Knowing your limits: Patterns and drivers of nutrient limitation and nutrient–chlorophyll relationships in US lakes

Although understanding nutrient limitation of primary productivity in lakes is among the oldest research priorities in limnology, there have been few broad-scale studies of the characteristics of phosphorus (P)-, nitrogen (N)-, and co-limited lakes and their environmental context. By analyzing 3342 US lakes with concurrent P, N, and chlorophyll a (Chl a) samples, we showed that US lakes are predominantly co-limited (43%) or P-limited (41%). Majorities of lakes were P-limited in the Northeast, Upper Midwest, and Southeast, and co-limitation was most prevalent in the interior and western United States. N-limitation (16%) was more prevalent than P-limitation in the Great Basin and Central Plains. Nutrient limitation was related to lake, watershed, and regional variables, including Chl a concentration, watershed soil, and wet nitrate deposition. N and P concentrations interactively affected nutrient–chlorophyll relationships, which differed by nutrient limitation. Our study demonstrates the value of considering P, N, and environmental context in nutrient limitation and nutrient–chlorophyll relationships.