Cerro Tocorpuri, belongs to the II region of Chile, in San Pedro de Atacama, on the border of Chile-Bolivia. The presence of a more or less constant supply of water conditions the existence of characteristic vegetation systems known as bogs (bofedales, vegas and marshes). These wetlands have a cultural, environmental and economic social importance. As a result of the exploitation of aquatic rights, peatlands began to dry up with the consequent loss of natural resources and damage to ancestral rights, and natural resources. The activities of microorganisms in wetlands play an important role in biogeochemical processes. The interaction between microbial diversity and soil, influences to the ability of the ecosystem to recover from stress (resilience). In the present work, the soil characteristics and the associated microbial biodiversity were studied, comparing samples of active and deteriorated peatland. It was seen that the loss of water causes great changes in the physical-chemical characteristics of the soil, which leads to a modification of the microbiota Proteobacteria decreased by 18% in deteriorated peatlands, which are evident more sensible to extreme conditions while Acidobacteria, Actinobacteria increased in these sample showing a better adaptation to the change of conditions. In view of the fact that high Andean Peatlands are exposed to increasing environmental impact, this preliminary comparative study of pristine and altered soil could guide the research directed to recovery of dead peatlands strategies.
The Atacama Desert is the driest and oldest desert on Earth. Its surface conditions have remained relatively unchanged for millions of years [
Cerro Tocorpuri, which belongs to the II region of Chile, is located at 5200 m a.s.l., in San Pedro de Atacama, on the border of Chile-Bolivia. Its coordinates are 22˚25'60"S and 67˚55'0"W in DMS (Degrees Minutes Seconds).
In regions I and II of Chile, the presence of a more or less constant supply of water, conditions the existence of typical vegetation systems known as peatland (bofedales, vegas and bogs), which technically belong to a humid environment [
The vegetation types correspond to biological ecological systems azonal, with characteristic vegetation due to the high and permanent soil moisture content [
The microbial processes in wetland are regulated for the hydrology [
It is known that the soil is a complex habitat with a large number of microbial populations [
Although the interaction between the biodiversity and its function in the soil is not well studied, it is thought that has a positive influence on stability, productivity and resilience towards stress and disturbance [
Peatland degradation was associated with the changes occurred in the regional precipitation, the high water demand for lowland agriculture, urbanization and mining, all of them exceeding the availability of water [
The objective of this work was to study the soil characteristics and microbial biodiversity of soils associated to rhizosphere of wetlands, comparing a “deteriorated peatland (dead peatland)” with a “peatland in good condition (active peatland)”. The results would able to determine which are the essential biotic components in the rhizosphere in order to implement a recovery technology.
Samples were taken in July 2015, from Tocorpuri Peatland, a place located in Second Region, Antofagasta, Chile.
Soils samples in different stages of preservation were collected, deteriorated soil (dead peatland) and soil in good condition (active peatland), as shown in
Total genomic DNA was isolated using the Power Biofilm DNA Isolation Kit (MO BIO Laboratories, inc.) according to the supplied protocol. Extracted DNA samples were amplified with F357 and R926 primers (NIH HMP Working Group, 2009). The reactions were performing according [
The determination of organic material (OM), C (%), Nitrates (%), P (ppm), S
(%) was carried out by standard methods in pH7 diagnóstico agrícola.
To calculate the % moisture for each sample, 10 g of the material was weighed into petri plate (pre-weighed), and the sample was dried for 24 hs in a 100˚C oven (to constant weight). The moisture content was calculated using the following equation:
W= [(PP + wS) - (PP + DS)/(PP + DS) - PP] * 100
W: % moisture; PP: Petri Plate; wS: wet Sample; DS: Dry sample.
The samples processed as described by [
Ten grams of active and dead peatland samples were suspended in 90 ml of peptone water (bacteriological peptone, 0.1%) and vortexed thoroughly for 10 min. From these stock solutions, serial dilutions were performed and plated in duplicated on each culture media: total counts on Agar nutritive incubated for 48 h at 30˚C. On the other hand, BG11 medium [
Many times result difficult to separate soil functions into chemical, physical, and biological processes due of the dynamic nature of these processes. Chemical properties of numerous soil directly influence microbiological processes, and these, together with physical-chemical processes determine, the capacity to hold, supply, and cycle nutrients and on the other hand, the movement and availability of water [
Comparative physical chemical analysis between both samples showed a clear evidence of a higher percentage of moisture present in active peatland (92%) compared with dead peatland (47%). Soil pH is an important factor that affects directly the availability of nutrients and the chemical characteristics of the environment. The microorganisms have optimal pH ranges for their growth, when altered in the environment; significantly modify microbial density [
The conductivity measurements show that in active and dead peatland, they have low conductivity values (0.25 dS/m and 0.28 dS/m respectively). The electrical conductivity was used to classify the samples as slightly saline soils because the values obtained in both cases were among 0 - 0.2 dS/m. As shown in
Nitrogen is an important, growth-limiting nutrient in many peatlands [
The microbiological state of the soil is a critical element in the studies of microbial ecology. The total viable counts on agar nutritive showed differences between analyzed samples. The number of cultivable microorganisms was higher in active peatland 8.89 ± 0.18 log CFU ml−1 compared with 6.85 ± 0.3 log CFU ml−1 in dead peatland.
The soil is considered ecologically habitat extremely stable [
Dead peatland | Active peatland | |
---|---|---|
Organic material (%) | 3.78 | 29.18 |
C (%) | 1.89 | 14.59 |
N-NO3 total (%) | 24.30 | 260 |
P (ppm) | 17.80 | 21.10 |
S (ppm) | 150 | 502 |
environmental conditions are altered. In the case of “dead peatland” samples, water is the main factor that affects the structure of microbial communities, affected mainly by human activity. To elucidate differences in microbial community structure between wet and dry soils, pyrosequencing was undertaken. The results obtained reveal that the most of the 16 S rRNA gene sequences were affiliated with Proteobacteria, Actinobacteria and Acidobacteria in both samples, and they were the most responsive phyla to change in study samples. As shown in
Regarding proteobacteria phylum there is a decrease of the 18% in dead soils, comparing with active soils. The classes Alpha, Gamma, Beta and Delta are in all samples; however abundance in each sample was different. In dead soils there is a decrease of the percentage (33%) comparing with proteobacteria present in active soils (51%). The Alphaproteobacteria were more abundant 26% and 18.8 % in active and dead sample respectively, while Gammaproteobacteria in active peatland was 7% higher that their presence in dead peatland. These results are in concordance to that published by [
The Actinobacteria are a group of bacteria with a highly active secondary metabolism, they are found in large amounts in the peat layers, decomposing cellulose and other plant polymers [
One of the most abundantly distributed bacterial groups in the environment corresponds to Acidobacteria [
DeBruyn [
With regard the phylum Bacteroidetes, have colonized virtually all types of habitats on Earth [
Latescibacteria with cyanobactyeria are present in low proportions (1%). Latescibacteria, little is known about this phylum; however Youssef et al., 2015 suggest that latescibacteria transform algal detritus sinking from sunlit surface waters into fermentation products to contribute to microbial food webs in waters bellow. On the other hand some members of Letescibacteria may be capable of forming greigite magnetosomes, and play unrecognized roles in iron and sulfur cycles [
Although, cyanobacteria dominated the bacterial populations of many extreme environments [
From the active peatland samples, it was possible to isolate different genera of cyanobacteria (
Diatoms and cyanobacteria were isolated from preserved peatland using BG11 medium. Four type of cyanobacteria were identified: Oscillatoria sp.; Lyngbya sp.; Nostoc sp. and Dolichospermum sp. and with regard diatoms five type grew: Ulnaria sp.; Cocconeis placentula; Pinnularia sp.; Nitzschia sp., and Rhopalodia sp. (
It is known that the diatoms respond quickly to any subtle changes in the environmental conditions and hence they are the most promising tools in biomonitoring [
This work began the studies of soils associated with peatland in different states of preservation. Although this is only a first approach to the microbial ecology of
these environments, it can be proposed that the loss of water causes great changes in the physical-chemical characteristics of the soil, which leads to a modification of the microbiota.
As conclusion, the results showed that, in the dead peatland samples there was a decrease of Proteobacteria mainly Alpha and Gamma, moreover an increase of Acidobacterias and Gematimoidetes in approximately 5% was observed. On the other hand Actinobacteria phyla increased markedly in dead peatland samples. Evidently is more resistant to the extreme conditions. The microbial response to desiccation would reflect adaptation strategies. The recovery of these lands should not only consist on the hydration of the soils but also in the bioinoculation of the native organisms. In that way, proteobacteria isolated from healthy soils would be the main candidates to develop a bioinoculation starter.
Ongoing research is developing inoculums with microorganisms isolated from ¨healthy soils¨ in order to produce a biofertilizer for the recovery of peatland dried by miner activities in Andean Altiplane.
The authors acknowledge the generous financial support by the PICT V Bicentenario 2010 1788 Project (FONCyT, Argentina). Authors are researchers from the National Research Council (CONICET) in Argentina and from the National Universities of Tucumán. This work was performed in the context of Proyecto “Análisis de Adaptación al Cambio Climático en Humedales Andinos”. ID: 6188775-8-LP13. Ministerio del Medio Ambiente, Región de Antofagasta (http://portal.mma.gob.cl/).
Belfiore, C., Fernandez, A., Santos, A.P., Contreras, M. and Farías, M.E. (2018) Characterization and Comparison of Microbial Soil Diversity in Two Andean Peatlands in Different States of Conservation-Vega Tocorpuri. Journal of Geoscience and Environment Protection, 6, 194-210. https://doi.org/10.4236/gep.2018.64012