Historical and projected trends of long-term nitrogen dynamics from China's mariculture.

Abstract

Mariculture sustains global food security yet generates substantial nitrogen waste through uneaten feed and metabolic excretion, with poorly quantified long-term fluxes. We assessed nitrogen dynamics of China's mariculture from 1983 to 2024 and projected future trends under 12 scenarios. Here we show that nitrogen discharge surged 150-fold to 93.73-128.37 kilotons in 2024, driven by fed species. Concurrently, nitrogen removal by shellfish and seaweed rose from 5.06-8.80 kilotons to 89.03-137.68 kilotons. Spatially, southern provinces emerge as dominant discharge hotspots, whereas northern provinces demonstrate strengthened sink potential. Scenario analyses reveal a critical tipping point: although currently a net sink at -9.36 kilotons, the sector risks reverting to a net source by 2030 under most trajectories, potentially peaking at 15.14 kilotons. Strategic interventions, including expanding cultivation areas and increasing density for both fed and extractive species, could expand net removal to 100.47 and 245.71 kilotons by 2060 and 2100, respectively.