Gross growth efficiencies of protozoan and metazoan zooplankton and their dependence on food concentration, predator‐prey weight ratio, and taxonomic group

Abstract

A comprehensive datasct on the gross growth efficiency (GGE) of planktonic protozoans and metazoans was gathered from the literature in order to (1) identify typical ranges of values, (2) to reexamine the taxon specificity of GGE, and (3) to evaluate the impact of food concentration, predator-prey weight ratio, and temperature on GGE. All taxa (i.e. nano/microAagellates, dinoflagellates, ciliates, rotifers, cladocerans, and copepods) were found to have mean and median GGE of -2O-30%. Contrary to the common practice of using different values of GGE for ciliates and crustaceans, I found that the GGE hardly differed between taxa. Variability within all taxa was high and could only partially be attributed to the independent variables mentioned above. The dependency of GGE on food concentrations was the most reliable relationship identified by multiple regression. Establishing further generalizations regarding the dependency of GGE on other factors was hampered by methodological differences among studies and taxa and the lack of information on other potentially important factors such as the clemental composition of prey items. Future studies of GGE should recognize the importance of these factors.Knowledge of fluxes of matter and energy within ecosystems is a prerequisite for the understanding of food web regulation and of the role that oceans and lakes play in the global carbon cycle (Longhurst 199 1). However, quantifying carbon fluxes reliably in particular ecosystems is hampered by many difficulties. The complexity of aquatic food webs outpaces our capacity to make all the necessary measurements at any one site (Vkzina and Platt 1988). This fact forces ecologists to infer unknown fluxes from those that have been measured. A relative straightforward and therefore common approach is to estimate ingestion rates, Z, of a group of organisms (of a guild) from measured growth rates, G, and a fixed gross growth efficiency, GGE: Z = G/GGE. The crucial ratio GGE (G/Z) is the fraction of prey carbon consumed converted to predator carbon. Despite its importance and abundant use in numerous models and applied studies, e.g. on the estimation of fish yield, the literature on GGE is not well developed and provides no or only a few weak generalizations.Searching the literature of carbon flux modeling, one finds that one generalization in particular has reached modelers' ears: planktonic protozoans are thought to achieve higher GGE than do planktonic metazoans. Modelers are quite aware of high protozoan GGE (sensu Caron et al. 1990a) and usually use protozoan GGE 240% in their models. On the other hand, the conclusion of Calow (1977)-that "Metazoa can achive the best possible levels of efficiency pre- AcknowledgmentsThis study was performed within the Special Collaborative Program (SFB) 248 "Cycling of matter in Lake Constance" supported

Phytoplankton growth, microzooplankton herbivory and community structure in the southeast Bering Sea: insight into the formation and temporal persistence of an Emiliania huxleyi bloom

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Modelling the plankton groups of the deep, peri-alpine Lake Bourget

“…C was set for each heterotroph from the relationship C =GGE/NGE (Straile, 1997), where GGE refers to gross growth e ciency and NGE refers to net growth e ciency. GGE's were taken from Straile (1997) to be 0.40, 0.3 and 0.3 respectively for M, ZH and ZC; and NGE (growth/(growth+metabolic losses)) was estimated to be N GE = Gmax/(Gmax + m + e). p j,k…”

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“…An independent grazing rate can be derived from gross growth rates of 1% of krill mass d -1 measured for northern South Georgia ). Based on a gross growth efficiency of 30% (Straile 1997), the daily ration would be 3.3%. Whether based on a ration of 3.3 or 5%, high concentrations of krill within the east off-shelf region are likely to have a substantial grazing effect on phytoplankton.…”