Application of morphofunctional models to the microplankton community of the Santos estuarine system for the implementation of bioindicators of disturbances

Abstract

The functioning of aquatic ecosystems, as well as the benefits and services they offer to human populations, depends on maintaining their biological diversity. Thus, in the last decades, the description and understanding of biodiversity and how changes in environmental conditions can drive the succession of species in a determinate ecosystem has become one of the main challenges in science due to current concern about global climate change. Estuarine systems are characterized by transient physical and biological gradients as these environments are influenced in different ways by tidal regimes, freshwater discharge, vertical mixing and turbidity, and by the discharge of nutrients. This complexity of the estuarine environments, as well as the constant and sudden fluctuations, especially of salinity, determine the selection of planktonic species adapted to develop rapid responses to the variations of the predominant water mass in the environment and, therefore, these populations assume ecological, physiological expressions and morphological characteristics. Human activities such as eutrophication, dredging of navigation channels and the introduction of alien species through ballast water from ships may lead to further changes in the structure of the planktonic community, including affecting the biodiversity of the system. Given its importance as a base of trophic networks in aquatic systems, the study of time series of the medium and long duration of the density, biomass and taxonomic composition of phytoplankton is fundamental to understand the effects of these changes on the general planktonic community. Santos estuarine complex receives a high pollutant load from the petrochemical and fertilizer industries and is home to one of the largest ports in Latin America, reinforcing the need for deeper monitoring in the region. Classical monitoring methods based on the variation of chlorophyll biomass or taxonomic composition present limitations on the interpretation of results and relationships with environmental variables. The introduction of methodologies based on morphological and functional groups of plankton such as assembly indexes and biotic indexes of integrity, which integrate biological properties with physical and chemical properties, allow a better evaluation of the state of health of an aquatic ecosystem. The present study intends to establish the bases for the implementation of long-term monitoring programs of the microplankton community based on the application of morphofunctional models with the objective of implementing bioindicators of perturbations in the Santos Estuary System. (AU)