SCAVIA and BRIAN

Scavia, D. and Eadie, B.J., 1976. The use of measurable coefficients in process formulations -zooplankton grazing. Ecol. Modelling, 2: 315--319. This paper redefines a construct previously used to model phytoplankton--zooplankton interactions in such a way as to permit the use of measurable quantities as construct coefficients. The new construct can use unaltered values of the half-saturation constant for zooplankton grazing on total available food (ks) and the minimum food concentration necessary to stimulate effective feeding (BMIN) reported in the literature. Typical values for these coefficients are 0.1--15 and 0.016--0.19, respectively. Modellers of aquat ic ecosys tems strive to obta in realistic process formulat ions in their models . In developing expressions to mimic func t iona l processes in these models , one should obta in an equa t ion whose coeff icients can be es t imated f r o m ei ther existing l i terature or t rac table l abora to ry and /o r field exper iments . In this way, the cal ibrat ion step in mode l deve lopmen t can be p e r f o r m e d more readily and the assumpt ions sur rounding the convers ion of existing process coeff ic ient values can be kept to a min imum. The purpose of this no te is to redefine a cons t ruc t used for model l ing zoop l ank ton grazing so tha t its coeff ic ients are readily estimable. The original cons t ruc t was developed by O'Neil l et al. (1972) and modified by Bloomfie ld et al. (1973) . I t has been used in various ecosys tem models (Park et al., 1974, 1975) and is descr ibed in detail by Scavia and Park (1976) . The basic equa t ion iCii = CMAXj Wij (B(--BMIN,~) 1 B~., ' :K i + ~ Wi j (B i BMINij)~ (1)