We tested the significance of nutricline trends using two independent methods. First, we fitted linear regression models to average nutricline depths through time. These nutricline depths were annual averages for each unique geographic coordinate. Two separate regressions were fitted to nitracline and phosphaclines, and an F-test determined if each regression was significant (i.e., p < 0.05). Second, we analyzed each geographic coordinate that had average nutricline depths recorded for two or more unique years. For each coordinate, we fitted a regression to its average nutricline depths vs. years to quantify its site-specific trend. These site-specific trends were quantified separately for nitraclines and phosphaclines. The sign test determined if the global median sitespecific trend was significantly different from zero. Additionally, the Kruskal-Wallis test determined if the median trends of nitracline and phosphaclines were significantly different from each other. We also calculated 95% confidence intervals (CI95%) for the median trends by generating 10,000 bootstrap samples of the data set. Thus, with global regressions and site-specific trends, we were able to test if nitracline and phosphacline depths were generally shifting in recent decades.