Annual cycle of epiphytic dinoflagellates on theژat Dzi lam de Bravo, Yucatan Peninsula, southeas tern Gulf of Mexico

Epibenthic dinoflagellates are primary producers and also produce toxins that directly or indirectly affect marine coastal ecosyst ems and human health. The objective was to stud y the annual dynamics (May 2012 - May 20 13) of species composition and cell abundance on the seagrass Thalassiatestudinum blades (s ubstrate) of 30-45 cm length, divided equally into basal, medium and apical parts. Monthly sam ples (42 in total) were taken along a 100-m transect (5, 25, 50, 75 and 100 m from the coast) at Dzilam de Bravo (21o23.561´N, 88o53.775´W), the northern coast of Yucatan Peninsula, and fixed in 4% formalin. After a devastating pelag ic microalgal bloom in 2011-2012 that lasted about 150 days, submerged aquatic vegetatio n disappeared from 5 to 70 m, so only the samples taken at 75 and 100 m always contained seagrasses. Site depth was 0.5-1.3 m. Water temperature ranged from 22.3 to 36.5oC and salinity from 29.6 to 37.25. Epiphytes were se parated manually using a microscope slide in a sha llow tray and vigorously agitated for one mi nute in a plastic 500-ml flask; 15-ml aliquots wer e taken for analysis. Cell counting was perform ed in a 1-ml Sedgwick-Rafter chamber using an inverted microscope. Seventeen species from ni ne genera were found: Amphidinium (1), Blixaea (1), Bysmatrum (1), Cabra (1), Coolia (1), Gambierdiscus (1), Ostreopsis (1), Prorocentrum (8), Plagiodinium (1) and Sinophysis (1). T he highest abundances were observed on the apic al parts in the hot rainy season (July-September; up to 3841 cells/g substrate wet weight), lower abundances in the dry season (April; 2584 cells/g) and the lowest on the basal parts in January and February (400 cells/g). It was conc luded that the older blade parts carry more epiphy tic dinoflagellate cells. Prorocentrumlima(potentially toxic), P. cf. sipadanense and Blixae aquin quecorne (benthic-planktonic) were th e dominant species.

Epibenthic dinoflagellates are primary producers and also produce toxins that directly or indirectly affect marine coastal ecosyst ems and human health. The objective was to stud y the annual dynamics (May 2012 - May 20 13) of species composition and cell abundance on the seagrass Thalassiatestudinum blades (s ubstrate) of 30-45 cm length, divided equally into basal, medium and apical parts. Monthly sam ples (42 in total) were taken along a 100-m transect (5, 25, 50, 75 and 100 m from the coast) at Dzilam de Bravo (21o23.561´N, 88o53.775´W), the northern coast of Yucatan Peninsula, and fixed in 4% formalin. After a devastating pelag ic microalgal bloom in 2011-2012 that lasted about 150 days, submerged aquatic vegetatio n disappeared from 5 to 70 m, so only the samples taken at 75 and 100 m always contained seagrasses. Site depth was 0.5-1.3 m. Water temperature ranged from 22.3 to 36.5oC and salinity from 29.6 to 37.25. Epiphytes were se parated manually using a microscope slide in a sha llow tray and vigorously agitated for one mi nute in a plastic 500-ml flask; 15-ml aliquots wer e taken for analysis. Cell counting was perform ed in a 1-ml Sedgwick-Rafter chamber using an inverted microscope. Seventeen species from ni ne genera were found: Amphidinium (1), Blixaea (1), Bysmatrum (1), Cabra (1), Coolia (1), Gambierdiscus (1), Ostreopsis (1), Prorocentrum (8), Plagiodinium (1) and Sinophysis (1). T he highest abundances were observed on the apic al parts in the hot rainy season (July-September; up to 3841 cells/g substrate wet weight), lower abundances in the dry season (April; 2584 cells/g) and the lowest on the basal parts in January and February (400 cells/g). It was conc luded that the older blade parts carry more epiphy tic dinoflagellate cells. Prorocentrumlima(potentially toxic), P. cf. sipadanense and Blixae aquin quecorne (benthic-planktonic) were th e dominant species.