Potentially harmful Ostreopsis spp. in the coastal waters of Alexandria - Egypt

Résumé

Ostreopsis spp. has been reported for the first time from the Egyptian Mediterranean waters. Macroalgal samples were collected monthly between June 2005 and December 2007, from the rocks at Abu Qir, from less than 1.5 m depth, and their associated microalgae examined. Populations of two Ostreopsis morphotypes were found to occur in this location, east of Alexandria, viz., O. cf ovata Fukuyo and Ostreopsis morph1. The Ostreopsis spp. was abundant and dominant during the summer. They were more abundant as epiphytes of the brown algae Padina sp. and Sargassum sp., less abundant on the red algae Corallina sp., Jania sp., Laurencia sp. and even less so on the green algae Ulva spp. Ostreopsis cf. ovata was also identified during the summer months on the same macroalgal species, although in a much lower abundance. Ostreopsis spp. alternated in dominance with the benthic cyanobacteria Oscillatoria spp. and the diatom Licmophora sp. Other benthic dinoflagellates recorded at low abundance included Amphidinium carterae, Gymnodinium sp. and Prorocentrum lima.