Low carbon dioxide emissions from aquaculture farm of lake revealed by long-term measurements

Abstract

Fast-growing global aquaculture has resulted in eco-environmental costs, one of the key concerns is carbon emissions. Freshwater lakes have been long used for aquaculture, and CO2 emissions from the system should be assessed to better understand the role of aquaculture in carbon budget. Here, CO2 emissions from aquaculture farm and open water of a lake in eastern China were investigated with long-term (2000–2017) field samplings. Positive correlation between annual CO2 emissions and dissolved organic carbon (R2 = 0.63, p < 0.01) occurred at aquaculture farm, suggesting feed-derived carbon application contributed to aquaculture CO2 emissions. But unexpected lower CO2 emissions (8.01 ± 5.28 mmol m−2 d−1) occurred at aquaculture farm compared with emissions from open water (11.58 ± 7.42 mmol m−2 d−1). Although temporal variation of CO2 emissions was negatively correlated with chlorophyll-a at non-aquaculture region, a reciprocal relationship with dissolved oxygen level (R2 = 0.35, p < 0.01) was found at aquaculture farm, which was attributed to the presence of aquatic vegetation used for the aquaculture. Meanwhile, positive correlation between annual CO2 emissions and nutrient was found, and aquatic vegetation planting in the aquaculture may reduce the CO2 emissions via direct photosynthesis and indirect ways of such as absorbing nutrient. The findings suggested that the two aquaculture management actions (feed addition and vegetation planting) are two antagonistic processes in the CO2 emissions, likely lead to the aquaculture farm as relatively low CO2 source. Our results may provide an informed solution for the tradeoff between CO2 emissions and aquaculture production.