Transformation and Decomposition of Photosynthetic Products of Lake Phytoplankton

Abstract

Decomposition and transformation processes of cellular and extracellular products of lake phytoplankton photosynthesis were determined using a ¹⁴C tracer technique under laboratory conditions. The cellular organic matter was consumed by phytoplankton respiration in the early stage of incubation and decreased to 19% of the initial amount for 30 days at 25°C. A shift occurred in the chemical constitution of the predominant cellular organic matter : hot ethanol soluble and hot water soluble components changed into hat water insoluble ones. After decomposition for 85 days, 14.7% and 1.5% of the cellular products were transformed to particulate and dissolved organic matter, respectively. The extracellular products, which were 9.3% of the total photosynthetic products, were easily metabolized and decomposed by lake bacteria. After 133 days, 19.4% and 7.5% of the initial extracellular products changed to particulate and dissolved organic matter, respectively. During the course of the decomposition, a marked difference was observed in gel filtration profile of the dissolved organic matter derived from the extracellular products.