Dynamics of phytoplankton succession coupled to species diversity as a system-level tool for study of Microcystis population dynamics in eutrophic lakes

Many of the processes that influence initiation and development of harmful algal blooms (HABs) in lake ecosystems also affect the nature of phytoplankton population overturn-here referred to as the dynamics of succession-and species diversity. Consequently, the dynamics of succession and species diversity might reflect the lake's resistance to HABs. We explored this idea by developing a potential system-level tool based on the coupling of these two characters, where the dynamics of succession were quantified using a first derivative index, and tested it in a single lake plagued by recurrent blooms of Microcystis aeruginosa. Our analysis showed that if nonbloom periods were characteristic of either low succession dynamics or low species diversity, M. aeruginosa blooms followed. However, when succession dynamics and species diversity were both high for an extended period, a M. aeruginosa bloom did not follow. Should this relationship hold true in other lakes and when blooms are not as severe, a coupling of succession dynamics to species diversity might prove useful as a tool to evaluate M. aeruginosa population dynamics at the system level. Data at the species level were needed to elucidate this inverse relationship between M. aeruginosa bloom initiation and the dynamics of succession coupled to species diversity. When species data were grouped into coarse taxonomic categories (i.e., groups discernable using in vivo absorption spectra) the relationship was not detectable.

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