Gomphonema baishaensis sp. nov. (Bacillariophyta, Gomphonemataceae), a new diatom species from Guangdong Province, China

This study describes a new species, Gomphonema baishaensis sp. nov., from epilithic samples taken from the Baisha River in the Pearl River Basin. In July 2021, epilithic samples were collected from sunken rocks by scrubbing with a toothbrush. Specimens were analyzed using light (LM) and scanning electron microscopy (SEM), revealing morphological features: heteropolar clavate valves, with the widest region closer to the apex than the central area in larger specimens; uniseriate rows of perpendicular slit-shaped areolae transitioning to biseriate rows near the mantle; uninterrupted striae extending to the mantle; double rows of slit-like areolae near the apices. Key diagnostic traits differentiating it from similar species (G. tamilensis, G. clavatulum, G. spirkovskae, and G. insigniforme) include higher striae density, valve outline, length and width, and areola composition. Environmental factors were measured including pH (8.1), water temperature (32.2 °C), conductivity (225 µS/cm) and dissolved oxygen (DO 7.91 mg/L). These findings increase our understanding of the morphology and distribution of the genus Gomphonema in China.