CT - DCIV - Artigos publicados em periódicos
URI Permanente para esta coleçãohttps://repositorio.ufrn.br/handle/1/168
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Navegando CT - DCIV - Artigos publicados em periódicos por Autor "Amado, André Megali"
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Artigo Effects of seasonality, trophic state and landscape properties on CO2 saturation in low-latitude lakes and reservoirs(Elsevier, 2019-05) Junger, Pedro Ciarlini; Dantas, Fabíola da Costa Catombé; Nobre, Regina Lucia Guimarães; Kosten, Sarian; Venticinque, Eduardo Martins; Araújo, Fernando de Carvalho; Sarmento, Hugo; Angelini, Ronaldo; Terra, Iagê; Gaudêncio, Andrievisk; They, Ng Haig; Becker, Vanessa; Cabral, Camila Rodrigues; Quesado, Letícia; Carneiro, Luciana Silva; Caliman, Adriano; Amado, André MegaliThe role of tropical lakes and reservoirs in the global carbon cycle has received increasing attention in the past decade, but our understanding of its variability is still limited. The metabolism of tropical systems may differ profoundly from temperate systems due to the higher temperatures and wider variations in precipitation. Here, we investigated the spatial and temporal patterns of the variability in the partial pressure of carbon dioxide (pCO2) and its drivers in a set of 102 low-latitude lakes and reservoirs that encompass wide gradients of precipitation, productivity and landscape properties (lake area, perimeter-to-area ratio, catchment size, catchment area-to-lake area ratio, and types of catchment land use). We used multiple regressions and structural equation modeling (SEM) to determine the direct and indirect effects of the main in-lake variables and landscape properties on the water pCO2 variance. We found that these systems were mostly supersaturated with CO2 (92% spatially and 72% seasonally) regardless of their trophic status and landscape properties. The pCO2 values (9–40,020 μatm) were within the range found in tropical ecosystems, and higher (p < 0.005) than pCO2 values recorded from high-latitude ecosystems. Water volume had a negative effect on the trophic state (r = −0.63), which mediated a positive indirect effect on pCO2 (r = 0.4), representing an important negative feedback in the context of climate change-driven reduction in precipitation. Our results demonstrated that precipitation drives the pCO2 seasonal variability, with significantly higher pCO2 during the rainy season (F = 16.67; p < 0.001), due to two potential main mechanisms: (1) phytoplankton dilution and (2) increasing inputs of terrestrial CO2 from the catchment. We conclude that at low latitudes, precipitation is a major climatic driver of pCO2 variability by influencing volume variations and linking lentic ecosystems to their catchmentsArtigo Extreme droughts drive tropical semi-arid eutrophic reservoirs towards CO2 sub-saturation(Associação Brasileira de Limnologia, 2018-04-05) Becker, Vanessa; Mendonça Júnior, Jurandir Rodrigues de; Amado, André Megali; Vidal, Luciana de Oliveira; Mattos, ArthurAim: This study aimed to evaluate the carbon dioxide (CO2) dynamics in tropical semi-arid reservoirs during a prolonged drought period as well as to test if the trophic state affects the CO 2 saturation. Methods: This study was performed in four reservoirs located in the tropical semi-arid region in the northeast of Brazil. All samplings were performed between 9 and 12 am using a Van Dorn Bottle. Samples for partial pressure of carbon dioxide (pCO2) measurements were taken in the sub-surface as well as samples for total phosphorus and chlorophyll-a. Correlation analysis and linear regression were used to detect relations among the calculated pCO2, water volume and chlorophyll-a. Results: The water level reduction due to atypical droughts caused chlorophyll-a concentrations to increase, which in turn, led to CO 2 reduction in the water. However, CO2 concentrations were very variable and an alternation between CO 2 sub-saturation and super-saturation conditions was observed. This paper showed that water volume and chlorophyll-a were important regulators of CO2 in the water, as well as important carbon balance predictors in the tropical semiarid reservoirs. Conclusions: The results of this paper indicate that the eutrophication allied to drastic water level reductions lead to a tendency of autotrophic metabolism of these systems