Planothidium iberense sp. nov., a new brackish diatom of the Ebro Estuary, northeast Spain

This study describes the diatom species Planothidium iberense sp. nov. from a salinity gradient of the Ebro River Estuary in northeastern Spain. A detailed description is given based on light and scanning electron microscopy observations, and the diatom species is compared with morphologically similar Planothidium species. Planothidium iberense is distinguished from P. linkei mainly by its morphometric characteristics, but also by the presence of multiseriate striae, in contrast to biseriate striae in P linkei. Planothidium iberense is also distinguished from P delicatulum and P. septentrionale by the presence of an one-side expanded central area on the sternum valve, which is absent in the latter two Planothidium species.