Browsing by Author "Lukwambe, Betina"

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    Impacts of bioturbation by Venus clam Cyclina sinensis (Gmelin, 1791) on benthic metabolism and sediment nutrient dynamics in a shrimp-clam polyculture pond.
    (ICAR, 2020-09-03) Nicholaus, Regan; Lukwambe, Betina; Mwakalapa, Eliezer Brown; Yang, Wen; Zhu, Jinyong; Zheng, Zhongming
    Dynamics of benthic inorganic nutrients are key biogeochemical components of sediment metabolism and ecosystems. This study investigated the roles of the bivalve Cyclina sinensis (Gmelin, 1791) and its influence on benthic metabolism, nutrient f luxes and sediment oxygen consumption (SOC) in a shrimp-clam polyculture system in comparison with shrimp culture ponds without incorporating clams, in Ningbo Zhejiang China. The benthic inorganic nutrients fluxes (ammonium-NH4 +, nitrate plus nitrite-NO3-+NO2- and phosphate-PO4 3-) and SOC were measured across the sediment-water interface with dark incubation experiments. The results showed that there were significantly higher nutrient fluxes from the sediment into the overlying water (p<0.05 ) in the treatment ponds in the order of NH4 + > PO4 3- > NO3- + NO2-. The SOC varied significantly (p0.05) and was three times higher than that of the control ponds. Water quality (dissolved oxygen, pH, chlorophyll-a and salinity) recorded showed slight variations over time but were not significantly different (p>0.05) between the control and treatment ponds.Sediment organic matter and chlorophyll-a concentration measured in the shrimp-clam ponds varied significantly (p<0.05)as compared to control ponds. The results of this study suggest that the bioturbation activities by C. sinensis promoted the SOC, sediment organic matter degradation and mineralisation process that increased the exchange of nutrients and oxygen uptake between the sediment and the overlying water.
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    The Functional Diversity of Microbial Communities in the Multi‑Compartment Biofilters of Shrimp Mariculture Effluents Using 16S rRNA Metabarcoding.
    (Springer, 2023-07-18) Lukwambe, Betina; Nicholous, Regan; Zheng, Zhongming
    Microbes play important roles in mariculture biofilter systems, such as biogeochemical cycling of nutrients and organic matter degradation. However, their functional diversity for nutrient removal in shrimp mariculture effluents influenced by multi-compartment biofilters remained elusive. This study explored the functional diversity of microbial communities for nutrient removal in the multi-compartment biofilters of shrimp mariculture effluents. We explored the bacterial taxonomy using Illumina sequencing of the 16S rRNA gene, and the ecological functional diversity of the bacteria was assigned using Functional-Annotation-of-Prokaryotic-Taxa analysis (FAPROTAX). According to the Illumina dataset, there was a high heterogeneity, with phase two (P2) treatment showing significant reversible shifts in microbial communities’ population and biogeochemical dynamics relative to phase one (P1). The genera Candidatus aquiluna, Marivita, HTCC , Anaerospora, and Arcobacter were abundant in both stages and may have the functional capability of biodegrading inorganic matter (OM). FAPROTAX results showed that the predominant functional groups (P1 and P2) for nutrient removal were related to chemo-heterotrophy. Furthermore, the nitrate-reduction and nitrate-ammonification were highly significant (P < 0.05) at P2, resulting in an average removal efficiency of 81.39% for total nitrogen (TN) and 80.63% for total phosphorus (TP). The results suggested that incorporating multicompartment biofilters in the system provides a suitable substrate environment for the potential proliferation of Proteobacteria, Nitrospirae, and Bacteroidetes. Overall, this study enlightens the potential roles of the microbial communities under the influence of biofilters in promoting the feasible and most efficient bioremediation approaches for mariculture effluents.