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Journal of Plankton Research








A model of the lower trophic levels that consists of a system of coupled ordinary differential equations was developed to investigate the time-dependent behavior of doliolid populations associated with upwelling features on the outer southeastern US continental shelf. Model equations describe the interactions of doliolids with two phytoplankton size fractions, five copepod developmental stages and a detrital pool. Additional equations describe nitrate and ammonia. Model dynamics are based primarily upon data obtained from field and laboratory experiments for southeastern US continental shelf plankton populations. Variations on a reference simulation, which represents average upwelling conditions without doliolids, were carried out to determine the effect of inclusion of doliolids, temperature and nutrient variations, and variations in ambient food concentrations on the basic plankton community structure. These simulations provide a measure of the role of environmental versus biological interactions in structuring the planktonic food web on the southeastern US continental shelf. Simulations show that the copepod population is significantly reduced when doliolids are present. This happens primarily as a result of direct predation of the doliolids on copepod eggs and juveniles as opposed to an increase in competition for phytoplankton, the primary food source. Additional simulations show that the cooler temperatures associated with the newly upwelled water temporarily decrease the growth rates of the doliolids and copepods, bestowing an even greater advantage on the rapidly reproducing doliolids.


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© Oxford University Press 1999.

Original Publication Citation

Haskell, A. G. E., Hofmann, E. E., Paffenhofer, G. A., & Verity, P. G. (1999). Modeling the effects of doliolids on the plankton community structure of the southeastern US continental shelf. Journal of Plankton Research, 21(9), 1725-1752. doi:10.1093/plankt/21.9.1725


0000-0001-6710-4371 (Hofmann)


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