Abstract
Abstract Aim: 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 CO2 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 CO2 reduction in the water. However, CO2 concentrations were very variable and an alternation between CO2 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.
Highlights
Inland aquatic ecosystems play an important role in the Global carbon cycle because they are responsible for processing great amounts of organic matter from terrestrial ecosystems and for emitting carbon dioxide (CO2) to the atmosphere (Cole et al, 2007; Tranvik et al, 2009; Raymond et al, 2013)
Aim: 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 CO2 saturation
It is already documented that the regular annual dry periods in this area increase the trophic state of the reservoirs and they are usually mostly in eutrophic conditions (Brasil et al, 2016)
Summary
Inland aquatic ecosystems play an important role in the Global carbon cycle because they are responsible for processing great amounts of organic matter from terrestrial ecosystems and for emitting carbon dioxide (CO2) to the atmosphere (Cole et al, 2007; Tranvik et al, 2009; Raymond et al, 2013). Louis et al, 2000; Friedl & Wüest, 2002; Humborg et al, 2002; Roland et al 2010) These ecosystems are relevant to the global carbon balance because they are responsible for an important fraction of the CO2 emission to the atmosphere from inland waters (Oki & Kanae, 2006; Barros et al, 2011). Most of the CO2 emission (up to 70%) through reservoirs occurs in tropical regions (St. Louis et al, 2000)
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