Taxonomy and abundance of epibenthic Prorocentrum (Dinophyceae) species from the tropical and subtropical Southwest Atlantic Ocean including a review of their global diversity and distribution

In the tropical and subtropical South Atlantic Ocean, studies on the taxonomy and abundance of benthic harmful algae are scarce and the region has been largely under investigated. In this study, morphological descriptions, molecular (LSU rDNA and ITS region) and abundance data of benthic Prorocentrum species from the tropical and subtropical Southwest Atlantic and three oceanic islands are presented. Moreover, a review of global benthic Prorocentrum species richness and distribution is presented. Eleven benthic Prorocentrum species were found in Brazil. Morphological and molecular data on P. borbonicum, P. hoffmannianum, P. lima species complex and P. rhathymum were provided. Prorocentrum panamense, P. cf. caipirignum, P. cf. concavum, P. cf. norrisianum, P. emarginatum/fukuyoi/sculptile complex and two not identified species were observed using scanning electron and/or light microscopy, and morphological descriptions are presented. Prorocentrum lima species complex was found at all investigated sites, in abundances up to 2 x 104 cells g  1 FW at the Northeast Brazil, while maximum abundance of all the remaining species did not exceed 1 x 103 cells g  1 FW. The Fernando de Noronha archi-pelago can be considered a hotspot of benthic Prorocentrum species diversity, with ten species registered. Data compiled in the literature review shows a clear latitudinal gradient with higher species richness in tropical and subtropical regions relative to temperate areas. It is also evident that there is a bias caused by taxonomic impediment and an uneven sampling effort, with many regions still to be investigated using a combined morphological and molecular effort. Therefore, the current knowledge on the global distribution of benthic Prorocentrum species is likely underestimated.

Automated summary

Taxonomy and abundance of benthic harmful algae in the tropical and subtropical South Atlantic Ocean have been poorly studied and underinvestigated. This study provides morphological descriptions, molecular data, and abundance information of Prorocentrum species from the region. It also includes a review of global Prorocentrum species richness and distribution. The study identified eleven Prorocentrum species in Brazil, with the highest abundance observed in the Northeast region. The Fernando de Noronha archipelago was found to be a hotspot for Prorocentrum species diversity. The findings suggest that the global distribution of benthic Prorocentrum species is likely underestimated due to taxonomic impediment and uneven sampling effort.