Seasonal changes in microbial community structure and activity imply winter production is linked to summer hypoxia in a large lake

Abstract

Carbon and nutrient cycles in large temperate lakes such as Lake Erie are primarily driven by phototrophic and heterotrophic microorganisms, although our understanding of these is often constrained to late spring through summer due to logistical constraints. During periods of > 90% ice cover in February of 2008, 2009, and 2010, we collected samples from an icebreaker for an examination of bacterial production as well as microbial community structure. In comparison with summer months (August 2002 and 2010), we tested hypotheses concerning seasonal changes in microbial community diversity and production. Bacterial production estimates were c. 2 orders of magnitude higher (volume normalized) in summer relative to winter. Our observations further demonstrate that the microbial community, including single-celled phototrophs, varied in composition between August and February. Sediment traps deployed and collected over a 3 year period (2008-2011) confirmed that carbon export was ongoing and not limiting winter production. The results support the notion that active primary producers in winter months export carbon to the sediments that is not consumed until the warmer seasons. The establishment of this linkage is a critical observation in efforts to understand the extent and severity of annual summertime formations of a zone of regional hypoxia in Lake Erie.

Bacterial community structure and function shift along a successional series of tidal flats in the Yellow River Delta

“…The lowest bacterial phylogenetic diversity in winter in tidal flats is similar to the findings on bacterial communities in coastal water25 and lake sediments26. The decrease of bacterial phylogenetic diversity in low temperature was likely because bacteria are in an inferior position in competition with fungi when the temperature is low27.…”

“…The decrease of bacterial phylogenetic diversity in low temperature was likely because bacteria are in an inferior position in competition with fungi when the temperature is low27. Moreover, rare bacterial taxa are difficult to be detected with limited sequencing depth by virtue of the low biomass of bacteria in low temperature526.…”

“…Seasonal changes in temperature can be directly reflected in bacterial community diversity and function5. For example, microbial community diversity and structure in lake sediments varied between winter and summer in Lake Erie26. Nitrite is involved in nitrification and de-nitrification processes, which are the primary transformation route in wetlands, especially in wetlands with alternating anaerobic and aerobic conditions3233.…”

Microbial communities reflect temporal changes in cyanobacterial composition in a shallow ephemeral freshwater lake

“…To the best of our knowledge, this study represents one of only a few studies to examine the total bacterial population of a freshwater lake on the Australian continent (Dennis et al, 2013) and the first Australian study to do so in the context of a multi-site time series comparable to those conducted elsewhere (Allgaier and Grossart, 2006;Wu et al, 2007; Tang et al, 2010;Dziallas and Grossart, 2011;Eckert et al, 2012;Paver et al, 2013;Wilhelm et al, 2014). During periods of low cyanobacterial biovolume, the microbial community present within the surface water was dominated by the taxa acI (-A and B) (Figure 4a) and alfV-A (Figure 4c).…”

“…Across the bloom period, the rapid accumulation of high levels of organic matter contributes to numerous changes to chemical properties of the water column. Periods of elevated cyanobacterial biovolume can result in oxygenation, nitrification, phosphorus loading of sediments and toxin production, followed by hypoxia owing to mass cell death Wilhelm et al, 2014). In addition, the natural or induced dispersion of cyanobacterial blooms poses a secondary detriment to the quality of water resources through the release of toxic secondary metabolites, collectively termed cyanotoxins (Carmichael, 2001;Ibelings and Chorus, 2007;Funari and Testai, 2008).…”