Better assessments of greenhouse gas emissions from global fish ponds needed to adequately evaluate aquaculture footprint

Spatial and temporal variability of methane emissions and environmental conditions in a hyper-eutrophic fishpond

“…Our results agree with the generally accepted view that processes other than diffusive fluxesmost likely ebullitionrepresent the major CH4 pathway to the atmosphere in hyper-eutrophic ponds (Kosten et al, 2020).…”

“…Most concerning are CH4 emissions as freshwater aquaculture systems release more than 6 Tg CH4 yr -1 (Yuan et al, 2019). Methane can be emitted via several pathways: simple molecular diffusion, ebullition (in the form of bubbles released from oversaturated sediments), plant-mediated flux (Bastviken et al, 2004), but also through so far neglected pathways including aeration, emissions from dry/drying sediments, or dredged organic material (Kosten et al, 2020). Among all, ebullition is considered the dominant pathway (van Bergen et al, 2019;Kosten et al, 2020), which can contribute 50-96 % (Casper et al, 2000;Xiao et al, 2017;van Bergen et al, 2019;Yang et al, 2020;Zhao et al, 2021) to the total CH4 flux.…”

“…Methane can be emitted via several pathways: simple molecular diffusion, ebullition (in the form of bubbles released from oversaturated sediments), plant-mediated flux (Bastviken et al, 2004), but also through so far neglected pathways including aeration, emissions from dry/drying sediments, or dredged organic material (Kosten et al, 2020). Among all, ebullition is considered the dominant pathway (van Bergen et al, 2019;Kosten et al, 2020), which can contribute 50-96 % (Casper et al, 2000;Xiao et al, 2017;van Bergen et al, 2019;Yang et al, 2020;Zhao et al, 2021) to the total CH4 flux. Along with the second important pathwaymolecular diffusion, both exhibit high spatiotemporal variability due to various physical and biological factors acting on very short time scales, for instance, temperature (van Bergen et al, 2019), eutrophication (Zhang et al, 2021), water depth (DelSontro et al, 2016), CH4 production rates (Zhou et al, 2019), CH4 oxidation rates (Sanseverino et al, 2013), dissolved oxygen concentration (Xiao et al, 2017), management regime (Yang et al, 2019), or the quality of organic matter in the sediment (Schmiedeskamp et al, 2021).…”

Impacts of Coastal Shrimp Ponds on Saltwater Intrusion and Submarine Groundwater Discharge

“…These high concentrations mean that hotspots of lateral carbon and nitrogen fluxes may be generated by SGD originating from shrimp farms, even though SGD volumes from aquaculture are generally lower than from sandy beaches (Geng et al, 2021;Taniguchi et al, 2019).The diverse feeding activities (Darodes de Tailly et al, 2021) are the primary control of nutrient loadings and carbon cycling, especially as aquaculture footprints are increasing. Because of this intensive carbon and nitrogen loading, aquaculture systems have the potential to become major anthropogenic sources of CH 4 and N 2 O emissions (Kosten et al, 2020;Yuan et al, 2019). Additionally, shrimp aquaculture can introduce pollution into soils and aquifers due to, for example, the bioaccumulation of heavy metals (Luo et al, 2021;Tang et al, 2020) and use of antibiotics (Zhou et al, 2020) in the ponds.…”

Impacts of surface water interchange between urban rivers and fish ponds in Chu river of Nanjing, China: A potential cause of greenhouse gas emissions

“…The immoderate usage of aqua feeds and the production of agricultural wastes enhance freshwater eutrophication and the deposition of organic carbon (OC) in fish ponds (Bohnes et al, 2019). In addition to that, benthic sediments of the pond are excellent for the anaerobic decomposition of organic matter (OM) due to the low water velocity, thus many previous studies demonstrated that freshwater aquaculture ponds emit higher GHGs than urban water bodies (Kosten et al, 2020). For example, Nanjing, a major city in China, is located in a subtropical monsoon climatic zone with a large number of urban rivers and a sizable freshwater aquaculture industry (Cheng and Hu, 2012).…”