AUTHOR=Machaieie Helder Arlindo , Nehama Fialho Paloge Juma , Silva Cleverson Guizan , de Oliveira Eduardo Negri 

TITLE=Satellite assessment of coastal plume variability and its relation to environmental variables in the Sofala Bank

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.897429

DOI=10.3389/fmars.2022.897429

ISSN=2296-7745

ABSTRACT=<p>Monthly composites of remote sensing reflectance at 555 nm wavelength (R<sub>rs</sub>555) from ocean color imagery of the MODIS sensor onboard the Aqua platform were used to characterize the spatial and temporal variability of coastal plume in the Sofala Bank and its relation to river discharge, local rainfall, and wind speed. To achieve the objective, maps of monthly composites of R<sub>rs</sub>555 over the Sofala Bank were inspected and statistical analysis was performed, including correlation, analysis of variance, and wavelet coherence between environmental variables and both plume area and R<sub>rs</sub>555. Climatology of R<sub>rs</sub>555 revealed that both plume dispersion and R<sub>rs</sub>555 values are higher during June to December and lower during January to May. A positive correlation (<italic>r</italic> = 0.77) between wind speed and monthly time series of R<sub>rs</sub>555, and a negative correlation between the Zambezi river discharge (<italic>r</italic> = −0.21) and rainfall (<italic>r</italic> = −0.67) with R<sub>rs</sub>555 were found. These results suggest that variation of suspended matter in the Sofala Bank is mainly controlled by erosion and re-suspension by winds rather than the input of terrigenous matter by the Zambezi River discharge and rainfall, assuming that R<sub>rs</sub>555 can be a valid proxy for the inorganic suspended matter. The southern portion of the Sofala Bank (i.e., near the mouths of the Pungue and Buzi Rivers) presented higher values of R<sub>rs</sub>555 if compared to the center region near Zambezi river mouth and the northern region near Licungo river mouth. The higher R<sub>rs</sub>555 values in the southern region might be associated with higher re-suspension rates due to increased tide mixing, dredging activities, and the shallower nature of bathymetry in the southern region. The dominance of wind in controlling the variability of suspended sediments and the eventual relatively greater contribution of Pungue and Buzi River than the Zambezi in supplying sediments could represent an evidence of weakening of Zambezi River supply of sediments, a process that might have started after damming the Zambezi Catchment.</p>