Geography & Environmental Science Seminar Seminar

Speakers:

Yanna Fidai – Environmental Change & Sustainability, School of Geography and Environmental Science

Title: Documenting Sargassum blooms in the Gulf of Guinea from 2002-2020

Sargassum seaweed blooms are an emerging environmental challenge across the tropical Atlantic region where vast blooms of holopelagic Sargassum have appeared on the ocean surface in the Spring and Summer months since 2011. The floating blooms make landfall and have a variety of socio-economic and ecological impacts on coastal communities, including on aquaculture, tourism and on biodiversity. A systematic review of global evidence of Sargassum bloom monitoring shows some key research gaps in the evidence base of floating and landing influxes, notably: most research focuses on open-ocean floating blooms, and research on beach landings is comparatively limited; specific countries or water bodies, including the Gulf of Mexico, the Caribbean and North Atlantic Ocean are the focus of research and neighbouring or regional shorelines, for example, West Africa and Central America are under-researched; methods for quantifying Sargassum biomass volume (including dry/wet weight, unit of measurement, and spatial extent of calculations) were inconsistent; in many publications Sargassum species identification was omitted. Few, if any, empirical publications document long term continuous monitoring of Sargassum blooms in large areas. With a focus on the under-researched parts of West Africa, this research analyses remotely sensed data (from the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra satellite) to detect Sargassum blooms and establish a long term (18 year) estimate of Sargassum ocean coverage patterns. ENVI geospatial image analysis software and Interactive Data Language (IDL) are used to process the remote sensing images and apply the Sargassum detection algorithm Alternative Floating Algal Indices (AFAI). The expected results would utilise a time-series analysis of data spanning 2002-2020 to characterise the annual and seasonal trends of Sargassum bloom coverage in the Gulf of Guinea. Further comparison with other algorithms and use of different forms of ground data to validate remote sensing based estimation will be presented.

Dr Pauline Delorme – Landscape Dynamics and Ecology, School of Geography and Environmental Science

Title: The emergence of aeolian sand dunes

Sand dunes originate from complex interactions between fluid flow, bed morphology and sand transport. The coupling between flow and sand transport controls the bed morphology, and through feedback, the ground surface strongly modifies the airflow dynamics. It is therefore necessary to quantify the relationship between these three parameters to understand the mechanisms of dune nucleation and growth. The development of a dune pattern involves localized deposition inducing bedform formation, which will then, under favourable conditions, produce dunes. Some environmental factors are already recognized as critical ingredients to generate sand deposition: changes in surface characteristics and bed instability.

This talk firstly presents a field study of the emergence of dunes on a flat sandy surface and secondly presents a theoretical model showing the influence of the change in the surface characteristics to explain the patch initiation.

Speaker Information

Yanna Fidai - Postgraduate Research Student within Geography and Environmental Science at the University of Southampton.

Dr Pauline Delorme - Post-doc in Aeolian Geomorphology (TOAD project) within Geography and Environmental Science at the University of Southampton.