Disentangling multi‐scale environmental effects on stream microbial communities

Abstract

Aim Climate change and anthropogenic environmental deterioration strongly affect aquatic microbial communities. Although microbes have irreplaceable roles in various ecosystems, the spatial variation in microbial communities has received less attention in comparison to macro‐organisms. Studies aiming to disentangle the effects of local environmental, catchment and climatic variables on microbial communities are also rare. Here, we disentangled the effects of local, catchment, spatial and climatic variables on boreal stream diatom and bacterial communities. Location Western Finland Methods We sampled 21 boreal river basins comprising 105 study sites spanning 520 km in north‐south direction and 330 km in east‐west direction in western Finland. We used principal coordinates of neighbour matrix analysis (PCNM), redundancy analyses (RDA), variation partitioning, boosted regression trees (BRT) and regression analyses to examine variation in community composition and species richness. Results Water chemistry and physical variables had significant effects on the community composition of both microbial groups. Catchment level variables explained a slightly larger amount of variation in diatom community composition than local level variables. Agriculture was the most significant determinant of variation in diatom community composition among catchment level variables and was also related with variation in the richness of both groups. Of spatial and climatic variables, growing degree days (GDD) and spatial variables were the most significant drivers determining diatom community composition. GDD was also positively associated with the richness of diatoms and bacteria. Unique effects of spatial and climate variables accounted for the largest amount of variation in the community composition of both diatoms and bacteria. Main conclusions Our results highlight that aquatic microbial communities can exhibit biogeographical variation at regional scales due to the joint influence of local, catchment and climatic variables, and possibly because of dispersal limitation. Catchment properties, especially agriculture, can be used as a proxy for the effects of landscape alteration on aquatic microbial communities.

Local environment and space drive multiple facets of stream macroinvertebrate beta diversity

“…This study was based on a dataset collected from 105 stream sites located in western Finland, reaching a spatial extent of 520 km in the north–south and 330 km in the east–west direction (Figure ). These streams belonged to 21 major river basins draining into the Baltic Sea, mainly into the Gulf of Bothnia, and covered a wide variation in land use, ranging from almost pristine to agricultural landscapes (Jyrkänkallio‐Mikkola et al., ). These streams are located within three climatic‐vegetation zones (i.e., hemiboreal, south boreal, and middle boreal) in Finland (Ahti, Hämet‐Ahti, & Jalas, ; Tapio & Heikkilä, ).…”

“…Stream biodiversity patterns are structured by factors prevailing at multiple spatial scales (Heino, Mykrä, Kotanen, & Muotka, ; Johnson, Goedkoop, & Sandin, ; Townsend et al., ), but surprisingly few studies have concurrently studied the importance of local environmental, catchment and climatic factors in shaping biodiversity patterns (Jyrkänkallio‐Mikkola et al., ; Sandin & Johnson, ). To the best of our knowledge, no study has focused on biodiversity patterns considering species, traits, and phylogenetic facets in this multi‐scale environmental context.…”

Characteristics, Main Impacts, and Stewardship of Natural and Artificial Freshwater Environments: Consequences for Biodiversity Conservation

“…Northern freshwater ecosystems are inhabited by a wide variety of organism groups, including bacteria, algae, macrophytes, invertebrates, fish ( Figure 1W), and waterfowl ( Figure 1V), which show considerable biodiversity at regional and local scales (e.g., [418]). However, there are considerable differences in the levels of biodiversity among organismal groups, and while fish may show generally low numbers of species at regional and local levels in high latitudes (e.g., [419]), bacteria (e.g., [420]), algae (e.g., [421]), macrophytes [422], and invertebrates [423] may exhibit surprisingly high biodiversity considering the constraints set by historical, geographical and climatic factors. Historical factors related to the effects of last glacial maximum resulted in the elimination and subsequent recolonization of biota after the ice age over most of the northern areas (e.g., [416]).…”

Are drivers of microbial diatom distributions context dependent in human‐impacted and pristine environments?

“…, Jyrkänkallio‐Mikkola et al. ). This indicates that land use could provide a more robust measure of water chemistry variables, thus, reflecting stream chemistry at longer time scales than snapshot water samples.…”

“…The relationship between land use and microbial stream communities strengthens toward downstream because of the continuous accumulation of substances in a river continuum (Tudesque et al 2014). Moreover, in some circumstances, stream microbes may show a stronger relationship with the changes in land use than with physicochemical gradients, for example, pH, substrates, and nutrients (Liu et al 2016, Jyrk€ ankallio-Mikkola et al 2017. This indicates that land use could provide a more robust measure of water chemistry variables, thus, reflecting stream chemistry at longer time scales than snapshot water samples.…”