Further observations on the standing stocks of pelagic organisms confirm the occurrence of approximately equal biomass over logarithmically equal size ranges. A simple theoretical framework is developed that shows that the structural elements of the pelagic ecosystem can be described in terms of the sizes of predator and prey and of the efficiencies of their interactions. In practice this means that if the standing stock at any size range is known, the standing stock at any other size can be estimated, and if the growth rate at this size is known, the production can be estimated. The theory is tested on three fisheries. For the Gulf of Maine and the North Sea, phytoplankton production is estimated from fishery production. For the area off Peru the fishery production is estimated from the plankton production. Key words: pelagic ecosystem, predator–prey relationships, plankton production, marine fisheries, Peru, North Sea, Gulf of Maine

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Euphausia pacifica, Thysanoëssa spinifera, T. raschii, T. longipes (unspined form), and Tessarabrachion oculatus molted at 4- to 6-day intervals at 11 to 15 C. The average dry weight of the molts of the first three species was 5.92–9.39% of the animal's final dry weight, and the organic fraction ranged from 73 to 83% of the dry weight of the molts. The oxygen consumption of E. pacifica at 5, 10, 15, and 20 C was directly proportional to the body weight. The slopes of the regression lines were near unity at all temperatures and the difference between the regression coefficients was not significant statistically. The respiration–temperature relation of E. pacifica suggested its eurythermic character. The Q10 value was 2.21 between 5 and 10 C and increased to 2.55 between 10 and 15 C. The Q10 value apparently did not increase with increase in body size. The upper limit of temperature tolerance for the observed population of E. pacifica was close to 20 C. On the day of molting, oxygen consumption of E. pacifica increased by an average of 34.2%. Feeding decreased on the day before and on the day of molting and increased after molting. At 15 C, a daily food intake of 0.022 mg carbon per milligram dry body weight would be required to match the respiratory loss and the loss of integument during the molt.

The marine chrysophyte Dinobryon balticum (Schzütt) Lemm. was one of the dominant members of the phytoplankton community (1.8×103 cells‐L−1) in June and July in Conception Bay, Newfoundland. Dinobryon balticum colonies were common only in samples from June and July. The cells were concentrated at 5 m (X±SD=1.11±4 × 105 cells.L−1) and at 40 m (3.32±2×104.L−1) depths. Colonies were composed of up to 560 cells with a mean (±SD) colony size of 10 ± 1 cells at 5 m and 40 ± 8 cells at 40 m. Fluorescent latex bead‐uptake experiments conducted with field samples indicated that this marine species was capable of phagotrophy and that twice as many Dinobryon cells were ingesting beads at 40 m than at 5 m, although the ingestion rates for those cells actively ingesting beads were similar at both depths. This chrysophyte was found in association with bacteria‐and nutrient‐rich microhabitats of microaggregates and fecal pellets. The cells and colonies observed in this study appeared to be healthy, as demonstrated by their appearance and their ability to ingest beads.