study of Dinophysiales and Prorocentrales of Atlantic Ocean, Gulf of Guinea, Nigeria

Abstract

This study examined the taxonomy, spatial and seasonal occurrences of the Orders Dinophysiales and Prorocentrales in the Atlantic Ocean, from the Bight of Benin to the Bight of Bonny in Gulf of Guinea Nigeria. Samples were collected from Oceanic stations in ten (10) locations drawn from the eight (8) coastal states of Nigeria. Six (6) species of Dinophysiales and 11 species of Prorocentrales were found. Whereas the Prorocentrales comprised exclusively of Prorocentrum species, Dinophysiales consisted of species of Dinophysis (2), Ornitocercus (2), Plalacroma (1) and Ceratocorys (1). The species exhibited differential spatial and temporal variations. Spatially, the distribution of Dinophysiales was generally relatively scanty, with most widely distributed being D. caudata, while D. rotundata and Amphisolenia schauinslandii were rare, while Prorocentrales had a wider distribution with Prorocentrum gracile and Prorocentrum micans as cosmopolitan species and Prorocentrum aporum, P. balticum, P.compressum P. obtusum, P. scutellum and P. rhathymum as restricted species. In terms of seasonal occurrence, D. caudata (Dinophysiales), P. gracile, P. triestinum and P. micans (Prorocentrales) were found at all seasons- dry-wet, wet, wet-dry and dry while D. rotundatum occurred only in the wet season. P. balticum and P. compressum, occurred only in the wet, dry-wet and dry season respectively. Species that were extremely sparse, both spatially and seasonally, were Phalacroma hastatum, Prorocentrum aporum, P. balticum, P. lima and P. compressum. Global distribution of the identified species is also presented. A total of 47.6% of the collection of species identified in this study are known to be toxic and harmful such as Dinophysis caudata, D. rotundata Prorocentrum micans, P. emaginatum, P. lima. P.redfieldii, P.reticulatum and P. rhathymum.