Project description:Heavy metals contamination in aquatic ecosystems has been a major concern, however, no information is available about the concentrations, depth distributions and ecological risks of heavy metals in sediments cores from microtidal lagoonal ecosystem in Lagos, Nigeria. Four sediment cores were collected using a 50?cm?×?3.5?cm Wildco® hand corer. Elemental determinations were carried out using the Microwave Plasma Atomic Emission Spectrometry (4200 MP-AES) after extraction. The concentrations of heavy metals in the sediment cores indicated enhanced degree of contamination influenced by anthropogenic discharges especially industrial effluents. Vertical depth distributions indicated varied depositional periods largely controlled by increasing anthropogenic land-based activities. The remarkable metal pollution of core sediments raises the concern potential sources of metals to the lagoonal ecosystem and ecological risks to the biota, humans, and the environment. The results of elemental concentrations should be considered as baseline data for heavy metals in sediments in the region.
Project description:Ammonia-oxidizing archaea (AOA) have been reported at high abundance in much of the global ocean, even in environments such as pelagic oxygen minimum zones (OMZs), where conditions seem unlikely to support aerobic ammonium oxidation. Due to the lack of information on any potential alternative metabolism of AOA, the AOA community composition might be expected to differ between oxic and anoxic environments, indicating some difference in ecology and/or physiology of the AOA assemblage. This hypothesis was tested by evaluating AOA community composition using a functional gene microarray that targets the ammonia monooxygenase gene subunit A (amoA). The relationship between environmental parameters and the biogeography of the Arabian Sea and the Eastern Tropical South Pacific (ETSP) AOA assemblages was investigated using principal component analysis (PCA) and redundancy analysis (RDA). In both the Arabian Sea and the ETSP, AOA communities within the core of the OMZ were not significantly different from those inhabiting the oxygenated surface waters above the OMZ. The AOA communities in the Arabian Sea were significantly different from those in the ETSP. In both oceans, the abundance of archaeal amoA gene in the core of the OMZ was higher than that in the surface waters. Our results indicate that AOA communities are distinguished by their geographic origin. RDA suggested that temperature was the main factor that correlated with the differences between the AOA communities from the Arabian Sea and those from the ETSP. Physicochemical properties that characterized the different environments of the OMZ and surface waters played a less important role than did geography in shaping the AOA community composition.
