BACTERIOPLANKTON

BACTERIOPLANKTON, a term sometimes used to denote the bacterial part of the bioseston. B. in size approaches the nanoplankton (see Plankton). The number of bacterial forms found in B. is very large, but to isolate from them with full certainty forms specifically characteristic of the water, and to separate them from accidental forms, due to the poor study of B., with few exceptions, has not yet been possible. Of the 42 forms of bacteria found by Bolokhtsev and Grimm in the waters of Lake Ladoga, the most common were Micr. candicans, Bac. aquaticus communis, Sarcina lutea and Bac. fluorescens liquefaciens. There are no exact data on the absolute content of B. in different waters. According to data obtained by the colony count method, for the open ocean there are figures of about 1,000 in 1 cubic cm; in the littoral zone (see Saprobic zones), the figures increase and show greater fluctuations, with depth they fall, but B. is also found at very great depths. The greatest fluctuations are found in rivers. Bacterioplankton usually increases very significantly with the pollution of water by easily decomposable organic substances (for rivers, for example, it can rise from hundreds of bacteria to tens of millions in 1 cubic cm).