Zooplankton secondary production: main methods, overview and perspectives from Brazilian studies

Since zooplankton is the main route of biomass transfer between producers and consumers, zooplankton secondary production is an important measure to evaluate the flow of matter through the trophic levels in aquatic food chains. Secondary production measures may be employed to characterize the zooplankton functional role and to assess the impacts on ecosystem processes and services. The objectives of this study were: 1- to review the main methods to quantify zooplankton secondary production and 2- to carry out a survey of the studies made in Brazil, identifying their gaps, potentialities and perspectives. We conducted a search of all publications using secondary production measures in Brazilian aquatic environments in different databases ("Web of Science", "Scopus" and "Scielo"). We found that secondary production measures are based on three main approaches: physiological, enzymatic and population dynamics. The main measures of zooplankton secondary production used in freshwater environments are based on recruitment and biomass increase methods while in transitional and marine environments predominate measures based on growth rate. We found 60 publications among scientific articles, thesis and book chapters developed in Brazil. The studies on zooplankton secondary production have grown in recent years, however most publications were carried out in the southeast region, especially in reservoirs with descriptive approaches. Since there is still a lack of basic information on tropical species and environments, it is important to develop new studies focusing on more complex issues, such as aquatic ecosystems functioning, the effects of environmental changes and anthropic impacts on ecosystem processes and the aquatic environments contribution to biogeochemical global cycles.