The distribution of phytoplankton and the diversity of environmental conditions for their growth around the South Island, New Zealand, were examined in May 1989 by way of chlorophyllafluorescence profiling in combination with discrete sample analysis of nutrients and particulates, CTD‐profiles, and concurrent satellite images of sea surface temperature (SST). A composite of 7 overlaid SST images from the period of the cruise emphasised the strong north‐south and east‐west gradients in the oceanic environment. Water column sampling coupled with SST imagery was used to examine the frontal structure in Cook Strait, upwelling along the West Coast, gradients across the Solander Trough and through Foveaux Strait, and oceanographic features associated with the Subtropical Convergence off the East Coast and over Chatham Rise. A correlation analysis of the near‐surface water properties showed the zonal relationships between nutrients, nutrient ratios, and temperature, but also underscored the strong local influence of freshwater inputs around the South Island coastline. An analysis of the in vivo fluorescence data revealed large site‐to‐site differences in the fluorescence yield per unit extracted chlorophylla.The yield varied systematically with changes in the physical and biological environment across the Subtropical Convergence.