Fine-scale spatial patterns in bacterial community composition and function within freshwater ponds

Abstract

The extent to which non-host-associated bacterial communities exhibit small-scale biogeographic patterns in their distribution remains unclear. Our investigation of biogeography in bacterial community composition and function compared samples collected across a smaller spatial scale than most previous studies conducted in freshwater. Using a grid-based sampling design, we abstracted 100 þ samples located between 3.5 and 60 m apart within each of three alpine ponds. For every sample, variability in bacterial community composition was monitored using a DNAfingerprinting methodology (automated ribosomal intergenic spacer analysis) whereas differences in bacterial community function (that is, carbon substrate utilisation patterns) were recorded from Biolog Ecoplates. The exact spatial position and dominant physicochemical conditions (for example, pH and temperature) were simultaneously recorded for each sample location. We assessed spatial differences in bacterial community composition and function within each pond and found that, on average, community composition or function differed significantly when comparing samples located 420 m apart within any pond. Variance partitioning revealed that purely spatial variation accounted for more of the observed variability in both bacterial community composition and function (range: 24-38% and 17-39%) than the combination of purely environmental variation and spatially structured environmental variation (range: 17-32% and 15-20%). Clear spatial patterns in bacterial community composition, but not function were observed within ponds. We therefore suggest that some of the observed variation in bacterial community composition is functionally 'redundant'. We confirm that distinct bacterial communities are present across unexpectedly small spatial scales suggesting that populations separated by distances of 420 m may be dispersal limited, even within the highly continuous environment of lentic water.

Unravelling the drivers of aquatic communities using disparate organismal groups and different taxonomic levels

“…Our results showed that spatial factors may either purely or accompanied with water chemistry play at least a minor role in determining bacterial community structures. As opposed to findings of Lear et al (2014) who stated that lentic bacterial communities in highly connected systems may be limited by dispersal when the distance between sites reaches 20 m, we found no definite signs for dispersal limitation of bacteria in our highly connected study system. By contrast, a large proportion of explained variation in bacterial communities was related to the pure effect of water chemistry, while spatial variables had only small effects on community structure.…”

“…Our results largely support the importance of local environmental conditions as water chemistry variables explained a relatively large proportion of variation in bacterial community structure at the three taxonomic levels we studied. However, there is evidence that spatial processes (Reche et al, 2005;Lear et al, 2014), temporal variation of different assembly mechanisms related to abiotic factors (Langenheder et al, 2012) and the occurrence of a keystone predator (Berga et al, 2015) may also affect bacterial community structures. Our results showed that spatial factors may either purely or accompanied with water chemistry play at least a minor role in determining bacterial community structures.…”

The biogeography of abundant and rare bacterioplankton in the lakes and reservoirs of China

“…Unsurprisingly, most abundant bacteria appeared to be habitat generalists in our study, given that 98% of abundant OTUs occupied 450% of sites. Similarly, Lear et al (2014) found that the regional factors explained the largest proportion of variation of bacterial community composition in the ponds that are connected to each other by ephemeral channels. These authors suggested that large numbers of immigrant taxa are received by each pond that could enhance the connection between community composition and regional factors.…”

“…Recently, Lindström and Langenheder (2012) depicted the relationship between regional and local factors along gradients of dispersal rate and selective strength. It has been suggested that the nature of bacterial communities is important in the creation of wider biogeographical patterns as the dispersal potential could affect the connection between community composition and local and regional factors (Lindström and Langenheder, 2012;Lear et al, 2014). The most abundant bacteria can disperse readily as there are, by definition, many more individuals that can potentially be involved in a dispersal event.…”

Spatiotemporal variation of the bacterioplankton community in the German Bight: from estuarine to offshore regions

“…Hence, unveiling the mechanisms that regulate and maintain this diversity, microbial community assembly, distribution and variation is of fundamental interest in marine ecology. The existence of microbial biogeographic patterns is well established and it has been studied extensively in aquatic systems during the past few decades on various spatial scales [11,22,23,28]. A common understanding is that bacterial community similarity is decreasing with increasing geographic distance referred to as "distance-decay" relationship.…”