The Limits to Copepod Growth: Resolving the Malthusian Dilemma

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Zooplankton are the major pathway for carbon transfer to higher trophic levels, and to deeper water and the sediments. Estimates of zooplankton production are critical in understanding how short and long term variations in primary production affect these rates of carbon transfer. Drs. Huntley and Lopez have hypothesized that copepod growth is predictable with first-order precision from habitat temperature alone. If this relationship proves to be robust, we will have a powerful tool for estimating zooplankton production. However, the apparent simplicity of this relation raises major issues about plankton dynamics since it denies the usual assumption that zooplankton are food-limited. These investigators from the Universities of California and Hawaii will investigate the thesis that, at the population level, food limitation of copepods operates mainly through changes in mortality rate. They suggest that there is strong evidence for this in fish populations where density dependence operates on the mortality of the early life stages. Thus, the general solution of the Malthusian dilemma for marine populations is to die young rather than starve later. They will address these key questions in the following ways: - (1) Direct measurements of the generation times of a variety of warm-water copepod species, to fill a critical gap in the database; - (2) Experimental testing of the hypothesis that size-specific predation pressure can compensate for the effects of food-limited growth rate by increasing apparent development rate at the population level.