Observation of novel Didymo-like diatom mats in the Kamenica River (Serbia, Southeastern Europe)

Abstract

Apart from the widespread species Didymosphenia geminata, known for its nuisance mat formation, diatoms that form similar potentially harmful mats are rarely found, especially in Europe. This study presents the first record of thick, mucilage Didymo-like mats dominated by Cymbella affinis (May 2022) and Cymbella perparva (October 2022), in Serbia (Kamenica River). Thin Gomphonella olivacea (February 2022) mats of different appearance were also detected. A lower diatom species diversity (Shannon–Wiener index, Evenness, Simpson's index) was observed in the mats compared to the biofilm on the remaining substrate. Our findings emphasize the need for further research on native, mat-forming diatoms and their ecological impact.