Species of Coscinodiscus (Bacillariophyta) from the Gulf of Mexico, Argentina and Antarctic waters: morphology and distribution

In order to study the morphology and distribution of Coscinodiscus species, a large number of surface water samples from the Argentine continental shelf and Antarctica and fewer from the Gulf of Mexico were examined. The greatest number of samples was obtained during oceanographic cruises aboard the Argentine icebreaker A.R.A. "Almirante Irizar" and A.R.A. "Puerto Deseado", within the framework of ARGAU and GEF-Patagonia projects, respectively. Nine species were described by means of light and electron microscopy. Information on their characteristics has been supplemented with environmental data (temperature and salinity). The nine species analyzed, C. alboranii, C asteromphalus, C. bouvet, C. granii, C. janischii, C. jonesianus, C oculoides, C. radiants and C. wailesii, present valves with loculate areolae, except C alboranii and C. janischii, which have both loculate and poroid areolae in the same valve. The pattern of microlabiate processes, in all species documented, have just one ring of processes on the valve margin, whereas C. wailesii presents two rings. Another morphological difference among the species is the external projection of the macrolabiate processes (less evident in the microlabiate), which characterizes C. jonesianus. In addition, we recorded girdle details of C janischii, which has a wide valvocopula and two copulae, which, as far as we can ascertain, have not been included in previous investigations. Most of the Coscinodiscus species discussed in this study have been reported in wide geographic distribution. C. bouvet and C. oculoides have been found only in Antarctic waters and C. alboranii in warm water regions. Of the nine species studied here, only C. wailesii has been found worldwide as an invasive species that produces harmful events.