, how benthic infaunal assemblages, as proxies of mechanisms of mangrove resilience, were structured by the natural growth track of Avicennia germinans dominated mangroves in French Guiana. We sampled 4 mobile mud stations and 27 consolidated mud stations distributed over 9 tidal transects from bare to vegetated mudflats colonized by young mangroves during the dry season. We collected a complete dataset of sediment and vegetation variables together with the benthic meso- (>0.25 mm) and macrofauna (>1 mm). We used a combination of eigenvector based multivariate analyses and variance partitioning on this multiple set of variables to identify which environmental variables likely drive the benthic diversity patterns. Mangrove early development increased the alpha and beta diversities of the infaunal communities for the two size classes. A total of 20–30% and 7–12% of the beta diversity are explained by linear and nonlinear spatial variables, respectively. However, 7% to 9% of the variance partioning could be determined by other biotic/abiotic variables, biological interactions or neutral processes, not described here. This study has highlighted the necessity of taking into account mangrove dynamics at suitable spatial scales for benthic biodiversity evaluation and mangrove management or restoration plans. Keywords: intertidal tropical mudflat; mangroves; benthos; alpha and beta diversity; Amazon influence; resilience 1. Introduction Mangroves are one of the most productive ecosystems along subtropical and tropical coastlines. These systems are threatened by a range of anthropogenic pressures, including deforestation, pollution, and urbanization, and by climate changes, including recurrent Sustainability 2022, 14, 2829. https://doi.org/10.3390/su14052829 https://www.mdpi.com/journal/sustainability