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The Upper Limit of Phytoplankton Production as a Function of Nutrient Load, Temperature, Retention Time of the Water, and Euphotic Zone Depth
Author(s) -
Uhlmann Dietrich
Publication year - 1978
Publication title -
internationale revue der gesamten hydrobiologie und hydrographie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 0020-9309
DOI - 10.1002/iroh.19780630305
Subject(s) - photic zone , phytoplankton , nutrient , residence time (fluid dynamics) , environmental science , outflow , zoology , biomass (ecology) , inflow , hydrology (agriculture) , ecology , oceanography , biology , geology , geotechnical engineering
In laboratory models of sewage ponds operated on a semicontinuous‐flow basis, the net primary production II of the phytoplankton was measured by harvesting the suspended matter both from the outflow and the bottom of the vessels at daily intervals. The maximum value of II was as high as 50 mg dry weight/l day (corresponding to 20 mg C/l day). With the nutrient load L kept ad a constant level, the steady state phytoplankton biomass x decreased with decreasing water residence time t in accordance with the dropping inflow concentration of the nutrients. On the other hand, at 20 °C no higher x was yielded at t =40 than at t =5 days. This result obviously has to be attributed to a substantial increase in grazing rate with progressing t at the temperature level of 20 and 30 °C. In this connection extremely low magnitudes of II may result despite optimum levels of nutrient supply, radiation and temperature. The highest estimates of II hitherto measured and recorded in the literature relate to the euphotic zone depth ( z eu in m) as follows: