In the right place, at the right time: the integration of bacteria into the Plankton Ecology Group model

Abstract

Background Planktonic microbial communities have critical impacts on the pelagic food web and water quality status in freshwater ecosystems, yet no general model of bacterial community assembly linked to higher trophic levels and hydrodynamics has been assessed. In this study, we utilized a 2-year survey of planktonic communities from bacteria to zooplankton in three freshwater reservoirs to investigate their spatiotemporal dynamics. Results We observed site-specific occurrence and microdiversification of bacteria in lacustrine and riverine environments, as well as in deep hypolimnia. Moreover, we determined recurrent bacterial seasonal patterns driven by both biotic and abiotic conditions, which could be integrated into the well-known Plankton Ecology Group (PEG) model describing primarily the seasonalities of larger plankton groups. Importantly, bacteria with different ecological potentials showed finely coordinated successions affiliated with four seasonal phases, including the spring bloom dominated by fast-growing opportunists, the clear-water phase associated with oligotrophic ultramicrobacteria, the summer phase characterized by phytoplankton bloom-associated bacteria, and the fall/winter phase driven by decay-specialists. Conclusions Our findings elucidate the major principles driving the spatiotemporal microbial community distribution in freshwater ecosystems. We suggest an extension to the original PEG model by integrating new findings on recurrent bacterial seasonal trends.

Winners in good times and bad times: Aerobic anoxygenic phototrophic bacteria profit from photoheterotrophy under carbon-rich and poor conditions

“…This result contradicts the initial hypotheses (Kolber et al, 2001), but agrees with the fact that many freshwater AAP genera (e.g. Limnohabitans) are considered copiotrophs (Chiriac et al, 2023, Park et al, 2023. Furthermore, in June AAP bacteria grew faster than the heterotrophic bacteria in all treatments, providing experimental support for the recently suggested inclusion of AAP bacteria in the Phytoplankton Ecology Group (PEG) model as super competitors profiting from spring phytoplankton bloom (Villena-Alemany et al, 2023b).…”

Mixing‐driven changes in distributions and abundances of planktonic microorganisms in a large, oligotrophic lake

“…The community of microorganisms in Flathead Lake are similar to those described in other relatively deep and low nutrient aquatic systems, including predominance of putative oligotrophic taxa that exhibit seasonally dependent vertical structure (Park et al 2023). Although absolute abundances of non-pigmented planktonic microorganisms were relatively constant with depth and time, both relative abundances of specific taxa and community diversity varied seasonally and vertically.…”

“…For planktonic microorganisms in temperate lakes, much of the attention has focused on productivity, biomass, and community composition during the high light, stratified season (e.g., Hiorns et al 1997;Oh et al 2011;Skopina et al 2015), with comparatively fewer studies investigating how distributions and abundances of microorganisms change over the year (but see, e.g., Garcia et al 2013;Okazaki and Nakano 2016;Park et al 2023). It remains unclear how changes in lake thermal structure might impact the phenology of planktonic microorganisms.…”

Phenology and ecological role of Aerobic Anoxygenic Phototrophs in fresh waters

“…The annually recurrent phenomena in freshwater lakes include a spring phytoplankton bloom followed by a zooplankton-induced clear-water phase in early summer, a late-summer phytoplankton bloom and a period of low productivity in winter. Recently, seasonal dynamics of heterotrophic bacteria have been incorporated into the model [5], as they rapidly respond to the transitions in the lakes’ pelagic functioning, especially during the phytoplankton bloom [3, 5, 81]. Whilst AAP bacteria have been shown to substantially contribute to the bacterial abundance, biomass and activity in freshwater lakes [13, 17], they are not considered in the PEG model [1, 2].…”