福建省山仔水库碳磷比生态计量特征研究OA

[Objective]Eutrophication-induced cyanobacterial blooms have posed a severe threat to water qual-ity and ecosystem stability.This study aims to investigate the spatiotemporal distribution characteristics of the dissolved inorganic carbon-to-total phosphorus ratio(DIC/TP)and its effects on the phytoplankton community structure in reservoirs,and to evaluate the sensitivity of DIC/TP as an early-warning indicator for eutrophica-tion.[Methods]From April 2023 to February 2024,water samples and phytoplankton samples were collected at 5 sampling sites(reservoir center,dam front,Rixi inlet,Huangdi Cave,and river channel)in Shanzai Reser-voir.Hydrological and physicochemical indicators,and concentrations of DIC,dissolved organic carbon(DOC)and TP were measured.Analysis of variance(ANOVA)and correlation analysis were performed to explore the correlations among these indicators.[Results]A total of 6 phyla and 51 genera of phytoplankton were identi-fied during the study period.The total phytoplankton density ranged from 1.90×106 to 2.71×108 cells·L−1,exhib-iting a seasonal variation pattern of spring>summer>autumn>winter.The DIC/TP ratio varied from 12.0 to 825.4,with an average value of 178.9,and showed significant spatiotemporal differences.Its seasonal variation followed the order of winter>autumn>summer>spring,while the spatial variation was in the sequence of reser-voir center>dam front>Rixi inlet>Huangdi Cave>river channel.Correlation analysis revealed that the DIC/TP ratio was extremely significantly negatively correlated with total phytoplankton density(r=−0.440)and cy-anobacterial density(r=−0.480),whereas extremely significantly positively correlated with diatom density(all P<0.001).Additionally,the ratio was also significantly correlated with the trophic state index and environmental factors such as water temperature(WT)and Secchi disk depth(SD)(P<0.05).[Conclusion]The DIC/TP ratio is a key factor regulating the phytoplankton community structure.Low DIC/TP ratios in spring and summer are associated with high cyanobacterial bloom risks,while high ratios in winter favor the dominance of chloro-phytes and diatoms.An increase in the DIC/TP ratio can drive the phytoplankton community to shift from cy-anobacteria-dominated to chlorophyta-and bacillariophyta-dominated.Compared with the nitrogen-to-phos-phorus ratio(TN/TP),the DIC/TP ratio responds more sensitively to eutrophication status,making it a valuable early-warning indicator for reservoir eutrophication.This study deepens the understanding of the effects of the DIC/TP ratio on phytoplankton community structure in reservoirs,providing a new theoretical perspective and practical reference for the restoration of eutrophic water bodies.