Characterizing seasonal changes in physicochemistry and bacterial community composition in hyporheic sediments

Abstract

The hyporheic zone of stream ecosystems is a critical habitat for microbial communities. However, the factors influencing hyporheic bacterial communities along spatial and seasonal gradients remain poorly understood. We sought to characterize patterns in bacterial community composition among the sediments of a small stream in southern Ontario, Canada. We used sampling cores to collect monthly hyporheic water and sediment microbial communities in 2006 and 2007. We described bacterial communities terminal-restriction fragment length polymorphism (TRFLP) and tested for spatial and seasonal relationships with physicochemical parameters using multivariate statistics. Overall, the hyporheic zone appears to be a DOC, oxygen, and nitrogen sink. Microbial communities were distinct from those at the streambed surface and from soil collected in the adjacent watershed. In the sediments, microbial communities were distinct between the fall, spring, and summer seasons, and bacterial communities were more diverse at streambed surface and near-surface sites compared with deeper sites. Moreover, bacterial communities were similar between consecutive fall seasons despite shifting throughout the year, suggesting recurring community assemblages associated with season and location in the hyporheic zone. Using canonical correspondence analysis, seasonal patterns in microbial community composition and environmental parameters were correlated in the following way: temperature was related to summer communities; DOC (likely from biofilm and allochthonous inputs) influenced most fall communities; and nitrogen associated strongly with winter and spring communities. Our results also suggest that labile DOC entering the hyporheic zone occurred in concert with shifts in the bacterial community. Generally, seasonal patterns in hyporheic physicochemistry and microbial biodiversity remain largely unexplored. Therefore, we highlight the importance of seasonal and spatial resolution when assessing surface-and groundwater interactions in stream ecosystems.

Habitat heterogeneity influences the response of microbial communities to severe low‐flow periods in alluvial wetlands

“…For example, microbial activities increased in the isolated pool sites during the low‐flow period, while they decreased in the running water and upwelling sites, highlighting differences in the environmental characteristics that drive microbial compartmentalisation. As microbial activities were significantly influenced by temperature and TOM, the increase in temperature, and a stable TOM content during the low‐flow period in these stagnant sites, probably stimulated microbial processes (Findlay et al ., ; Febria et al ., ). By contrast, the decrease in activities in the running water and upwelling sites may result from temperature buffering by groundwater inputs, and the progressive decrease in organic content of the sediments.…”

“…Changes in community composition within the sediment led to homogenisation one month after the low‐flow period at a sediment depth of 50 cm. Such seasonal variation in communities within the sediment has already been described (Febria et al ., ; Zhou et al ., ), but our results showed a delayed response (i.e. homogenisation) of microbial communities in the sediment compared with the surface of the wetland.…”

“…However, the impact of partial drying or severe low‐flow periods on microbial processes at the floodplain scale remain largely unexplored, especially in terms of the modalities of water level decrease (linked to the shape of the wetland and its connection with the river and the ground water). Also, changes in microbial processes in the face of hydrological changes have been recently observed to a depth of 100 cm in porous aquifers (Febria et al ., ; Zhou, Kellermann & Griebler, ). At this depth, microbial communities differ from those of the streambed surface (Febria et al ., ).…”

Anthropic effects on the meiofauna and physicochemical characteristics of the hyporheic zone in a Mediterranean stream

“…In general, this community is extremely sensitive to external perturbations, and is categorized as having low resistance (Fowler and Death 2001;Sliva and Williams 2005). In addition, subterranean, lenthic and oligotrophic lotic ecosystems have a long recovery time, that is, low resilience (Stepenuck et al 2002;Febria et al 2009). Thus, these perturbations, principally of anthropic origin, are damaging both to the ecological equilibrium and the autoregenerating capacity of the hyporheic zone, the main link in the process of integral recovery of fluvial ecosystems.…”

Spatial distribution patterns of the hyporheic invertebrate communities in a polluted river in Romania

“…Different authors have emphasized sediments as a significant factor in the interactions between biotic and abiotic elements of surface and interstitial waters (Hendricks & White, 1995;Brunke & Gonser, 1997;Dole-Olivier, 1998). Others highlight the importance of organic matter (Griebler & Mösslacher, 2003;Datry et al, 2005;Hahn & Matzke, 2005), or bacteria (Brown et al, 2003;Griebler & Mösslacher, 2003;Febria et al, 2009) in shaping the biological communities of groundwater and hyporheic zone.…”