Geochemistry and sedimentary photopigments as proxies to reconstruct past environmental changes in a subtropical reservoir

Author(s)

Cardoso-Silva, Sheila ^{[1, 2]} ; Soares Silva Mizael, Juliana Oliveira ^[3] ; Frascareli, Daniele ^[3] ; Lopes Figueira, Rubens Cesar ^[1] ; Pompeo, Marcelo ^{[3, 4]} ; Vicente, Eduardo ^[5] ; Moschini-Carlos, Viviane ^[3]

Affiliation

^[1] Univ Sao Paulo, Oceanog Inst, Sao Paulo, SP - Brazil

^[2] Fed Univ Acre UFAC, Ecol & Nat Resources Management Program, Rodovia BR 364, Km 4, BR-69920900 Rio Branco, AC - Brazil

^[3] State Univ Sao Paulo UNESP, Inst Sci & Technol, Environm Sci Program, Sorocaba, SP - Brazil

^[4] Univ Sao Paulo, Biosci Inst, Ecol Dept, Sao Paulo, SP - Brazil

^[5] Univ Valencia, Microbiol & Ecol Dept, Valencia - Spain

• Document type: Journal article
• Source: Environmental Science and Pollution Research; JAN 2022.
• Web of Science Citations: 0

Abstract

Sediment cores were used to establish past environmental impacts associated with eutrophication, erosion and metal contamination in the subtropical Atibainha reservoir (Sao Paulo State, Brazil). We hypothesize that: (1) the levels of nutrients, determined by a spectrophotometric method, reflect the contributions of these elements over time and (2) changes in sedimentation rates, determined by Pb-210 geochronology, and metal flows, determined by ICP-AEOS, are related to anthropic activities. Stratigraphic changes in the analysed variables were used to divide the sediment cores into three intervals, according to PCA and cluster analysis (Euclidian distances, Ward's method). Interval I, composed by the period prior to operation of the reservoir, was influenced by organic matter levels. Interval II, between 1967 and 1993 (PC2: 14.94% of the total variability), a period of minor impacts, was mainly influenced by Mn (eigenvalue of 0.71) and Zn (0.74). Interval III, which included sediment deposited between 1993 and 2015 (PC1: 60.28% of the total variability), was influenced by the highest levels of the pigments lutein (0.86), zeaxanthin (0.90) and fucoxanthin (0.65), together with total nitrogen (0.78) and sedimentation rate (0.91), suggesting changes in the phytoplankton community composition probably associated to the intensification of eutrophication and erosion processes. Despite the limitations of applying paleolimnological techniques in reservoirs and the use of pigments as proxies in regions with higher temperatures, it was observed that the anoxic conditions and the aphotic environment in the hypolimnion acted to preserve pigments associated with the groups Chlorophyta (lutein), Cyanobacteria (zeaxanthin) and Bacillariophyta (fucoxanthin). The isolated analysis of nutrients was not sufficient to make conclusive inferences regarding the eutrophication history, since the levels of TP tended to decrease over time, in contrast to an increase in the levels of TN. Despite intensification of eutrophication and erosion, associated to anthropic activities, no signs of metal contamination were recorded. (AU)

• FAPESP's process: 19/10845-4 - Water quality of São Paulo reservoirs: the weight of evidence
• Grantee: Marcelo Luiz Martins Pompêo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/22581-8 - The European Union's Water Framework Directive: applications to Brazilian reservoirs reality
• Grantee: Marcelo Luiz Martins Pompêo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/15397-1 - Organic Carbon cycling in Water Reservoirs of Brazil and Germany: influence of land use and hydrology- ORCWAR
• Grantee: Daniele Frascareli
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/17266-1 - The European Union Water Framework Directive: applications using the phytoplankton as an environmental discriminator in Brazilian reservoirs
• Grantee: Viviane Moschini Carlos
• Support Opportunities: Regular Research Grants