Studies of the Laurencia complex based on phylogenetic and DNA barcoding analyses revealed a new species, Laurencia longiramea Cassano, G.N. Santos, J.M.C. Nunes, M.C. Oliveira & M.T. Fujii sp. nov., on the Brazilian coast. The rbcL phylogenetic analysis resolved L. longiramea as sister to Laurencia species from the North Atlantic (L. pyramidalis, L. viridis and L. obtusa) and the Caribbean Sea and Gulf of Mexico (L. intricata), with a divergence of 2.4%–3.7%. Using the DNA barcode COI-5P, L. longiramea was closest to L. pacifica from the United States, with a divergence of 4.2%. The new species has the typical features of the genus Laurencia and is characterised by: sparse branching, axes smaller than 1 mm diameter, often long branchlets, lenticular thickenings always present and abundant, and absence of cortical cells projected near branch apices. Morphologically, L. longiramea is similar to Laurencia filiformis. However, an rbcL sequence of L. filiformis from the type locality (Western Australia) confirmed that they are distinct species, with 4.3% divergence. Examination of Laurencia clavata from Brazil, deposited in the University of São Paulo (SPF) herbarium, were misidentified and corresponded to the new species, L. longiramea. In addition, the rbcL and COI-5P sequences of L. clavata from the type locality (Australia) did not join with L. longiramea. Laurencia clavata formed a well-supported clade with the two species of Coronaphycus. Priority supported the recognition of Corynecladia over Coronaphycus, requiring the new combinations Corynecladia elata (C.Agardh) comb. nov. and Corynecladia nova (Metti) comb. nov. Based on our results, Corynecladia clavata does not occur in the Brazilian marine flora.

Many studies have focused on the taxonomy and phylogeny of the family Galaxauraceae with the use of molecular markers, allied to morphological taxonomy, providing a better understanding of the phylogenetic relationships within the family, as well assisting with the specific delimitation. For the Brazilian coast, Galaxauraceae has few studies with morphological taxonomy, but lack studies with a molecular focus. The diversity of Galaxauraceae was assessed in northeastern Brazil (Bahia state) using rbcL and COI-5P, as well as morpho-anatomical analyses. We report four species from Brazil: Dichotomaria huismanii (the first report for the Brazilian coast), D. obtusata, Galaxaura rugosa, and Tricleocarpa fragilis. Molecular and morphological data supported the establishment of two new species for Galaxauraceae: Tricleocarpa laxa sp. nov. and Dichotomaria viridis sp. nov. Tricleocarpa laxa formed a well-supported clade sister to T. natalensis (South Africa, type locality) and T. cylindrica (Australia) in both rbcL and COI-5P analyses, whereas Dichotomaria viridis, formed a moderate clade sister to D. huismanii. The Brazilian sequences of D. huismanii grouped with sequences from the type locality (Bermuda) showing no intraspecific divergence for rbcL, and very low divergence values for COI-5P. The record of D. huismanii in Brazil expands its geographical distribution to the South Atlantic Ocean. Male plants are described for the first time for this species. Even though our results are restricted to a region of northeastern Brazil (Bahia), they clearly revealed a hidden diversity of Galaxauraceae in Brazil.

Português. O fenômeno conhecido como arribada resulta, principalmente, da turbulência do mar, provocada pela ação das correntes, ventos e marés, que arrancam as algas de seus substratos trazendo-as até a praia. Apesar de serem frequentemente incineradas ou enterradas, estudos verificaram que a retirada desta biomassa arribada é considerada prejudicial, em alguns casos, demonstrando que estudos quali-quantitativos acerca de sua diversidade são imprescindíveis para preservar este recurso e estabelecer parâmetros exploratórios. O presente trabalho tem por objetivo determinar a composição específica e a biomassa das algas arribadas ocorrentes em quatro praias do litoral norte do Estado da Bahia, Brasil. As praias foram visitadas bimensalmente durante as marés baixas de sizígia com o intuito de verificar o fenômeno das arribadas. O material coletado foi encaminhado ao laboratório para posterior identificação e mensuração da biomassa. Foram identificados, 123 táxons específicos distribuídos em 58 gêneros das três divisões: 68 Rhodophyta, 28 Heterokontophyta e 27 Chlorophyta. Os gêneros mais representativos foram Gracilaria (Rhodophyta), com 11 espécies, seguido de Dictyopteris (Heterokontophyta) e Sargassum (Heterokontophyta), com 6 espécies cada. A maioria dos táxons foram pertencentes ao grupo funcional macrófita corticada. A biomassa média das algas arribadas (peso seco), correspondeu a um total de 2269,7 g/m2 em 2007, na praia de Itapuã e 2.269,7 g/m² na praia da Pituba no ano de 2010. O gênero Ulva foi o de biomassa mais expressiva em todas as praias, correspondendo a 100% e 97% do total das arribadas nas praias de Itapoã (2007) e Pituba (2010), respectivamente.English. The phenomenon known as arribada results mainly from the turbulence of the sea, caused by the action of currents, winds and tides, plucking algae from their substrates bringing them to the beach. Although they are often incinerated or buried, studies found that the removal of this biomass is considered harmful, in some cases, demonstrating that qualitative and quantitative studies about diversity are essential to preserve this resource exploration and establish parameters. This study aims to determine the species composition and biomass of arribadas occurring in four beaches of the north coast of the State of Bahia, Brazil. The beaches were visited bimonthly during spring low tides in order to verify the phenomenon of arribada. The collected material was sent to the laboratory for further identification and measurement of biomass. Were identified, 123 species distributed in 58 genera of three divisions: 68 Rhodophyta, 28 Chlorophyta and 27 Heterokontophyta. The most representative were Gracilaria (Rhodophyta), with 11 species, followed by Dictyopteris (Heterokontophyta) and Sargassum (Heterokontophyta), with six species each. Most taxa were belonging to morphotype macrophyte corticated. The average biomass of arribada (dry weight), corresponding to a total of 5765 g/m2 in 2007, the beach Itapuã and 2269.7 g/m² on the beach Pituba in 2010. The genus Ulva biomass was the most significant in all the beaches, corresponding to 100% and 97% of the beaches of Arribadas Itapoã (2007) and Pituba (2010), respectively.

Peyssonneliaceae represents a monophyletic clade of red encrusting algae classified Peyssonneliales. Molecular analyses have been important for revealing unknown diversity in this family, which includes small, cryptic organisms, frequently distinguished solely by discrete anatomical characters. Brazil however, remains virtually unknown. To assess this diversity, phylogenetic and barcoding analyses using rbcL, COI-5P and SSU data, as well as morpho-anatomical analyses were performed. Here we report the first occurrence of two genera on the Brazilian coast: Ramicrusta and Incendia, and describe three new species: Ramicrusta fujiiana sp. nov., Ramicrusta paradoxa sp. nov. and Incendia yoneshigueana sp. nov. Ramicrusta was resolved as a monophyletic clade in the three reconstructed phylogenies, and had congruent topologies. In the rbcL phylogeny, Ramicrusta fujiiana formed a well-supported clade sister to a well-supported clade including R. aranea (Vanuatu, type locality) and R. textilis (Jamaica, type locality). Morphological characters of R. paradoxa are not in agreement with the original description of the genus. Therefore, we present an updated and broader concept of Ramicrusta. Incendia was resolved as a monophyletic clade with full support for rbcL. Incendia yoneshigueana is in a sister relationship with I. glabra (Vanuatu, type locality). This study extends the distributions of Ramicrusta and Incendia, proposes three new species, and confirms the effectiveness of rbcL, COI-5P and SSU in inferring phylogenetic relationships and delimiting species in the Peyssonneliales. The integrative approach established clear taxonomic concepts for the studied genera and species, and identified useful characters for genera delimitation in Peyssonneliaceae.

The Lomentariaceae, previously treated as subfamily Lomentarioideae in the family Champiaceae, is one of the six families currently classified in the Rhodymeniales. Relationships within the family are not well-established, and new genera have been segregated from Lomentaria, a notoriously polyphyletic taxon as currently circumscribed. The lack of access to molecular data of type specimens has limited the taxonomic clarifications within the Lomentariaceae. Using new collections from Brazil, historical collections and data available in GenBank, we generated rbcL and COI-5P phylogenies of the Lomentariaceae, and we used species delimitation methods to assess the species-level diversity among sequences. A nuclear LSU rDNA phylogeny, although less representative in number of taxa, confirmed our findings. Our results recovered Ceratodictyon and Semnocarpa as monophyletic, whereas Lomentaria was polyphyletic. Integrating phylogenetic analyses, analyses of genetic variance, and morphological analyses, we revealed a new species, Ceratodictyon sanctae-crucis sp. nov., collected on the coast of Bahia (northeastern Brazil). Having included a newly generated sequence of the holotype of Lomentaria sinensis, a heterotypic synonym of L. hakodatensis, and a sequence from a sample collected near the type locality of L. hakodatensis, we propose the new genus Yendoa gen. nov. to accommodate this species. Our results support a more phylogenetically coherent taxonomic scheme for the Lomentariaceae, which now includes only monophyletic genera.

Macroalgae provide key ecosystem services, forming habitats such as kelp and fucoid forests, rhodolith beds, and coralline reefs that sustain high biodiversity. However, multiple stressors, including climate change, harmful fishery practices, and pollution and coastal urbanization are driving macroalgal diversity loss and changing species composition and abundance. This study aims to assess macroalgal representativeness, richness and endemism in 16 Marine Protected Areas (MPAs), including four oceanic islands, and test if macroalgal assemblages in MPAs are distributed along a latitudinal gradient (0–29° S) in the Southwest Atlantic. To investigate the processes underlying community patterns, β-diversity was decomposition turnover and nestedness components. The complexity of taxonomic structure was measured by taxonomic distinctness. Overall, the studied MPAs comprised 695 macroalgal taxa, about 69% of Brazilian taxa, and 36% of the endemics. Rhodophyta were dominant (449 species) in most studied areas, except at Trindade and Martim Vaz Archipelago MPA, followed by Chlorophyta (158 species) and Ochrophyta (88 species). Macroalgal species composition in MPAs varied with latitude, and not with area size. They were continuously distributed across northeastern, eastern and southeastern Brazil and oceanic island ecoregions, between Fernando de Noronha (3° S) and São Paulo Litoral Norte (23° S) MPAs. Macroalgal diversity dissimilarity among MPAs was 92%, dominated by the turnover component (88%) and nestedness as a minor component (4%), indicating that dissimilarities are mainly driven by the replacement of species, rather than a gradual loss or gain of species. Effective protection of these MPAs should be prioritized as they harbor highly diverse, unique, and heterogeneous macroalgal assemblages along the SWA, surrounded by heavily impacted areas. Assessment of human impacts on macroalgal habitats in MPAs would contribute to defining effective management actions. Mid- and offshore shelf macroalgal habitats, particularly rhodolith beds, which harbor rare kelp species and mesophotic reefs, remain underprotected, and should be integrated into marine spatial planning for biodiversity conservation.