Relationship between primary productivity (C¹⁴ method) and phytoplankton in a mesotrophic lake

The relationships between primary productivity and phytoplankton numbers and volume were studied in a small mesotrophic lake near College Station, Texas, between April 1966 to February 1967. Each of four seasonal experiments was a Latin square with combinations of 20, 10, and 0 pounds of nitrogen and phosphate per surface acre replicated three times. Potassium was constant at 5 pounds per acre, and two cells of the design (0:10:5 and 10:0:5, NPK) were empty. Treatments thus numbered seven, including the control (0:0:5). Three blanks (0:0:0) permitted the evaluation of potassium. Experiments were run in 24 four-foot-diameter, open-bottom polyethylene tubes transecting the lake from top to bottom. Primary productivity of phytoplankters was estimated by the C-14 technique; numbers were determined with a counting chamber. ..