Some consequences of distributional heterogeneity of phytoplankton and zooplankton1

Information on the small‐scale distributions of phytoplankton and the developmental stages of the copepod Calanus pacificus was combined with estimates of ingestion and respiration to examine the consequences of distributional heterogeneity on the nutrition of the copepods. During two cruises, in April and June, the average situation was such that the population of copepods in the water above the thermocline could at least meet its metabolic requirement by feeding on all sizes of phytoplankton. Although the rate of ingestion by the population was insufficient to meet its requirement at 25 of the 61 points sampled in April, there was at least one depth at each of the ten stations where the requirement was being met. In June the population was better nourished, on the average, than in April, but at five of the twelve stations there was no depth above the thermocline at which ingestion equalled respiration. The duration of this patchiness will determine its ecological impact.