17 AUG 2026 (MON) 15:35 - 16:05

Greenhouse Gas Dynamics of Aquaculture Ponds in (Sub)tropical Southern China

Miss YANG Qianqian 

( Supervisor: Prof Lishan Ran )

Abstract:

Aquaculture ponds, among the fastest-growing inland water bodies, are hotspots of greenhouse gas (GHG) emissions, particularly CO2 and CH4. However, aquaculture ponds are strongly disturbed by human activities, and their carbon emissions exhibit significant variability under different aquaculture types and temporal scales. Such variability complicates carbon flux quantification and makes the mechanisms driving CO2 and CH4 production poorly understood. Therefore, to investigate the dynamics of GHG emissions from subtropical aquaculture ponds, we selected 22 ponds across Guangdong Province and Hong Kong SAR and conducted measurements at multiple spatial and temporal scales.

Under different management practices, the main drivers of carbon emissions were different. In the pond with low artificial disturbance and increased ecosystem stability (P1), climatic factors were the dominant controls on carbon emissions. In the more intensively managed pond (P2), however, the effects of human activities tended to override those of meteorological factors. In particular, the draining-drying-refilling practice disrupted the original aquatic environment and promoted the decomposition of sediment organic matter, thereby substantially reducing CH4 emissions. As a result, the total CO2-equivalent emission flux from P2 was approximately 62% lower than that from P1.

Substantial CH4 emissions were observed from (sub)tropical aquaculture ponds, with significant variations among pond types. Fish ponds exhibited the highest FCH4 (226 ± 441 mg m–2 d–1), followed by shrimp ponds (68 ± 159 mg m–2 d–1) and crab ponds (49 ± 112 mg m–2 d–1). Ebullition was the dominant pathway of CH4 emissions, accounting for over 70% of the total CH4 flux. CH4 emissions were collectively regulated by management practices, environmental variables, and methane-cycling microbial communities. Salinity suppressed FCH4 by inhibiting methanogen metabolism and restructuring methanogenic community, while elevated organic substrates could offset the salinity-driven inhibitory effect. Furthermore, rising temperature could substantially stimulate CH4 emissions, especially ebullition, with an 11% increase in FCH4 per 1 °C rise in water temperature. This thermal sensitivity of FCH4 was further amplified in ponds with higher organic substrates, revealing a synergistic effect between temperature and substrate availability in promoting CH4 production.

At the diel scale, CO2 emissions from aquaculture ponds exhibited stronger diel dynamics than CH4 emissions. In general, CO2 fluxes peaked around sunrise and declined to their lowest levels between 14:00 and 18:00. Therefore, sampling restricted to daytime would lead to a substantial underestimation of FCO2 by approximately 10%, while sampling concentrated between 14:00 and 18:00 could result in an underestimation of up to 53%. The diel variation in CO2 fluxes reflects the dynamic balance between aquatic respiration and photosynthetic uptake, whereas CH4 fluxes are mainly controlled by sediment-related anaerobic metabolism.

Overall, these findings demonstrate that (sub)tropical aquaculture ponds are important yet highly heterogeneous sources of GHG emissions. Carbon emissions varied substantially across pond types, management practices, and temporal scales, highlighting the need to account for both anthropogenic disturbance and environmental controls in flux estimation. This study provides a framework for scaling the contribution of aquaculture ponds to the global CO2 and CH4 budgets.