Applicability of phytoplankton diversity and trophic state indices as indicators of the eutrophication process in the areas of the Rio Grande branch and Central Body of the Billings reservoir ; Aplicabilidad de los índices de diversidad y estado trófico del fitoplancton como indicadores del proceso de eutrofización en las áreas del brazo del Río Grande y Cuerpo Central del embalse Billings ; Aplicabilidade dos índices de diversidade fitoplanctônica e do estado trófico como indicadores do processo de eutrofização nas áreas do braço do Rio Grande e Corpo Central do reservatório Billings

The phytoplankton structure is influenced by environmental factors, seasonal cycles and trophic degree of the system. The objective of the present study was to identify how the diversity of phytoplankton species responds to environmental factors such as the seasonality and the trophic state of the Billings reservoir, located in the Metropolitan Region of São Paulo (RMSP). Physicochemical and biological variables were analyzed in Central Body (CC) and Rio Grande branch (RG), throughout a seasonal cycle (February to November 2020; n = 6). Phytoplankton density was obtained by counting organisms per mL and the diversity, richness and evenness indices were calculated. The calculation of the trophic state index showed a gradient in the trophic degree, with RG being characterized as mesotrophic and CC as eutrophic. The phytoplankton composition consisted of 138 taxa, 34 of which were recorded exclusively in CC and 33 recorded only in RG. Taxonomic richness, diversity and equitability showed small variation in CC and RG. Phytoplankton abundance varied spatially and temporally. The highest densities were recorded in CC, with the cyanobacteria group being the most representative (contribution of 80%). In RG, in addition to cyanobacteria, a contribution from green algae and diatoms was recorded. Phytoplankton proved to be a sensitive tool for monitoring the dynamics of eutrophication processes and the formation of algal and cyanobacterial blooms. ; La estructura del fitoplancton está influenciada por factores ambientales, ciclos estacionales y el grado de trofeo del sistema. El objetivo del presente estudio fue identificar cómo la diversidad de especies de fitoplancton responde a factores ambientales como la estacionalidad y el estado trófico del embalse Billings, ubicado en la Región Metropolitana de São Paulo (RMSP). Se analizaron variables fisicoquímicas y biológicas en Cuerpo Central (CC) y brazo del Río Grande (RG), a lo largo de un ciclo estacional (febrero a noviembre de 2020; n = 6). La densidad del fitoplancton ...