Connectivity of bacterial assemblages along the Loa River in the Atacama Desert, Chile

Abstract

The Loa River is the only perennial artery that crosses the Atacama Desert in northern Chile. It plays an important role in the ecological and economic development of the most water-stressed region, revealing the impact of the mining industry, which exacerbate regional water shortages for many organisms and ecological processes. Despite this, the river system has remained understudied. To our knowledge, this study provides the first effort to attempt to compare the microbial communities at spatial scale along the Loa River, as well as investigate the physicochemical factors that could modulate this important biological component that still remains largely unexplored. The analysis of the spatial bacterial distribution and their interconnections in the water column and sediment samples from eight sites located in three sections along the river catchment (upper, middle and lower) was conducted using 16S rRNA gene-based Illumina MiSeq sequencing. Among a total of 543 ASVs identified at the family level, over 40.5% were cosmopolitan in the river and distributed within a preference pattern by the sediment substrate with 162 unique ASVs, while only 87 were specific to the column water. Bacterial diversity gradually decreased from the headwaters, where the upper section had the largest number of unique families. Distinct groupings of bacterial communities often associated with anthropogenic disturbance, including Burkholderiaceae and Flavobacteriaceae families were predominant in the less-impacted upstream section. Members of the Arcobacteraceae and Marinomonadaceae were prominent in the agriculturally and mining-impacted middle sector while Rhodobacteraceae and Coxiellaceae were most abundant families in downstream sites. Such shifts in the community structure were also related to the influence of salinity, chlorophyll, dissolved oxygen and redox potential. Network analyses corroborated the strong connectivity and modular structure of bacterial communities across this desert river, shedding light on taxonomic relatedness of co-occurring species and highlighting the need for planning the integral conservation of this basin.

Local and global chemical shaping of bacterial communities by redox potential

“…In addition, multiple lake and ocean datasets are characterized by higher Eh7 for overlying water than sediment (Han et al, 2019;von Hoyningen-Huene et al, 2019;Vavourakis et al, 2019;Molina et al, 2021); most of these exhibit negative correlations with Z C , except for Honghu Lake (Han et al, 2019), which shows a relatively high Z C for water. A systematic difference in redox potential between water and sediment is not evident for river datasets (Cai et al, 2019;Zárate et al, 2020).…”

“…The datasets with negative correlations represent marine (Sánchez-Soto Jiménez et al, 2018;Molina et al, 2021;Wu et al, 2021), coastal (Zhou et al, 2017), freshwater (Zárate et al, 2020;von Hoyningen-Huene et al, 2019), and hypersaline sediments (Vavourakis et al, 2019). The dataset with the most negative fitted slope is that for Daya Bay, China (Wu et al, 2021), where samples were collected from the surface, middle, and bottom of sediment cores.…”

Spatial co-occurrence patterns of benthic microbial assemblage in response to trace metals in the Atacama Desert Coastline

“…This improves efficiency in transferring information, energy, and resources of microbial communities, regard to sediment nutrient conversion and pollutant biodegradation ( Santolini and Barabási, 2018 ; Philippot et al, 2021 ). One explanation for the high spatial connectivity and the selection of the microbe pool in the coastal area surrounding the OL may also be attributed to the Loa River, which acts as a true green/life corridor that runs across the hyper-arid core of the Atacama Desert also known as the dry limit for life on Earth, helping to establish specific networks ( Zárate et al, 2020 ). In this way, the input may support a distinct set of microbial processes that remain unstudied ( Fortunato et al, 2012 ; Fazi et al, 2020 ; Jroundi et al, 2020 ).…”

“…Correlation-based network analysis provides a good way to determine the potential interplays between microbes as well as their structuring and mediating ecological functions in various environments ( Chaffron et al, 2010 ; Banerjee et al, 2018 ; Felipe-Lucia et al, 2020 ), including the Mejillones Bay and Loa River ( Zárate et al, 2020 , 2021 ). Therefore, the results of the present study highlights important targets to better understand microbial responses to the bioavailability of TMs in low-oxygen sedimentary environments.…”

Planktonic and epilithic prokaryota community compositions in a large temperate river reflect climate change related seasonal shifts

“…River microbiota is mostly studied in water or, less frequently, from sediment and very little is known about epilithon. Differences in microbial community structure in the two former habitats have been reported from the Yellow River estuary [ 28 ], the Ibrahim River, Lebanon [ 26 ], the sub-arctic Pasvik River, Norway [ 16 ], and from the Loa River, Atacama Desert, Chile [ 43 ], suggesting that type of river habitat is a key driver in community composition, regardless of climatic conditions. Our study demonstrated strong separation of water and epilithon communities in different Danube sections.…”