We next quantified site-specific trends for the nitracline (TNO3) and phosphacline (TPO4) depths 20 (Fig. and Table ). This was done to eliminate the possibility that the spatiotemporal variability in sampling induced a spurious trend by over-representing locations with particularly deep nutriclines at later years. The median TNO3 was negative (-0.11 m yr -1 , CI95% = [-0.22, -0.02]) indicating a possible shoaling. In contrast, the median TPO4 shows a greater inclination for phosphacline deepening (0.35 m yr -1 , CI95% = [0.20, 0.49]). Similar with the global regression, this suggests a general deepening of the phosphacline at a rate of 18 m over the past 50 years. Thus, the site-specific trends show that only the phosphacline is deepening, whereas the nitracline is stable or could even be shoaling. = 1 μmol kg -1 and [PO4 3-] = 1/16 μmol kg -1 ) and higher ([NO3 -] = 5 μmol kg -1 and [PO4 3-] = 5/16 μmol kg -1 ) threshold concentrations. Additionally, the global density trends of nutricline depths. See Table for detailed statistics of these observed trends. (C) Regional medians of TNO3 and TPO4. See Table for detailed descriptions of these regions and their respective statistics.