Structure, diversity and potential metabolic activity of prokaryotic communities of Ebro Delta wetlands (Spain) as revealed by 16S rRNA gene amplicon sequencing

The monitoring of the structure and potential function of the prokaryotic assemblages of aquatic ecosystems can be used for the assessment of ecosystem health. In this work, we analysed by 16S rRNA gene amplicon massive sequencing the aquatic and sediment prokaryotic communities inhabiting three wetlands located in Ebro river Delta (Spain), which differ in their salinity and trophic status. We extracted the DNA from both matrices and sequenced the V4 region of the prokaryotic 16S rRNA gene by Illumina sequencing. The raw sequences obtained were processed and clustered in ZOTUs, which are sequences at 100% identity that were the basis for the structural and statistical analyses. Our results showed that water communities have less diversity and evenness than sediment communities. Moreover, statistical analyses showed that salinity is the main environmental factor that affects the structuration of sediment prokaryotic communities, while seasonality is also a very additional important environmental driver for aquatic communities. We also studied the relationship between the environmental factors and the potential metabolism of the aquatic and sediment prokaryotic communities, specifically for the main metabolic processes of the C-cycle. Focusing on sediment, we observed that methanogenic archaea are present not only in freshwater environments but also in the saline wetlands, though the observed methane emissions decreased with salinity. To explain this, we studied the potential activity of sulfate-reducing bacteria (SRB) and methanogenic archaea inferring the expression of genes dsrB and mcrA, which are gene markers for dissimilatory sulfate reduction and methanogenesis, respectively. We observed that, in saline wetlands, the potential activity of methanogens decreases because SRB bacteria outcompete them due to the higher sulfate availability enhancing sulfate-reduction. In the sediment communities of low salinity wetlands the relevance of methanogens is lower in terms of relative abundance, but the methane emissions are higher due to the lower sulfate availability. On the other hand, aquatic methanotrophic bacteria are very important in the net balance of methane emissions in Ebro Delta wetlands, as their relative abundance in the water column influences the amount of methane that is finally released to the atmosphere. In conclusion, our study deepens in the relationship between prokaryotic community structure and function in deltaic wetlands, giving a comprehensive overview of factors influencing the ecological health and certain processes, such as methane emissions, in deltaic systems.

Methods of engineering geophysics in the control of the reclamation state of agricultural land

The article provides information about the possibility of monitoring the reclamation situation of agricultural land by studying the soil-lithological profile by means of electrometric methods. The essence of the applied resistance method is the study of the soil layer using constant or variable electric fields. For engineering geophysical works in sand-clay sections typical of the Stavropol Territory, various variants of research technologies are presented. The conducted studies have shown the effectiveness of the electrometric method of vertical electrical sounding, which allows, based on surface observations with a minimum amount of control drilling and analytical work, to obtain operational information about changes in the area and depth of such an important parameter for assessing the reclamation state of soils as their specific electrical resistance, depending on humidity and salinity. The VEZ method, in addition to the available information about waterlogged and saline wetlands observed on the earth’s surface by traditional methods, allows us to obtain information about hidden unfavorable zones: about changes in their configuration in area and depth.

Contribution to the Study of Diversity, Distribution, and Abundance of Insect Fauna in Salt Wetlands of Setif Region, Algeria

The present study aims to assess entomofauna biodiversity at three saline wetlands, located in Setif region, Northeastern Algeria. To determine the predominant environmental factors in the distribution of entomofauna, six different stations and three transects in each station were chosen according to the distribution of plant and soil salinity in each transect. Results were analysed, and different ecological indexes and analytical methods were applied, from 2016 to 2017. The total of individual insects belonging to 9 orders, 71 families, and 131 species were collected from the three sites. The highest abundance was in Coleoptera (38.17%) while the lowest abundance was found in Ephemeroptera (1.53%). The highest number of individuals (11438) was found in Bazer site in 2016, while the lowest number of individuals (4921) was in site Chott Frain in 2017. The highest abundance of insects (109) was recorded in transect BS1T16, and the lowest abundance of species was recorded in transect HS1T36. Diversity and equitability indices showed highest values in HS1T16 (H = 4,356) and HS1T37 (E = 0.7282). Some ecological parameters showed a significant relationship between the insects occurrence, distribution of plants, and type of soil.