Spatial Variations of the Bacterial Diversity in an Alkaline Lake

Abstract

Lake Iznik is one of the largest lake of Turkey covering 308 km surface area with 65 m max. depth. The lake has alkaline characteristics (Akcaalan et al. 2014). It is a mesotrophic lake that becomes stratified between June-September and well mixed between OctoberApril. Although there are almost 200 lakes in Turkey, there is very little published research focused on the bacterial diversity structures (Ozbayram et al. 2020.) The specific objective of this study was to evaluate the bacterial community profile in the surface water and sediment of the alkaline lake during the winter turnover. For this purpose, the samples were collected from 6 stations (5 on the shore and 1 in the middle of the lake) in February 2020 when the lake was completely mixed. In addition to the surface water and sediment samples, a sample was also collected from the depth of 40 m from the station located in the mid-lake. The water samples were filtered from a 0.22 μm filter and the sediment samples were taken into sterile plastic containers. The total DNAs were extracted using the NucleoSpin® Soil Kit (Macherey-Nagel, Germany) following the manufacturer’s instructions. Bacterial community profiles of the samples were analyzed by 16S rRNA gene-targeted sequencing using Illumina® MiSeqTM. Physicochemical parameters were measured as explained by Ozbayram et al. 2020. The pH was between 8.29-8.67 and the Electrical Conductivity (EC) was in the range of 734-996 μS/cm (Suppl. material 1 -Table S1). Whereas the Dissolved Oxygen (DO) levels were measured as 10.12-11.65 mg/L in the surface waters, it was 9.72 mg/L in the 40 m. Among all samples, the highest value of the Shannon and Pielou s evenness indices were ‡ ‡ ‡ ‡ ‡