Phytoplankton productivity in turbid waters

Many of the freshwater areas in the world are turbid, due to suspended inorganic particles. The euphotic depth of the shallow turbid impoundment, Wuras Dam, varies between 0.3–1.3 m. This results in a compressed production profile where accurate measurements become difficult. Tubes of various lengths have been used and usually render higher rates, when compared to discrete bottle incubations. A tube the depth of the euphotic zone confines the phytoplankton in the light and the rates measured represent the maximal possible under the prevailing conditions. Longer tubes include an aphotic portion and give an idea of the magnitude of respiration losses. The depth of the mixing layer appears to be especially important in turbid systems as the time spent in the dark, relative to the light is of great importance and may be the most important regulating factor in such waters.