The Atimo Vatae Expedition, was the joint effort of the Muséum National d'Histoire Naturelle (MNHN, Paris), the Institut d'Halieutique et des Sciences Marines, University of Toliara (IH.SM), and the Wildlife Conservation Society (WCS) Madagascar Programme. The expedition explored the coastal marine fauna and flora of southern Madagascar, from Androka to Fort Dauphin, from April to June 2010. The Karubenthos Expedition was coordinated by the Parc National de Guadeloupe, along with the Muséum National d ́Histoire Naturelle, the Université des AntillesGuyane, and the Université Pierre et Marie Curie. The aim of this marine expedition was to overcome the lack of knowledge on the algae and more generally on the diversity of benthic organisms. This expedition explored the coastal waters around Guadeloupe during May and December 2012. In both expeditions a comprehensive sampling of the marine benthic algal flora was conducted. Specimens of macroalgae were pressed onto herbarium sheets and subsamples were dehydrated in silica gel for subsequent molecular analyses. Among the collected material, those specimens morphologically identified as halymeniacean taxa have been sequenced for the DNA barcode gene (CO1). Subsequently those recognized as putative new taxa were thoroughly observed to document their vegetative and reproductive anatomical structures. Phylogenetic analyses inferred from additional genetic markers (rbcL, LSU) were also conducted to assess the phylogenetic relationships of the Malagasy and Guadeloupian samples with their worldwide relatives. The first published result was a report of two novel species of the genus Yonagunia from Madagascar, moreover additional new halymeniacean taxa were uncovered and will be formally described.