A 50-year sediment record of algal assemblage changes in Hanabanilla Reservoir, Cuba

Hanabanilla Reservoir, south-central Cuba, is used for electric power generation, potable water supply and tourism. We examined stratigraphic shifts in algal assemblages that accumulated in the reservoir sediments from the time of construction in 1960 through 2012, and inferred the environmental drivers of such biological changes. Historical fluctuations in algal assemblages were driven by scouring of the reservoir bottom, changing water level, and input of organic matter and nitrogen to the water body. Stage records, in conjunction with algal counts, confirm the importance of the pennate/centric diatom ratio for reconstructing past water-level changes. Although nutrient and organic matter inputs to the reservoir also influenced algal abundance and community composition, our findings suggest that regulating reservoir hydrology could be an effective strategy for preventing future cyanobacterial blooms. Shifts in the relative abundances of algal taxa, and dominance of R strategists associated with extreme fluctuations in water level, showed the strong influence of hydrology as a determinant of primary producer assemblage structure.