Invasive floating macrophytes reduce greenhouse gas emissions from a small tropical lake

Abstract

Floating macrophytes, including water hyacinth (Eichhornia crassipes), are dominant invasive organisms in tropical aquatic systems, and they may play an important role in modifying the gas exchange between water and the atmosphere. However, these systems are underrepresented in global datasets of greenhouse gas (GHG) emissions. This study investigated the carbon (C) turnover and GHG emissions from a small (0.6 km2) water-harvesting lake in South India and analysed the effect of floating macrophytes on these emissions. We measured carbon dioxide (CO2) and methane (CH4) emissions with gas chambers in the field as well as water C mineralization rates and physicochemical variables in both the open water and in water within stands of water hyacinths. The CO2 and CH4 emissions from areas covered by water hyacinths were reduced by 57% compared with that of open water. However, the C mineralization rates were not significantly different in the water between the two areas. We conclude that the increased invasion of water hyacinths and other floating macrophytes has the potential to change GHG emissions, a process that might be relevant in regional C budgets.

The Magnitude and Drivers of Methane Ebullition and Diffusion Vary on a Longitudinal Gradient in a Small Freshwater Reservoir

“…For example, we were unable to measure transect-specific nutrient concentrations (e.g., nitrogen and phosphorus), which are known to be positively related to ebullition by stimulating phytoplankton growth (Davidson et al, 2018). We also did not quantitatively measure aquatic plant abundance, which has been 10.1029/2019JG005205 associated with CH 4 ebullition (Marinho et al, 2015) and diffusion (Attermeyer et al, 2016), though we note qualitatively that plant abundance at our transect sites was minimal. Diffusion was also likely underestimated because we assumed that diffusive rates were the same over a diel period when scaled from the short duration of time that we measured efflux.…”

Large but variable methane production in anoxic freshwater sediment upon addition of allochthonous and autochthonous organic matter

“…This could have consequences for lake and reservoir management, and needs to be further explored. For a more comprehensive view of the effect of different aquatic vegetation types on greenhouse gas emissions, other processes than OC decomposition would need to be taken into account such as primary productivity, the quantity of substrates provided to methanogens (Whiting and Chanton ), or CH 4 rhizospheric oxidation (Ribaudo et al ; Attermeyer et al ). Furthermore, other factors than the type of OC might act on CH 4 production in freshwater sediments, such as the sediment content in electron acceptors, and temperature, and should be investigated to better understand and predict CH 4 production in freshwaters.…”

“…In addition, CH 4 production is strongly dependent on temperature (Bastviken 2009;Yvon-Durocher et al 2014), such that tropical freshwaters may be particularly strong CH 4 sources (Tranvik et al 2009;Bastviken et al 2010). Tropical hydropower reservoirs have been pointed as strong anthropogenic CH 4 sources (Barros et al 2011), which is of imminent concern given the current boom in hydropower construction in many tropical countries (Zarfl et al 2015). Therefore, an important question in the context of climate change as well as sustainable energy production is to understand how CH 4 production is regulated in anoxic sediments of lakes and reservoirs.…”

Global Estimation of Biophysical Variables from Google Earth Engine Platform

“…The GEE data catalogue contains numerous remote sensing data sets such as top and bottom of atmosphere reflectance, as well as atmospheric and meteorological data. Data processing is performed in a parallel on Google's computational infrastructure, dramatically improving processing efficiency, and opens up excellent prospects especially for multitemporal and global studies that include vegetation, temperature, carbon exchange, and hydrological processes [31][32][33][34][35].…”