Decomposition of Lake Phytoplankton. 1. Dynamics of Short-Term Decomposition

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Abstract
Short-time (24 h) and long-time (4-6 d) decomposition of phytoplankton cells were investigated under in situ conditions in four Danish lakes. Carbon-14-labelled, dead algae were expsoed to sterile or natural lake water and the dynamics of cell lysis and bacterial utilization of the leached products were followed. The lysis process was dominated by an initial fast water extraction. Within 2 to 4 h from 4 to 34% of the labelled carbon leached from the algal cells. After 24 h from 11 to 43% of the initial participate carbon was found as dissolved carbon in the experiments with sterile lake water; after 4 to 6 d the leaching was from 67 to 78% of the initial 14C. The leached compounds were utilized by bacteria. A comparison of the incubations using sterile and natural water showed that a mean of 71% of the lysis products was metabolized by microorganisms within 24 h. In two experiments the uptake rate equalled the leaching rate.