Over the last century, lakes along the Illinois River have been drained, and levees have disrupted hydrologic connections between the river and its floodplain, resulting in the loss of floodplain ecosystem services.  Recognition of the value of these ecosystem services has encouraged restoration activities, though decades of alternate land use (typically agriculture), have likely altered microbial community composition and activity.  The objective of this study was to characterize and compare microbial communities and the ecological drivers in a newly restored floodplain lake not yet connected to its flood pulse river source (Thompson Lake [TL] area 809 ha; Emiquon Preserve) to an established reference floodplain lake that receives flood pulses (Lake Chautauqua [LC]  area 1416 ha; USFWS).  TL was converted from row crop agriculture in 2007 and is isolated from the Illinois River while LC connects to the river during flood stage.  Lake water was sampled weekly (March-Nov. 2008) and physical (e.g., light, temperature), chemical (TN, TP, pH) and microbiota (Bacteria, Archaea, protozoa, phytoplankton, and zooplankton) data were collected.  Community fingerprinting (i.e., abundance and diversity) of the prokaryotes was assessed by ARISA and light microscopy for protozoa and plankton.  Multivariate analysis approaches (e.g. non-metric multidimensional scaling, correspondence analysis) was used to evaluate spatial and temporal patterns.

Results/Conclusions

The two lakes differed in water quality signatures.   In TL, bottom water decrease in dissolved oxygen (late June) produced an extensive cyanobacterial bloom, likely due to sediment phosphorus release.  In the protist community, ciliate order Oligotrichida dominated in both lakes; testate amoeba were 20X more abundant in CL than TL.  Rotifers and zooplankton where about 5X more abundant in TL than CL while copepod and cladoceran abundances peaked primarily in spring in LC vs. fall in TL.  DNA "fingerprinting" of the bacterial community yielded over 200 bacterial taxa from both lakes and higher diversity in LC; 27 and 59 species were unique to TL and LC respectively.  Conversely, greater diversity of rotifers and autotrophs were found in TL than in LC.  Microbial community change was sequential and directional with time.  Primary ecological drivers in both lakes appeared to be temperature and DOC.  Rapid community changes and identification of unique species opens the door for better understanding of restoration and ecosystem function.  Community changes in TL reflect the early stages of instability that accompany newly restored lakes.  This work increases our understanding of the ecological drivers of microbial communities and processes that underpin environmental quality and sustainability.