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Study of the degradability of Phaeocystis mucus carbohydrates by heterotrophic bacteria is discussed. The study used partially purified mucus as a substrate in oxic and anoxic enrichments of marine bacteria. The degradable of the important part of the biomass of the organism is of help for understanding impact of Phaeocystis blooms on the marine carbon cycle. Breakdown of the mucopolysaccharides, during which the carbohydrate composition of the residual fraction did not change, slowed greatly after about 15 days. Incomplete degradation was the result of release of inhibitors produced during breakdown.

A biochemical analysis was conducted to determine which components of the photosynthetically produced dissolved organic matter (PDOC) derived from phytoplankton are important for pelagic heterotrophic bacteria. Experiments were conducted in three temperate lakes at different times in the phytoplankton growing season using radioactive carbon tracing methods. The results showed that the size distribution and biochemical composition of PDOC released from phytoplankton vary greatly both between lakes and over time within lakes. Heterotrophic bacteria respond by seasonal variation in their efficiency to utilize various types of substrates.