How planktonic microcrustaceans respond to environment and affect ecosystem: a functional trait perspective

Abstract

Functional traits are ecologically relevant characteristics of species. They are relevant to community structuring in face of environmental drivers (response traits) and to ecosystem processes (effect traits). For planktonic microcrustaceans, the link between functional traits and their responses or effects is not always clear. Our objective was to review the literature on linking functional traits to environmental drivers and ecosystem processes for planktonic cladocerans and copepods. Response traits are discussed in four categories: morphological, life history, behavioral, or physiological. Temperature, predation, resources, and stressors are important drivers of morphological and life-history traits. Body size, a morphological trait, is probably the most important trait, because it responds to several environmental characteristics and is correlated with physiological traits and to zooplankton impact on ecosystems functions. In an ecosystem perspective, zooplankton is an important energy link between primary producers and secondary consumers. In trophic webs, it may control phytoplankton biomass and productivity, with consequences for whole lakes. Its influence on carbon, nitrogen, and phosphorus cycles is expected to increase with body size. Other traits may be important, but there is a lack of information. We point out the need of more functional trait research, especially with freshwater copepods and neglected tropical species. For a better understanding of natural systems, an integrative approach of multiple traits with multiple environmental drivers and ecosystem functions is necessary.