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 tax identified were present at only one of the five localities, and only one species was present in all five localities.
Red seaweeds were investigated, using SCUBA, from waters around the island of Cozumel off the east coasat of the Yucatán Peninsula in Mexico. One hundred and eighteen species of Rhodophyta were collected and identified. Forty-five of these are reported for the first time from Cozumel, and of these 11 are new records for Mexico. There was a distinct change in the deep water flora between wet and dry seasons; the dry season had more species with northern ranges in comparison with the flora in general. The wet season had few north-ranging species. Fifty-four epiphytic or hemiepiphytic species were identified, most frequently on Halimeda tuna, Dictyota cervicornis and Sargassum spp. This account brings the total macroalgal taxa reported from Cozumel to 385, the richest flora of any locality in the Caribbean region of Mexico.