Determination of the trophic state of the Tiscapa lagoon, located in the department of Managua, Nicaragua

Abstract

The Tiscapa Lagoon Natural Reserve is situated in the heart of Managua, just two kilometers away from Lake Xolotlán´s shoreline.  Human activities, notably the introduction of domestic wastewater and solid waste starting in 1980, have primarily impacted this body of water (García Espinoza, 2020). This study evaluated Tiscapa Lagoon´s trophic state based on transparency, chlorophyll-a, and total phosphorus, employing methodologies like the Modified Carlson Trophic State Index (TSI) by Aizaki and the Organization for Economic Cooperation and Development (OECD) Eutrophication Committee model. Water quality sampling was conducted in April, June, August, and December of 2022. Additionally, future scenarios for the lagoon were modeled using Vollenweider´s equation coupled with the OECD index, providing insight into total phosphorus and chlorophyll-a dynamics. The findings reveal a hyper-eutrophic to eutrophic state in the lagoon, indicating a high nutrient presence impacting dissolved oxygen levels an algal bloom, thus compromising water quality. Both continuous and non-continuous input simulations sustained the lagoon in ah hyper-eutrophic state. Simulation of the ideal scenario, reflective a natural condition, showcase an oligotrophic to ultra-oligotrophic state. The study emphasizes the urgent need to tackle nutrient overload and implement remedial measures to restore and safeguard the quality of this crucial water resource in Nicaragua.