Benthic foraminiferal distribution influenced by rivers on the northern gulf of Cadiz continental shelf

• Autor(a) principal: Alexander, Olivia Helen Barbara
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/12384
• topic: Rio Tinto-Odiel; Rio Guadalquivir; Ecologia; Bioindicadores; Associações de foraminíferos; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

Benthic foraminifera are widely used as bioindicators due to their sensitivity to environmental stimuli and global distribution. Understanding their ecology is a fundamental factor in interpreting their distribution patterns. This dissertation assesses the distribution of benthic foraminifera as related to rivers on the northern Gulf of Cadiz continental shelf, a highly productive zone with strong fluvial influences. In this study, the distribution of living (stained) and dead benthic foraminifera from six surface sediment samples, collected on the Gulf of Cadiz continental shelf, along two profiles off the Tinto-Odiel and Guadalquivir Rivers, were analyzed. The distribution of the living fauna was compared with the main oceanographic parameters, temperature and salinity, in order to obtain indicator species in present-day shelf environments. 13 species at relatively high abundances (>5%) were identified for the living assemblage. From these, two biofacies were defined and related with their abundances and locations on the shelf. Biofacies I, associated with higher depths (55 m to 91 m), contained Brizalina spathulata/dilatata, Cassidulina laevigata, Cassidulina minuta, Epistominella vitrea, Bulimina elongata, Rectuvigerina phlegeri, and Bolivina striatula. Biofacies II, associated with shallower depths (23 m to 39 m) and river influence, contained Brizalina seminuda, Nonionella stella, Bolivina ordinaria, Textularia earlandi, Hopkinsina atlantica, Ammonia beccarii/tepida. These results were compared with samples collected in 2001, which had some differences in the most abundant (>5%) species, relative to those found in 2015. These findings will constitute a baseline for future studies on the ecology of foraminifera and their distribution on the northern Gulf of Cadiz continental shelf.