Se presentan los resultados obtenidos en un estudio sobre las algas marinas bentónicas en ocho localidades del litoral de Campeche, México. Se determinó la presencia de 211 taxones de algas marinas, siendo el grupo Rhodophyta el más diverso con 102 taxones, sigue en importancia Chlorophyta con 66 especies, seis variedades y cuatro formas, Heterokontophyta con 19 especies y por último Cyanobacteria con 14. La lista florística se acompaña de datos sobre presencia, estacionalidad, reproducción, nivel de marea y referencias De los 211 taxones, 30 son nuevos registros para Campeche, y se cita por primera vez a Centroceras micracanthum yStreblonema invisibile para la costa occidental del Atlántico de México. Por otro lado, se compara la diversidad específica entre la estación climática de lluvias y la de secas durante 2003, 2004, 2006 y 2007. La ficoflora ubicada en Campeche es de afinidad tropical y la diversidad más grande fue encontrada durante la época seca.

This is the first revision of Neogoniolithon species on the east coast of Mexico based on both DNA sequences (psbA) and morpho-anatomical characters. Nine species names are provisionally applied based on morpho-anatomical comparisons with type specimens or with species descriptions: N. accretum, N. acropetum, N. erosum, N. mamillare, N. propinquum, N. rhizophorae, N. solubile, N. spectabile and N. strictum. For none of these species was type or topotype material sequenced, but all have their type localities in the subtropical or tropical western Atlantic Ocean. Neogoniolithon siankanensis is described on the basis of a distinctive branched thallus, apical tetrasporangial conceptacles and DNA sequence. Another four species are present, each characterized by DNA sequence, but insufficient reproductive material was available to adequately describe these species. A suite of vegetative and reproductive characters can adequately segregate the currently named Mexican east coast Neogoniolithon species, including 1) branched versus unbranched thalli, 2) monomerous versus dimerous construction, 3) disposition of trichocytes, 4) interior dimensions of mature tetrasporangial conceptacles, 5) number of cell layers comprising tetrasporangial conceptacle roof and 6) shape of cells that line tetrasporangial pore canal. Morpho-anatomical descriptions and distributions are provided for all named species.

Seaweeds in the offshore waters of Isla Mujeres, in the western Caribbean Sea on the east coast of the Yucatán peninsula, were sampled using SCUBA. Three species of Cyanophyta, 90 Rhodophyta, 21 Ochrophyta and 41 Chlorophyta were identified. New records and earlier accounts of the shallow-water flora around the island indicate a rich flora of 400 taxa. Five localities around the island were sampled and each had a distinctive community of seaweeds. Over two-thirds (104) of the 155 taxa identified were present at only one of the five localities, and only one species was present in all five localities.

Studies of benthic marine and estuarine algae as well as Cyanobacteria are in their early stages in the littoral of the state of Tabasco. Sixty seven taxa of seaweeds are currently known from Tabasco. The inventory of these organisms was made based on samples obtained in six localities, three of them in marine and three in estuarine environments. We found 147 species and subspecific taxa with Rhodophyta having the greatest number with 84, followed by Chlorophyta 44, and finally Phaeophyceae 19. In addition, the 26 species of Cyanobacteria collected are recorded for the first time for the coast of Tabasco since there are no previous reports. The presence of 115 species of benthic marine and estuarine algae is reported for the first time for Tabasco. Most of the new records are Rhodophyta (53.9%), followed by Chlorophyta (29.5%) and Phaeophyceae (16.6%). Of the 115 new records of algae for Tabasco, Gayliella fimbriata and Grateloupia subpectinata are new records also for the Mexican Atlantic. The highest number of species was recorded for Sanchez Magallanes breakwater, while the lowest number of taxa was recorded for Mecoacan Lagoon. According to the Feldmann and Cheney indexes the algal flora of the coast of Tabasco is tropical. The greatest diversity was found during the rainy season.