Key Takeaways & Executive Findings
- •• • DGT-measured labile P in upper sediment exceeded overlying water by a significant margin (exact values not provided) from late July to mid-August and in October, confirming sediment as a P source; this temporal pattern is critical for timing remediation efforts to prevent eutrophication. • • P diffusion flux at the sediment-water interface decreased from late July to mid-August and further by October, indicating that aquaculture duration modulates P release; this suggests that early intervention could mitigate P loading. • • Correlation between labile Fe and P, along with bacterial community analysis, implicates Fe-reducing and sulfate-reducing bacteria in P mobilization; this mechanistic insight enables targeted microbial management to reduce P release. • • Bacterial-driven organic P mineralization and inorganic P dissolution were identified as additional P release mechanisms, highlighting the need for integrated approaches addressing both Fe redox and organic matter degradation.
Abstract
This study investigated phosphorus (P) exchange at the sediment-water interface and its microbial driving mechanisms in aquaculture ponds of Chinese mitten crab (Eriocheir sinensis). Using diffusive gradients in thin films (DGT), labile P concentrations in the upper sediment were significantly higher than in overlying water from late July to mid-August and in October, indicating sediment acts as a P source during these periods. The duration of aquaculture was a key factor; P diffusion flux declined from late July to mid-August and further decreased by October. Analyses of labile Fe, P-Fe correlations, and bacterial community composition and function suggested that dissimilatory Fe(III) reduction mediated by Fe-reducing bacteria and chemical Fe(III) reduction driven by sulfate-reducing bacteria metabolites were important mechanisms for P release. Additionally, bacterial-driven organic P mineralization and inorganic P dissolution contributed. The results indicate a high risk of P release from sediment to overlying water from late July to mid-August, potentially significantly affecting water P concentrations. Therefore, controlling sediment P release during this period is crucial.
1. Introduction
Aquaculture ponds of Chinese mitten crab (Eriocheir sinensis) are prone to phosphorus (P) accumulation in sediments, which can become a source of P to overlying water, exacerbating eutrophication. Previous studies have focused on P fractions and release fluxes, but the microbial mechanisms driving P exchange at the sediment-water interface remain poorly understood. This study addresses this gap by employing high-resolution DGT techniques and microbial community analysis to elucidate the role of Fe-reducing and sulfate-reducing bacteria in P mobilization.
The experimental protocol integrates DGT measurements of labile P and Fe with 16S rRNA gene sequencing and functional prediction, providing a comprehensive view of P dynamics. By identifying the key microbial processes and their temporal variability, this research offers actionable insights for pond management to mitigate P release during critical periods. The findings are expected to inform strategies for sediment amendment and microbial regulation to reduce eutrophication risk in crab aquaculture systems.
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XIONG Ruixiang, LIN Jianwei, ZHAN Yanhui, WU Xugan (2026). Phosphorus Exchange Characteristics at the Sediment-Water Interface and Microbial Driving Mechanisms in Aquaculture Ponds of Chinese Mitten Crab (Eriocheir sinensis). Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025042703
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Frequently Asked Questions
What are the specific DGT-measured labile P concentrations in sediment and overlying water during the high-risk period?
The abstract states that labile P in the upper sediment was significantly higher than in overlying water from late July to mid-August and in October, but exact concentrations are not provided in the text. For precise values, refer to the full paper's results section.
How does the P diffusion flux change over the aquaculture season, and what are the quantitative values?
The P diffusion flux showed a downward trend from late July to mid-August and further decreased by October. Exact flux values are not given in the abstract; consult the paper's data for quantitative flux rates.
Which specific bacterial taxa are implicated in Fe reduction and P release?
The abstract mentions Fe-reducing bacteria and sulfate-reducing bacteria as key players, but specific taxa are not listed. The full paper likely provides detailed community analysis, including genera such as Geobacter and Desulfovibrio, based on typical sediment communities.
What are the practical implications for pond management to reduce P release?
The study suggests that controlling P release from sediment is particularly important from late July to mid-August. Management strategies could include reducing organic matter loading, promoting aerobic conditions to inhibit Fe reduction, or applying sediment amendments like iron or aluminum salts to bind P.
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