Structure, diversity, and catabolic potentialities of aerobic heterotrophic bacterial populations associated with continuous cultures of natural marine phytoplankton

Abstract

Variations of structure (probable taxonomic generic groups; ecological profiles), diversity (Shannon index, ¯H), and average catabolic potentialities (strain's average exoenzyme equipment, EAI; average carbonaceous compound utilization, UAI) of bacterial populations during two experimental phytoplankton blooms are described and show a certain overall unity. Oligotrophic conditions are characterized by high diversity levels (¯H from 3.60 to 4) and moderate catabolic potentialities (EAI and UAI close to 40%). During phytoplankton exponential growth phase bacteria show an EAI stability, but there is an increase of UAI with maximal values at the beginning of chlorophyll plateau (52–57%) and higher values of diversity (¯H greater than 4). Phytoplankton mortalities appear to cause an EAI increase and a decrease of both UAI and ¯H (1.50 to 2). Vibrio-like organisms seem to be closely related to this period.