Cladophora spp. (Chlorophyta) modulate environment and create a habitat for microalgae in hypersaline waters

Cladophora spp. constantly or periodically form floating and benthic mats in Crimean hypersaline lakes and lagoons. In 2017–2018, characteristics of the Cladophora mats and the microalgae on Cladophora filaments were studied employing field research and microscopy. The whole Cladophora mat has a vertical structure, including the upper and lower layers of the floating mat and benthic mat. In total, 50 species of microalgae were found: 40 of them belonged to Bacillariophyta (Bacillariophyceae and Mediophyceae), two to Haptophyta (Coccolithophyceae), four to Miozoa (Dinophyceae), one to Chlorophyta (Zygnematophyceae) and three to Cyanobacteria (Cyanophyceae). Floating layers of the mat differed significantly in species composition from the benthic mat. The total abundance of microalgae and their biomass on Cladophora (per unit area of filaments) varied widely within sampling sites from 3.79 × 106 to 5.04 × 108 cells m–2 and 2.6 to 2197.8 mg m–2. The total mass of microalgae achieved more than 32% of the mass of Cladophora, averaging 7.7% (standard deviation = 13.3).