Sampling site,Mean 'old' sample,Mean 'new' sample,p-value (Wilcoxon rank sum test) C1-2012-Apr,0.27,0.239,0.002 C12-2012-Oct,0.259,0.209,<0.001 N1-2012-Oct,0.278,0.236,0.002 N1-2012-Nov,0.271,0.259,0.218 N6-2012-Apr,0.289,0.256,0.017 N6-2012-Jun,0.259,0.252,0.357