The sediment akinete bank links past and future blooms of Nostocales in a shallow lake

Abstract

In this paper we analyzed how well the akinete bank in the sediments from a shallow lake reflected past blooms of planktonic Nostocales (Cyanobacteria), the akinete bank´s potential for reflecting future blooms and whether different nutrient scenarios affect germination and recruitment using a laboratory experiment. Most species found in the plankton were also found in the akinete bank and in the germination experiment. Based on their shape, the most abundant viable akinetes in the sediments potentially corresponded to some of the species forming intense blooms in previous years, and coincided with the most abundant species in a 3-week germination experiment. The effects of nutrients on germination and recruitment were only observed in the early phase of the life cycle (day 7), where nitrogen sufficient conditions enhanced germination, while phosphorus concentration had a positive effect on the number of heterocytes. Combined approaches of morphological analysis and experimental germination seems a good method for assessing the past diversity of Nostocales and allowing predictions of the diversity of potential future blooms in shallow lakes and as a tool for water quality management, especially in water bodies lacking information on previous Cyanobacteria blooms.