Similar Relationships Between Pelagic Primary and Bacterial Production in Clearwater and Humic Lakes

We examined the relationship between planktonic primary production (PP) and bacterial production (BP) in 16 subarctic lakes along an altitude gradient extending from colored coniferous forest lakes to clearwater high alpine lakes. We tested the hypothesis that there was a shift from low to high PP:BP ratios along this gradient. The clearwater alpine lakes had low PP:BP ratios, generally well below 1.0, while the highest ratios were found in the forest lakes. In contradiction to our hypothesis, the pelagic systems of the clearwater lakes were thus dominated by bacterial energy mobilization from external carbon sources. In this respect the alpine lakes were similar to highly humic lakes. We suggest that the relationship between C, N, and P plays a critical role in determining the PP:BP ratio, and that the N:P ratio in particular can be critical for development of PP or BP dominance in the pelagic systems of unproductive lakes.