Nutritional Constraints on Zooplankton

Abstract

Aims: This chapter covers main and recent findings in the study of zooplankton nutritional constraints. We will present detailed laboratory studies on the physiological needs of zooplankton regarding food quantity and single elements or biochemicals. In addition, we aim to summarize the findings on the degree and type of nutritional constraints experienced by zooplankton in different seasons and lakes.Main concepts covered: Nutritional constraints are studied via linking zooplankton growth to various concentrations of food of different quality via functional response curves. This work has quantified the role of food quantity limitation for zooplankton growth, as well as identified important food components constraining the quality of zooplankton food such as elements, long-chain poly-unsaturated fatty acids, sterols and amino acids. Further work has shown that zooplankton might be constrained by several food components simultaneously, and that water temperature strongly influences the strength of both quantity and quality constraints.Main methods covered: We explore how controlled laboratory experiments aim at separating the roles of food quantity versus quality constraints in zooplankton, and compare the various approaches on identifying the strength and type of nutritional constraining zooplankton growth in situ. While correlative studies suggest limitation of zooplankton growth by the availability and quality of food, experimental supplementation of laboratory-cultured algae or of lake seston with specific dietary compounds provided strong evidence for both quantity and quality limitation of zooplankton growth.Conclusions: Laboratory studies show that there is a strong potential for both food quantity and quality limitation of zooplankton as well as co-limitation by different quality compounds. Likewise, field studies suggest that limitation of zooplankton growth by both food quantity and food quality occurs frequently in lakes. However, the relative importance of food quantity versus food quality, and especially of the various food quality components has been difficult to identify in situ. Available studies suggest that during the spring season, zooplankton is strongly constrained by temperature and less by food quantity and quality, whereas during summer, zooplankton populations are constrained by both food quantity and quality.