A quantitative analysis of the phytoplankton of the Gulf of Panama III. General ecological conditions and the phytoplankton dynamics at 8°45'N, 79°23'W from November 1954 to May 1957

Bi-weekly phytoplankton samples were collected at 0, 10, and 20 m and enumerated by the Utermöhl sedimentation technique; 14C productivity measurements at 10 m, oblique zooplankton tows, and routine hydrographic observations were also made. Northerly winds induce upwelling during December-April, followed by a rainy season; a slight resurgence in upwelling may occur during July and/or August. Annual variations in upwelling intensity and rainfall occur. During upwelling, the upper 50 m, about 30 per cent of the total volume of the Gulf of Panama, is replaced with water 5 to 10 C colder than the more stratified, turbid and nutrient impoverished watermass present during the rainy season. The mean annual runoff accompanying an average annual precipitation of 2731 mm is estimated to equal a layer of fresh water 3.2 m thick. About 10 per cent of the phytoplankton phosphate and inorganic nitrogen requirements during the rainy season are accreted. (PDF contains 260 pages.)