Factors controlling phytoplankton primary productivity in Byram Lake,Mt. Kisco,N.Y., summer 1977

Phytoplankton productivity was measured in Byram Lake Reservoir during summer 1977. Depth integrated productivity (0–5 gC m^{– 2} d^–1) increased with station depth, which together with visibility measurements indicated that light did not limit deep station productivity (C1 and S2). Macrophytes at station C5 (shallow) reduced the euphotic zone to 0 in June.On a unit depth basis, C5 was the most productive station. Apparently changes in macrophyte growth, regulated by light and temperature, controlled phytoplankton production. At C1, productivity was related to levels of different nutrients at different depths, the thermocline influencing nutrient availability at mid-depth. At S2, NH₃-N controlled mid-depth productivity. Surface and mid-depth productivity appeared influenced by factors not measured in this study.