A size-spectrum zooplankton closure model for ecosystem modelling

A zooplankton closure model is developed by combining the size-based growth and mortality rates and size (biomass) spectrum theory. The new growth rate model, developed based on both Huntley and Boyd [(1984) Food-limited growth of marine zooplankton. Am. Nat., 124, 455-478.] and Hirst and Bunker [(2003) Growth of marine planktonic copepods: Global rates and patterns in relation to chlorophyll a, temperature, and body weight. Limnol. Oceanogr., 48, 1988-2010.], avoids overestimating zooplankton growth at the high temperature and food concentration condition; the mortality rate model developed based on the slope of observed biomass spectra and assimilation efficiency; and the biomass spectrum theory is a conservation equation of biomass fluxes between size classes in terms of growth and mortality The zooplankton closure model is applied to simulate particular organic carbon and mesozooplankton biomass concentrations from 5 January 1999 to 12 July 2007 forced by temperature and chlorophyll, all of which were observed at the Service d'Observation do Frioul du Centre d'Oceanologie de Marseille (SOFCOM) long-term monitoring station in the Gulf of Lions, northwestern Mediterranean Sea. The modelled zooplankton biomass and size spectra imitate the seasonal variations and responses of zooplankton communities to phytoplankton blooms. The carbon fluxes of total grazing, grazing on phytoplankton, feeding on zooplankton and removal from the zooplankton community are analyzed equal to 78, 40, 38 and 14 mg C m(-3) day(-1), respectively This zooplankton closure model is intended to provide a link between lower and higher trophic level models in ecosystem modelling.