The phytoplankton community of the Putemun Channel (southern Chile) and its correlation with some environmental variables is analysed in this paper. Samples were collected on a monthly basis from May 1991 to May 1993. A total of 121 phytoplanktonic species were identified. The phytoplankton cell abundance ranged between 3.5 × 104cells/litre and 11.2 × 106cells/litre. The phytoplankton community was characterised by the dominance of diatoms. An inverse relationship between temperature and species diversity was observed. A significant correlation, after excluding tychoplank‐tonic benthic forms, was found between chlorophylla, cell abundances, and temperature. The influence of biotic and abiotic variables on oyster (Ostrea chilensis(Philippi 1845)) growth was analysed. The instantaneous growth rate was found to be positively correlated with both temperature and phytoplankton abundance, whereas significant negative correlation between growth and amount of particulate inorganic matter was found.