The biological carbon pump in the 21st century: potential threats of rising sea surface temperature (SST) and coastal pollution by emerging contaminants (ECs)

• Ano de defesa: 2024
• Autor(a) principal: Frazão, Luciana Rocha
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: aquecimento dos oceanos; carbon cycle; ciclo do carbono; CMIP6 models; Giro Subtropical do Atlântico Sul; microbial plankton; modelos CMIP6; ocean warming; plâncton microbiano; PPCPs; South Atlantic Subtropical Gyre; Ubatuba (Brasil); Ubatuba (Brazil)
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21134/tde-21082024-144428/

The thesis presents a compilation of studies conducted with the goal of investigating the main drivers of biological carbon pump (i.e., marine microbial plankton) and the potential effects of the two main threats to ocean carbon cycle in the 21st century: ocean warming and coastal pollution. At first, Chapter I presents an overview of conceptual advances in marine microbial ecology which have led to current well-established models of carbon flows in oligotrophic pelagic ecosystems and the pivotal role of microbial plankton in the biological carbon pump. Additionally, the state of the art of microbial ecology in the South Atlantic Subtropical Gyre (SASG), an ecological important region to global carbon cycle that remains poorly understood, is discussed. In Chapter II, the long-term responses of ocean warming in marine microbes was investigated on a global scale using CMIP6 models and machine learning. All microbial biomass projections (µg C L-1) show a decrease in the late 21st century for the four Shared Socioeconomic Pathways (SSPs) of IPCC. The biomass projections also indicate the expansion of the SASG, and a near-global prevalence of heterotrophy (primary production rates lower than bacterial production), which has obvious implications for the biological carbon pump, and thus, to global carbon cycle and climate regulation. Finally, in Chapter III, the occurrence of pharmaceuticals and personal care products (PPCPs), one of the main classes of emerging contaminants (ECs), was investigated for the first time in the inner shelf of Ubatuba, on the northern cost of São Paulo State (Brazil). LC-MS/MS analysis revealed the presence of 15 compounds, including anti-inflammatories/analgesics, β-blockers, anti-hypertensives, psychoactive drugs, caffeine, cocaine its human metabolite. The spatial distribution of these compounds suggests that lateral advection by coastal currents may transport emerging contaminants, such as those recorded here, far from their original source. The ecological risk (ERA-USEPA) assessed for primary producers indicates moderate to high risk for some of these compounds to photosynthetic carbon fixation, and consequently, to the carbon pathways in pelagic food webs.