PCA plot based on nine normalized sediment variables in 1997 (<i>n</i> = 41) and 2011 (<i>n</i> = 63).

<p>The first two principal components (PC1 and PC2) accounted for 59.4% and 20.3% of total variance, respectively. Arrows indicate correlations between environmental variables and each PC axis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135125#pone.0135125.t002" target="_blank">Table 2</a>).