The distribution characteristics, concentration dynamics, and organic matter (OM) interactions of different phosphorus (P) species in lake sediments are fundamental to understanding P cycling and release mechanisms. This study investigated P speciation, concentrations, and their associations with OM in the sediments and pore water of Lake Dian, with a focus on spatial heterogeneity and centennial-scale evolution. Results showed that sedimentary P was predominantly retained in relatively stable fractions, namely NaOH-rP, HCl-P, and Res P. Pore-water dissolved organic matter (DOM) was dominated by authigenic, protein-like components, whereas sedimentary OM originated from mixed sources, including aquatic macrophytes, algae, and sewage inputs. Centennial sediment records indicated that increases in P and OM concentrations coincide with the intensification of watershed anthropogenic activities. The spatial co-distribution of OM and P suggested that OM enhanced internal P mobilization by regulating redox conditions and promoting the transformation of labile P fractions (e.g., BD-P). The sediment–water P cycle was governed by coupled physical transport and OM-driven biogeochemical processes. Notably, the degradation of algal-derived OM was identified as a key driver of internal P loading, as it stimulated microbial activity and oxygen consumption, thereby facilitating P release. These findings indicate that effective lake management should integrate external nutrient load reduction with strategies targeting OM-mediated internal P cycling to achieve sustainable water quality improvement in Lake Dian.
Li et al. (Sat,) studied this question.