MICROGRAZER IMPACT AND SUBSTRATE LIMITATION OF BACTERIOPLANKTON IN LAKE-MICHIGAN

Bacterial growth rates were always enhanced by organic substrate additions indicating that bacterial growth is limited, to some degree, by substrate availability. The authors obtained loss rates and intrinsic growth rates each between 0.32-1.45 d-1. Grazers were predominantly picoplankton-size organisms, presumably heterotrophic flagellates. Only 2-3% of bacterial cells were incorporated into larger size fractions after 24h. Heterotrophic bacteria were not a direct, significant, carbon source for the upper trophic levels. -from Authors