Environmental variations in a semi-enclosed embayment (Amvrakikos Gulf, Greece) – reconstructions based on benthic foraminifera abundance and lipid biomarker pattern

[摘要] The evolution of environmental changes during the last decades and theimpact on the living biomass in the western part of Amvrakikos Gulf wasinvestigated using abundances and species distributions of benthicforaminifera and lipid biomarker concentrations. These proxies indicatedthat the gulf has markedly changed due to eutrophication. Eutrophication hasled to a higher productivity, a higher bacterial biomass, shifts towardsopportunistic and tolerant benthic foraminifera species (e.g. Bulimina elongata, Nonionella turgida,Textularia agglutinans, Ammonia tepida) and a lower benthic species density. Close to the Preveza Strait(connection between the gulf and the Ionian Sea), the benthic assemblageswere more diversified under more oxygenated conditions. Sea grass meadowslargely contributed to the organic matter at this sampling site. Theoccurrence of isorenieratane, chlorobactane and lycopane supported by oxygenmonitoring data indicated that anoxic (and partly euxinic) conditionsprevailed seasonally throughout the western part of the gulf with moresevere oxygen depletion towards the east. Increased surface watertemperatures have led to a higher stratification, which reduced oxygenresupply to bottom waters. Altogether, these developments led to massmortality events and ecosystem decline in Amvrakikos Gulf.

[学科分类] 地球化学与岩石