Toxic cyanobacteria blooms of Mukhor Bay (Lake Baikal, Russia) during a period of intensive anthropogenic pressure

The status of Lake Baikal as a UNESCO World Heritage Site, due to its unique ecology and value as a global aquatic resource have resulted in strict environmental regulations to protect the watershed and biota it supports. Despite this, the ecosystem of the lake is being exposed to negative anthropogenic impact and deteriorating water quality. In this article, we describe the bioecological state of Mukhor Bay – the warmest bay of Lake Baikal and one which is actively visited by tourists. We try to highlight the environmental problems of Baikal and aim to change attitudes towards water resources in this unique ecosystem. We present data on the taxonomic, genetic, and biochemical characteristics of cyanobacteria blooms that develop in the plankton of the bay. Further, we establishing their risk to human health and provide information for the environmental state management. Toxic blooms of Dolichospermum lemmermannii (cyanobacteria) were detected in the phytoplankton of Mukhor Bay. The nutrients content and chlorophyll concentration was low and corresponded to the oligo-mesotrophic status. Microcystins were detected in the dried phytoplankton biomass and the water, coastal samples contained a higher amount of this toxin. We hypothesize that one of the factors contributing to toxic cyanobacteria growth in the Mukhor Bay is the nutrient loadings due to surface and groundwater runoff from surrounding area.