Charophyte diversity and their habitat conservation perspectives: insights from vegetation versus sediments survey of a small pond in Serbia

Many charophytes are rare and endangered algae species. All charophyte species significantly contribute to the stability and health of the ecosystems they inhabit. Charophytes survive in their habitats thanks to the longevity of the diaspores (oospores and gyrogonites) in the sediment. Many charophyte species have a specific phenology and can sometimes be overlooked in surveys of macrophyte vegetation. We monitored vegetation for three years and collected sediment from a small water body in Serbia to test the hypotheses that (a) Extant charophyte diaspores have promising, yet currently limited application as taxonomic markers, (b) Vegetation data on charophyte diversity may provide different information than data obtained by extracting diaspores from sediments and (c) parallel surveys of vegetation and sediments can provide a more comprehensive view of charophyte diversity compared to traditional annual vegetation monitoring. Diaspores proved to be promising taxonomic characters for charophyte identification. In our study, six taxa could be identified on a species level based on diaspores alone, while one species group (Chara spp.) requires further investigation as it could consist of up to four species. Compared to vegetation, the sediment survey provided different information on charophyte diversity and confirmed the presence of the species Sphaerochara intricata and Sphaerochara prolifera, which were never detected during the vegetation survey. Sediment studies conducted in parallel with vegetation studies provide important insight into the diversity of charophytes and the prospects for their habitat conservation.