http://197.159.135.214/jspui/handle/123456789/946 Thu, 23 Apr 2026 15:10:05 GMT 2026-04-23T15:10:05Z http://197.159.135.214/jspui/handle/123456789/832 Aerosols Optical Properties Profile Characterization over Sao Vincente, Cabo Verde, during the Askos Campaign Moussa Idrissa, Samira Studying the vertical distribution of aerosol particles is essential for understanding their influence on the climate system. One way to evaluate this aspect of aerosols is to discriminate their source and optical properties in the atmosphere column. The main objective of this study was to characterize and vertically analyze aerosol's optical properties profile under distinct aerosol mixture states over São Vicente Island, Cabo Verde, during the ASKOS campaign that took part in July and September of 2021. Thus, the Elastic Extinction (ElEx) method has been applied, which allows aerosol backscattering profile separations by type and estimation of total extinction coefficient. The EIEx application requires particles' complete backscattering profile and vertically resolved particles' linear depolarization ratio at the same wavelength. These values were taken from the eVe lidar system, linear depolarization ratio and lidar ratio values of pure aerosol types that were taken from the literature. The total extinction coefficient profile is then estimated and compared with eVe Raman retrievals and with the results of a PollyXT Raman lidar, also operated in São Vicente during the ASKOS experiment. Based on this method, three study cases have been chosen for detailed discussion. The first and third cases consist of pure Saharan dust in the free troposphere, while in the Marine Boundary Layer (MBL), pure marine and volcanic sulfate were recorded, respectively. Regarding the second study case, a mixed scenario of dust and marine aerosols were found across the MBL and free troposphere. Comparison between the EIEx estimated optical properties profiles (extinction coefficient, lidar ratio) and the eVe and PollyXT lidar retrievals revealed a good general agreement. Nevertheless, differences can be observed in regions where the signal to noise ratio is low, such as close to the top of the aerosol layer and also inside the MBL. These differences in the MBL could be attributed to the presence of pollution particles or the limited ability of the lidars to correctly represent the aerosol optical properties in the near range due to the overlap problem. A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Universidade Técnica do Atlântico, Cabo Verde in partial fulfillment of the requirements for the Master of Science Degree in Climate Change and Marine Science Sat, 01 Jan 2022 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/832 2022-01-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/831 Fluxes of Atmospheric Nutrients during Dust Events to the Atlantic Ocean and their Impact on Regional Ocean Productivity Kabore, Nongma Environmental change and human activities are increasing anthropogenic particle loads in marine ecosystems, affecting phytoplankton growth and production. To understand how oligotrophic ecosystems respond to atmospheric deposition during dust episodes, 22 PM10 samples were collected at the Cabo Verde Atmospheric Observatory (CVAO) station. From these samples, the fluxes of inorganic ions and trace metals deposited and their potential impact on primary production were determined. The samples were collected using a low volume sampler on 37 mm diameter quartz fiber filters from January 27 to February 18, 2022. The investigated species included NO3−, NO2−, NH4+, PO43−, SO42−, K+, Mg2+, Ca2+, Al, Fe, Ti, P, Zn, V, Ni, and Cr. The Copernicus satellite data was used to investigate impacts of dust events on the marine ecosystem. The results showed that the PM10 concentration during the dust events (118.80 μg m−3) was seven times higher than that in the non-dust events (16.64 μg m−3). Chemical analysis showed that concentrations of trace metals and inorganic ions during the dust episodes were very different from those of non-dust days, with increases ranging from 4 to 144% for ions and 3 to 642% for trace elements. The back trajectory analysis indicated that mixing mechanisms during the transport route may affect species concentrations. Zn, NO2−, NH4+, and PO43− had low deposition rates to the ocean after dust storms, while the other nutrients such as NO3−, SO42−, K+, Mg2+, Ca2+, Al, Fe, and Ti showed faster deposition rates. Using a non-linear deposition model, we estimated dry deposition fluxes, with mean fluxes of dissolved inorganic nitrogen (DIN = NO3− + NO2− + NH4+) and PO43− of 2.6 and 0.04 μmol m−2 d−1, respectively, during dust events, and 1.8 and 0.03 μmol m−2 d−1, respectively, during non-dust events. The inorganic N/P ratios were above the Redfield ratio, indicating increased nutrient input and potential phosphorus limitations in surrounding waters. Satellite data showed an increase in chlorophyll a and phytoplankton biomass after dust episodes. We have successfully captured atmospheric nutrient input fluctuations through laboratory measurements of nutrient content in particulate matter. This has improved our knowledge of dust deposition impacts on marine planktons and highlights the need for more research to understand the species-specific response to high nutrient inputs. A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Universidade Técnica do Atlântico, Cabo Verde in partial fulfillment of the requirements for the Master of Science Degree in Climate Change and Marine Science Sun, 01 Jan 2023 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/831 2023-01-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/830 An Assessment of Seagrass Meadows and Ecosytem Services in Turtle Islands, Sierra Leone. Case Study: Bumpetuk Ndure, Melissa Ekua Seagrasses are unique aquatic plants that provide several vital ecosystem services, including erosion mitigation, habitat for fisheries, and carbon sequestration. Despite these plants’ significant role in the marine environment, they are threatened mainly by human activities. West Africa is amongst the least studied areas of seagrass globally. However, through the ResilienSEA seagrass project, the region now has more data on seagrass. Sierra Leone officially recorded seagrass in 2019. Several monitoring exercises have been undertaken following the discovery to learn more about the seagrass species and raise awareness. This research seeks to add to the ongoing studies in the area. It assesses three specific objectives – i. seagrass ecology, ii. ecosystem services, and iii. people’s perception of seagrass. The ecological assessment included seagrass percentage cover, canopy height, sediment type, and water depth. The result showed low seagrass percentage cover, and the canopy height ranged between 3–10 cm. The sediment is primarily sandy. The open data kit (ODK) assessed objectives two and three. Participants indicated that seagrass in the area supports provisioning, regulatory and maintenance, and cultural services. They were also keen interest in learning more about seagrass and conserving it. A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Universidade Técnica do Atlântico, Cabo Verde in partial fulfillment of the requirements for the Master of Science Degree in Climate Change and Marine Science Sun, 01 Jan 2023 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/830 2023-01-01T00:00:00Z http://197.159.135.214/jspui/handle/123456789/829 Seasonal Variation and Sources of Particulate Matter Induced Air to Sea Nutrient Fluxes in the Eastern Tropical North Atlantic Quaye, Daniel Tetteh Atmospheric nutrient input to the open ocean is a significant nutrient source that affects biological productivity and marine biogeochemistry. In this study, a 3-year time series (2017 –2019) of aerosol samples collected at a remote ocean site in the eastern tropical North Atlantic (ETNA) was used to investigate the sources and seasonal variation of particulate matter (PM10) derived nutrient inputs to this region. The samples were analysed for soluble major nutrients (NO3-, NH4+, and PO43-) and total trace metals (Al, Fe, Mn, V, Ni, Zn and Cu). The average PM10 mass at the site was 51.8 ± 57.6 μg m−3, with particles transported by air masses from four distinct source regions based on back trajectory analysis. During the sampling period, most of the air masses originated in Europe (55.8%) and the Sahel-Sahara region (26.5%). The nutrients deposited into the ETNA were derived from both natural and anthropogenic emissions, with some of the sources exhibiting strong seasonal variability. Dust dominated the contribution to the fluxes of crustally derived elements Al, Mn, and Fe. Mineral dust was also the primary contributor of P; however, in line with previous studies, emissions from the described source regions indicate that biomass burning contributes a larger soluble fraction of P than dust. From the estimated nutrient fluxes, only the seasonal flux of NO3- showed weak variation. The N to P ratio in PM was higher (ranging from 60 to 486) than the Redfield ratio of 16, indicating that atmospheric deposition was constantly P-deficient relative to phytoplankton requirements. Therefore, atmospheric nutrient fluxes are likely to promote P-limitation in the oligotrophic ETNA ocean. As a result, phytoplankton adapted to P stress will be favoured, potentially triggering a cascade effect that impacts plankton community structure and the biogeochemical cycles of N and C. A Thesis submitted to the West African Science Service Center on Climate Change and Adapted Land Use and Universidade Técnica do Atlântico, Cabo Verde in partial fulfillment of the requirements for the Master of Science Degree in Climate Change and Marine Science Sat, 01 Jan 2022 00:00:00 GMT http://197.159.135.214/jspui/handle/123456789/829 2022-01-01T00:00:00Z