Assessing the microbial community structure’s diversity associated with nutrients concentration in the natural wetland systems
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Date
2018
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University of Zululand
Abstract
Microbial communities play a major role in natural wetlands systems biogeochemical cycles. Therefore, understanding the association between their composition, diversity and environmental parameters is significant in order to understand soil microbial ecology associated with nutrients concentration. Such knowledge may enhance the improvement in the management and protection of wetland systems, as nutrients are essential for wetland plant growth. Despite their usefulness, they promote toxin-producing cyanobacteria and facilitates algal biomass growth that cause undesirable eutrophication and oxygen depletion when present in excess. Nutrient pollution therefore is one of the most widespread and challenging environmental problems in the water that usually result to serious environmental and health challenges.
For this study, water and sediment samples were collected over a period of twelve months from Lake Icubhu, which is a fresh water wetland, and Nhlabane mouth Estuary. The physicochemical properties such as temperature, potential hydrogen (pH), chemical oxygen demand (COD), total suspended solids (TSS) and nutrients were analyzed in water samples. The InoLab_IDS multi 9310 was used for the analysis of temperature and pH, while the filter technique was used for the analysis of TSS concentrations, and spectrophotometric methods were used for the analysis of nutrients and COD concentrations, using respective kits.The pH ranged between 6.5 -7 in Lake Icubhu, and 6.9 – 7.3 in Nhlabane Estuary. Nitrate and nitrite were highest in the autumn (3.2 mg/l – 0.5 mg/l),and least in the summer (0.1 mg/l – 0.01 mg/l) for both wetlands, phosphorus and ammonium were also examined. The results of nutrients obtained in this study demonstrated a significant threat to the studied wetlands when compared to the South African standard for Water Quality Guidelines of Aquatic ecosystem throughout the study period. It has been observed and concluded from the values obtained in this study that seasonal variations contributed to nutrient cycling. Correlation coefficient of each wetland system were also analyzed in order to understand the pollution load, as well as the effect of physicochemical parameters on the nutrients. The correlation results revealed that all these parameters are interrelated with each other and should be considered together. Specifically, the Illumina Miseq Sequencing analysis method was used in this study to identify microbial community structures. After sequencing, the most represented bacterial community was Proteobacteria in both wetlands. Therefore, the core composition of these bacterial communities consisted of: Proteobacteria, Bacteroides, Actinobacteria, Firmicutes among others. While members of Actinobacteria, bacteroidetes and Acidobacteria were observed in Lake Icubhu, members of Firmicutes, Chloroflexi and Bacteroidetes were also dominant at Nhlabane Estuary. Finally, some representatives of Thermomicrobia, Fusobacteria, Verrucomicrobia and Fusobacteria were also retrieved from some samples. Based on the results of nutrients, microbial diversity and community structuresobtained in this study, it was concluded that seasonal variations and nutrient pollution loads were related to microbial community structures.
Description
A dissertation submitted in fulfilment of the requirements for the Degree of Master of Science in Microbiology in the Department of Biochemistry and Microbiology, Faculty of Science and Agriculture at the University of Zululand, 2018.
Keywords
Nutrients concentration, Natural wetland systems