In the quest to meet the world’s growing demand for aquatic food, aquaculture has emerged as a critical player. Yet, the environmental impact of these practices remains a topic of intense scrutiny. A recent study published in the journal *Aquaculture Reports* (translated from Chinese as “水产养殖报告”) sheds light on the carbon budgets and greenhouse gas (GHG) emissions from monoculture ponds, offering valuable insights for the energy and aquaculture sectors.
Led by Zhao-Jun Yong from the Department of Life Sciences at National Chung Hsing University in Taiwan, the research constructed carbon budgets and determined GHG emissions from ponds cultivating Taiwanese hard clams (Meretrix taiwanica) and milkfish (Chanos chanos). The findings reveal a stark contrast between the two systems, with significant implications for sustainable aquaculture practices and carbon management.
Phytoplankton production was identified as the primary carbon input pathway in both clam and fish ponds. However, the study found that respiration offset most of this carbon in fish ponds, turning them into heterotrophic systems that emitted an average of 0.21 grams of carbon per square meter per day. In contrast, clam ponds remained autotrophic, functioning as carbon sinks with an average uptake of 0.06 grams of carbon per square meter per day, even when accounting for CO2 release by biocalcification.
“The accumulated sediment significantly contributed to the carbon output pathways in the ponds,” explained Yong. “In clam ponds, it accounted for 62–77% of the carbon output, while in fish ponds, it was 23–52%.” The study suggests that an unaccounted pathway of carbon input likely contributed to sediment accumulation in clam ponds, possibly due to the filter-feeding behavior of clams, which induces resuspension or the production of pseudofeces. In fish ponds, feed input was the main contributor to sediment accumulation.
The research also examined GHG emissions, finding that methane fluxes contributed relatively little to the overall emissions from both ponds. However, nitrous oxide fluxes could significantly alter the fish ponds into greater GHG sources. Based on the 100-year global warming potential (GWP100), GHG emissions during the culture period were 0.46 ± 0.75 grams CO2e m−2 d−1 in clam ponds and 1.15 ± 1.15 grams CO2e m−2 d−1 in fish ponds.
These findings have profound implications for the aquaculture industry and the broader energy sector. As the world seeks to balance food production with environmental sustainability, understanding the carbon dynamics of different aquaculture systems becomes crucial. The study highlights the potential of clam ponds as carbon sinks, offering a promising avenue for carbon offset initiatives.
Moreover, the research underscores the need for targeted strategies to mitigate GHG emissions in fish ponds. By optimizing feed inputs and managing sediment accumulation, aquaculture practitioners can reduce the environmental footprint of their operations. This not only benefits the planet but also enhances the long-term viability of the industry.
As Zhao-Jun Yong and his team continue to explore the intricacies of carbon fluxes in aquaculture, their work paves the way for more sustainable and efficient practices. The insights gained from this study are set to shape future developments in the field, guiding stakeholders towards a more balanced and environmentally conscious approach to aquaculture.