Eigenvalues, cumulative percent variation (Cum. %), and eigenvectors of a PCA examining sediment variables.

Data were obtained at 41 and 63 stations in 1997 and 2011, respectively. TN: total nitrogen; TOC: total organic carbon; δ¹⁵N: stable nitrogen isotope ratio; δ¹³C: stable carbon isotope ratio; Eh: redox potential; AViS: acid-volatile insoluble sulfide.

**p < 0.01

***p < 0.001

Eigenvalues, cumulative percent variation (Cum. %), and eigenvectors of a PCA examining sediment variables.