Materials for plankton modelling: Vertical distribution of Atlantic zooplankton in summer

• Published in: Journal of Plankton Research
• Main Authors: Longhurst, Alan, Williams, Robert
• Format: Text
• Language: English
• Published: Oxford University Press 1979
• Subjects: Articles; North Atlantic
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/1/1/1; https://doi.org/10.1093/plankt/1.1.1

Current versions of plankton production models which allow variability in the vertical plane are based on very slender assumptions about vertical distributions of zooplankton. A late summer LHPR section across the N.E. Atlantic and some spring and early summer LHPR hauls at 59°N indicate some of the details of vertical distribution which seem to be important for model-formulation. It is suggested that a model which is designed to simulate vertical plankton structure in the North Atlantic should cause zooplankton to be distributed during the production period so as to satisfy the following criteria: 60–70% of the biomass must be of carnivores, and 25–75% of all biomass should come to be located within a discrete epiplankton layer within 40 d of the start of the seasonal production: this epiplankton should extend down to 3–4 times the depth of the mixed layer, with its lower limit near the base of the seasonal tbermocline; the epiplankton must extend deeper than the depth of negligible chlorophyll, and 3–4 times deeper than the chorophyll mnTimnm; maximum concentrations of filter-feeders should be located at aboout half the depth of the chlorophyll maximum, and the mmimnm of predators rather deeper; below the epiplankton, biomass should be rather constant down to 1,000 m, be about 15–30 times less abundant than the epiplankton, and should contain discrete layers of interzonal migrants. It is suggested, by reference to FLEX LHPR profiles, that there are important differences between the oceanic plankton and the copepod-dominated spring plankton in the North Sea, which will have important consequences for plankton modelling.