Long-term effects of dead algal deposition on sediment surfaces: Behavior of endogenous phosphorus release in sediments

• Published in: Water research (Oxford) 2025-01, Vol.268 (Pt B), p.122742, Article 122742
• Main Authors: Chen, Yanqi, Li, Dapeng, Liu, Songqi, Zhang, Yujie, Yan, Xinrui, Song, Xinyu, Li, Ziyu, Li, Boling, Shan, Sujie, Zhu, Yizhi, Hou, Jun
• Format: Article
• Language: English
• Subjects: Algae; Algae bloom; Aquatic trophic level; Eutrophic lake; Eutrophication; Geologic Sediments - chemistry; Lakes; Phosphorus; Phosphorus cycle
• ISSN: 0043-1354; 1879-2448; 1879-2448
• DOI: 10.1016/j.watres.2024.122742

•Long-term effects of dead algal deposition on endogenous P release were explored•Responses of PAOs in sediments on dead algal deposition were investigated•Both microenvironmental and microbial changes driven the endogenous P release•Release of P from sediments reached maximum on 40 day (0.14±0.017 mg L-1 in Amend12)•Algae should be harvested at bloom peak to prevent priming effects of deposited algae Algae blooms are frequently triggered owing to the improvements in aquatic trophic levels. The aggregated algae from these blooms are eventually dead and accumulate on sediment surfaces, impacting the microenvironment and phosphorus cycling in aquatic systems. However, research on the effects of naturally dead algal deposition on endogenous P release from sediments is lacking. In this study, we investigated the long-term effects of dead algal deposition at varying concentrations on P release from sediments and the underlying mechanisms by assessing microbial metabolism and community structure. The results showed that following the dead algal deposition, the release of P from sediments to the water column peaked on day 40 (0.14±0.017 mg L-1 in Amend12) and the SRP exchange capacity reached maximum (6.09 ± 1.63 mg/(cm2·d) in Amend12) at sediment-water interface in phase1 (0–3 day). This might be primarily attributed to the deposition of dead algae introducing much organic matter (such as organic carbon and organic phosphorus), thus altering the sediment microenvironment, which increased the activity of phosphorus-cycle microorganisms, such as polyphosphate-accumulating organisms, through increasing C source metabolism, reducing intracellular ammonia inhibition, and creating more suitable anaerobic conditions. Therefore, this study has improved our understanding of the management strategies for controlling endogenous phosphorus release in eutrophic shallow lakes, suggesting that the priming effects of freshly deposited algae could be mitigated by harvesting algae at the peak of blooms. [Display omitted]