Carbon Dioxide Fluxes to the Atmosphere From Waters Within Flooded Forests in the Amazon Basin

Abstract

Inundated tropical forests are underrepresented in analyses of the global carbon cycle and constitute 80% of the surface area of aquatic environments in the lowland Amazon basin. Diel variations in CO2 concentrations and exchanges with the atmosphere were investigated from August 2014 to September 2016 in two flooded forests sites with different wind exposure within the central Amazon floodplain (3°23′S, 60°18′W). CO2 profiles and estimates of air–water gas exchange were combined with ancillary environmental measurements. Surface CO2 concentrations ranged from 19 to 329 μM, CO2 fluxes ranged from −0.8 to 55 mmol m−2 hr−1 and gas transfer velocities ranged from 0.2 to 17 cm hr−1. CO2 concentrations and fluxes were highest during the high water period. CO2 fluxes were three times higher at a site with more wind exposure (WE) compared to one with less exposure (WP). Emissions were higher at the WP site during the day, whereas they were higher at night at the WE site due to vertical mixing. CO2 concentrations and fluxes were lower at the W P site following an extended period of exceptionally low water. The CO2 flux from the water in the flooded forest was about half of the net primary production of the forest estimated from the literature. Mean daily fluxes measured in our study (182 ± 247 mmol m−2d−1) are higher than or similar to the few other measurements in waters within tropical and subtropical flooded forests and highlight the importance of flooded forests in carbon budgets.

Fisheries management influences phytoplankton biomass of Amazonian floodplain lakes

“…Barbosa & Padisák, 2002;Rugema et al, 2019), as a function of water column heating due to solar radiation incidence, causing the actively mix layer depth to be shallower around noon (Amaral et al, 2018;MacIntyre & Melack, 1984). These daily vertical movements were shown to affect nutrients (Melack & Fisher, 1990) and greenhouse gases dynamics (Amaral et al, 2018(Amaral et al, , 2020Barbosa et al, 2020), but the impact to phytoplankton biomass and primary production on Amazon floodplain lakes are yet to be assessed. We recommend that future studies should focus on seasonal temperature profile data, in combination with nutrients measurements, Chl-a, and direct estimates of primary productivity rates (e.g.…”

Large Seasonal and Habitat Differences in Methane Ebullition on the Amazon Floodplain

“…Limnological features and further site descriptions are provided in Amaral et al. (2018, 2020) and Barbosa et al. (2018, 2020).…”

“…At each site, three habitats were included, if present and accessible: open water, floating herbaceous plants (referred to as macrophyte mats), and flooded forests (Figure 1); Amaral et al. (2018, 2020) and Melack et al. (2021) provide additional imagery illustrating these habitats.…”

“…Flooded forests, floating herbaceous plants and open waters, common aquatic habitats on Amazon floodplains, occur in Janauacá Lake (Figure 1). Limnological features and further site descriptions are provided in Amaral et al (2018Amaral et al ( , 2020 and Barbosa et al (2018Barbosa et al ( , 2020.…”

Limnological perspectives on conservation of floodplain lakes in the Amazon basin

“…Sampling and analytical methods are described in Amaral et al (2020) and Barbosa et al (2020). Publications with information about limnology, biogeochemistry and hydrology of Lake Janauacá include Amaral et al (2018, 2020), Barbosa et al (2020), Bonnet et al (2017), Brito et al (2017), Forsberg, Melack, et al (2017), Junk (1970), and Schmidt (1973a, 1973b). Tables 1 and 2 summarize ranges, means, and coefficients of variation for DOC, TN, TP, total suspended solids (TSS), chlorophyll‐ a (Chl‐ a ), and near‐surface dissolved oxygen (DO) and temperature.…”