On each of a 4‐month series of weekly cruises in Kaneohe Bay, Oahu, Hawaii, in vivo chlorophyll a was monitored continuously by fluorometry, and at 8 stations discrete measurements of chlorophyll a (trichromatic method), primary productivity (14C), and nutrients (nitrate and phosphate) were made. The results are compared with similar data collected a decade earlier in the bay to investigate the enrichment effects of increased waste discharge over this period. The south sector of the bay, site of two sewage outfalls, showed the greatest population instability and had the highest concentrations of chlorophyll a, nitrate, and phosphate, as well as the highest primary productivity. Chlorophyll, nutrient concentration, and primary productivity decreased through the transition sector into the north sector of the bay, which is farthest removed from the waste discharge points. The productivity index (mg C fixed hr−1 mg Chl a−1) showed no such south to north differences. A model of a simplified food chain using a hyperbolic relationship between uptake rate and substrate concentration is postulated to explain the dynamics of the plankton community in the bay.