Bacterial diversity of Bhitarkanika mangrove ecosystem, Odisha, India

Abstract

Bhitarkanika estuary is a highly diverse tropical mangrove ecosystem situated along the river delta of Brahmani and Baitarani before meeting the Bay of Bengal. Large number of heterotrophic bacteria present within the sediment and water are involved in different ecological functions and are capable of interfering in nutrient cycling thereby biological productivity. Heterotrophic bacterial diversity with respect to seasonal variation of several ecological parameters was studied from the five transects namely Dangmal, Ekakula, Gupti, abalikathi and Kalibhanjadiha, within this ecosystem. During monsoon, highest heterotrophic bacterial population was recorded at Dangmal (39.10±3.60x103 cfu/ml and 43.93±5.28x105 cfu/g) and lowest total heterotrophic bacterial population was recorded from Ekakula (7.95±2.05x103 cfu/ml and 6.8±2.17x105 cfu/g) from both the water and sediment samples respectively. During summer, highest heterotrophic bacterial population was recorded at Habalikathi sediment sample (165.58±41.76x104 cfu/g) and Kalibhanjadiha water sample 10.287±11.82x103 cfu/ml) whereas lowest was recorded from Gupti sediment sample (3.835±3.41x104cfu/g) and Ekakula water sample (1.843±1.52x103 cfu/ml). Physico-chemical parameters such as pH, Organic carbon content, Organic matter content, Conductivity, CEC, Temperature, TDS, Ammonia content, Phosphate content, Nitrate content, Chloride content, Salinity, Dissolved Oxygen were studied to understand the impact of seasonal variation on heterotrophic biodiversity. Culture independent bacterial diversity from sediment and water samples were studied by performing illumina sequencing of V3-V4 region of 16S rRNA which showed that Dangmal sediment sample contain the highest number of bacterial species (21,207 species) whereas Ekakula sediment sample contain the lowest (5,077 species). In case of water sample, highest no of bacterial species was recorded in Habalikhati (34,601 species) and lowest was recorded in Gupti (24,846 species). Species richness and chao 1 index was also carried out using alphadiversity estimation followed by refraction curve and rank abundance plot for the sediment and water samples. Comparison between microbial communities were done using Jaccard and Bray-Curtis index. This study revealed that unculturable fraction of bacteria varies greatly with respect to the culturable method. Predominant genera are Acidovorax, cinetobacter, Bacillus, Bergeriella, Burkholderia, Clostridium, Corynebacterium, Enterobacter, Proteobacteria, Escherichia, Moraxella, Neisseria, Pseudomonas, Serratia, Staphylococcus and Yersinia from monsoon samples and Clostridium, Acidovorax, Burkholderia, seudomonas, Streptococcus, Neisseria and Bacillus from summer samples. The distribution and diversity of the heterotrophic bacterial population has not been well documented for Bhitarkanika mangrove ecosystem. Therefore, this study will form the database for bacterial genera available in Bhitarkanika Mangrove ecosystem.