Multi-source DOM inputs dictate net extra carbon mineralization in eutrophic lakes via non-linear co-metabolism effects

DOM from aquatic plants and rainwater induced positive co-metabolism effects, while sewage-derived DOM induced negative effects in algal-rich Lake Taihu incubations.

• Why it matters: In eutrophic lakes, added dissolved organic matter can reshape decomposition of resident DOM, but the joint roles of DOM source and loading level in bloom-affected waters remain unclear.
• What they did: Incubations used algal-rich Lake Taihu water with separately added DOM from rainwater, aquatic plant leaves, terrestrial litter, and treated sewage effluent at matched carbon-addition levels, linking co-metabolism effects to DOM optical and chemistry traits.
• The result: Co-metabolism effects varied nonlinearly with addition level, peaking at intermediate concentrations, and source-resolved scenario analysis suggested sewage-derived negative contributions could offset much of natural-source positives, with a potential net increase in carbon mineralization.

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