Continental aquatic ecosystems, both lentic and lotic, are essential components of the biosphere as they provide ecosystem goods and services that support human life and biodiversity. Water quality and trophic status indices have become fundamental tools for diagnosing and communicating the ecological condition of these ecosystems. The objective of this study was to evaluate the functionality and identify internal processes of phosphorus release and/or retention in the sediments of Castillero Lagoon using the functional trophic vulnerability index (IVT-Ecológico). The index was developed by considering the interrelationship between physicochemical and geochemical elements (pelagic and benthic), incorporating variables that promote phosphorus release as well as those that act as stabilizers or buffers of the system (PBD, P-O, P-Ad+Fe; PO4³-, NOₓ, DO, TSS; pH, CaCO3). The results were compared with a multivariate PCA analysis. An IVT value of 3.77 was determined, classifying the lagoon as a system with phosphorus retention and recycling due to the accumulation of labile phosphorus; however, these processes are weak. The results are consistent with those provided by PCA and the W and IEP indices. These findings confirm that the IVT-Ecológico is a reliable indicator for identifying trophic vulnerabilities with high sensitivity. Therefore, its use is recommended in monitoring programs, eutrophication studies, comparative research, and the management of tropical ecosystems.
