Dynamic Modeling of the Trophic Status of an Urban Tropical Wetland under ENSO Conditions

The climate variability associated with the ENSO phenomenon has a significant impact on wetlands, affecting the total precipitation input and hydrological flows of these ecosystems. The objective of this paper is to study the trophic status variation of an urban tropical wetland under ENSO conditions, through dynamic modeling. The results suggest an increase in precipitation, by 3.32 times, during the La Nina phase compared to the El Nino phase. Wetland input total phosphorus (TP) concentrations are 1.85 times lower during La Nina. This is probably due to a dilution effect exerted by the increase in surface runoff volumes from the basin. The findings suggest a reduction in wetland hydraulic retention time (HRT) during La Nina (1.33 times) compared to El Nino. This trend causes the TP concentration inside the wetland to decrease, possibly due to an increase in the water volume stored (dilution), and by the exit of this nutrient due to a shorter hydraulic renewal (HRT/La Nina < HRT/El Nino). The occurrence of a high input of TP concentration to the wetland does not necessarily indicate a high trophic status index (TSI). This is because the trophic status of the wetland is possibly more associated with HRT rather than input TP concentration. The trophic status of the wetland during the La Nina tends to be eutrophic. Lastly, under ENSO scenarios, the use of Aizaki's method is suggested, because it considers HRT as a decisive factor for the calculation of wetland trophic status.