Determinant variables on the isotopic values of particulate organic matter in a neotropical floodplain

Particulate organic matter (POM) is an important energy source for aquatic consumers, understanding its origin and composition is essential for understanding the energetic dynamics of aquatic environments. The aim of this study was to analyze the relationship between POM and phytoplankton (isotopic values and chlorophyll concentration) and abiotic variables during dry and rainy seasons. Sampling was conducted in rivers and lagoons in the floodplain of the Upper Paraná River. We found a greater difference in δ¹³C values of POM between sampling points than between seasons, indicating that the composition of regional sources influences the composition of POM more than dry and rainy seasons. In addition, the concentration of chlorophyll during the dry season was positively correlated with δ¹³C values during that rainy period. Additionally, we found a relationship between factors limiting the growth of phytoplankton and δ¹³C values of POM, such as phosphate ions, indicating that variables that regulate phytoplankton growth tend to influence the composition of POM in river floodplains. Therefore, maintaining the variables that regulate the phytoplankton community is of fundamental importance for the composition of POM, an important energy source in aquatic environments.