Variation in the abundance of pico, nano, and microplankton in Lake Michigan: Historic and basin-wide comparisons

摘要: Abstract The Lake Michigan ecosystem has undergone numerous, systemic changes (reduced nutrient, changing climate, invasive mussels) that have altered portions of the food web and thus, appear to changed lake's trophic state. That said, little is known about components microbial (MFW, heterotrophic phototrophic pico, nano, micro-plankton), which we hypothesized compensated as a source for crustacean zooplankton given recent declines in biomass large phytoplankton (mainly diatoms). Therefore, measured abundance entire MFW using complementary microscopic techniques, flow cytometry, size fractionated chlorophyll concentrations at sites northern southern Michigan, one site Superior; latter served benchmark oligotrophic conditions. In addition, historic comparison was made between 1987 2013 site. Ppico numbers (i.e., picocyanobacteria) were lower compared with those 1980s; however, percent contribution  50% total chlorophyll). small, pigmented chrysomonads cryptomonads (Pnano category) not significantly different same time Pmicro did decline; this shift towards Pnano dominance may be related oligotrophication Michigan. ciliated protists (Hmicro class) 3-fold levels 1987, while both Hpico (eubacteria, range 0.24–1.36 × 10 6  cells mL − 1 ) Hnano colorless chrysomonads; 0.11–6.4 × 10 3 remained stable reflected resilience bacteria–flagellate linkage.