The Adaptation of Plankton Algae III. With Special Consideration of the Importance in Nature.

A survey of the adaptation of plankton algae in Nature to different light intensities and temperatures is given. The adaptation is always important for the plankton populations at all depths. However, the shade adaptation of the algae in the lower part of the photic zone is often of relatively little importance for the integral primary production per unit of surface, except on the by no means rare occasions when the hulk of the algae is found in this lower part. It is shown that the I_k of surface plankton during summer in the Arctic is high despite the low temperatures present. This is due to an increase of the enzyme quantities per cell. Daily fluctuations in I_k are due partly to photooxidation, partly to the fact that the periods for the production of chlorophyll and photosynthetic enzymes are mutually displaced. Despite the daily fluctuations in I_k the difference between "sun" phytoplankton and "shade" phytoplankton is distinct. [ABSTRACT FROM AUTHOR]