Estoque de carbono em viveiros aquícolas: evidências em 125 viveiros escavados em Minas Gerais, Brasil

Abstract

Population growth and rising income in low- and middle-income countries have led to a significant increase in the demand for protein and other animal-derived products. The rapid expansion of aquaculture to meet this demand has generated interest in its potential to reduce environmental impacts. Among production systems, earthen ponds are among the most widely used worldwide and have the potential to mitigate greenhouse gas (GHG) emissions through the accumulation of organic carbon in their sediments. Despite this, they remain an underexplored opportunity for carbon capture, with limited data on the local factors influencing their efficiency. In this study, we investigated organic carbon stocks in the sediments of 125 earthen ponds in Minas Gerais, Brazil. Abiotic variables and farm identity (random effect) were more strongly associated with carbon than the structure of the cultured community, represented by the species composition and the type of production system, classified into native monoculture, tilapia monoculture, polyculture with tilapia, and native polyculture. Although polyculture systems showed higher organic carbon stocks descriptively, this pattern was associated with the greater longevity of these systems rather than an intrinsic advantage of polyculture. Cold-water ponds, in contrast, exhibited significantly lower organic carbon stocks, a pattern associated with higher water exchange rates. The total carbon stock in earthen ponds in Minas Gerais was estimated at 94.7 Gg C (95% CI: 75.1–117.0 Gg C), with a mean concentration of 25.3 t C ha⁻¹. The median annual carbon burial rate was 2.5 t C ha⁻¹ yr⁻¹ (95% CI: 1.9–3.2 t C ha⁻¹ yr⁻¹), calculated based on a weighted mean pond age of 10.2 years (95% CI: 8.6–11.9 years). Carbon concentration varied across the study region, with a threefold difference between the lowest and highest median values (1.8 to 6.4 kg C m⁻²), indicating strong spatial heterogeneity. The results indicate that the temporal and operational continuity of ponds is a key factor for carbon sequestration, suggesting that strategies aimed at stabilizing carbon after sediment removal are essential to ensure its long-term sequestration.