# Three-Year Follow-Up Assessment of Anthropogenic Contamination in the Nichupe Lagoon
## 4 Conclusions  
The results of this study provide an updated reference of the status of the various zones within the lagoon system, impacted by anthropogenic activities and seasonal variations, particularly related to tourism and hydrometeorological events. Although a decrease in nutrient and caffeine concentrations was recorded in 2020 (possibly influenced by reduced tourism activities due to the pandemic and dilution from Tropical Storm Cristobal), the increases observed in 2019 reflect a eutrophication process related to anthropogenic wastewater input. This phenomenon, driven by wastewater discharges and contaminant transport through underground connectivity and water flows, suggests that the system's resilience capacity is being exceeded by the load of nutrients and other contaminants, thereby compromising its functionality and biodiversity [47; 48].  
The findings in this work provide a reference for the current contamination state of the different areas within the lagoon system and demonstrate the presence of anthropogenic wastewater by means of the caffeine tracer, showing that the spatial and temporal variations in the lagoon could result from normal precipitation vs. anomalous precipitations hydrological changes, coupled with the number of tourists in the area.  
Considering this, there is an urgent need to implement wastewater treatment programs and continuous monitoring of key indicators (nutrients, dissolved oxygen, chlorophyll-a, and caffeine) during at least two climatic seasons throughout the system to determine whether the conditions observed in this study are permanent or variable over time. Additionally, daytime monitoring of dissolved oxygen using continuous meters is recommended in each zone as an early warning measure to address the worsening of potential negative effects on the ecosystem and the implications for human health.  
The results of this study showed the relevance of year-by-year monitoring of vulnerable systems such as the NLS, to fully understand the dynamics of human contamination and the changes derived from the hydrological or geological context, which are highly relevant in karstic areas worldwide.  
Conceptualization, J.H.-S.; methodology, J.H.-S., E.L.-C., I.O.-V., E.N.-B., D.M.-E. and C.T.-H.; validation, F.A.-C., K.L.-A., I.O.-V. and E.N.-B.; formal analysis, [PERSON], F.A.-C., [PERSON]-A., E.L.-C., I.O.-V., E.N.-B. and D.M.-E.; investigation, [PERSON]-[PERSON], F.A.-C., E.L.-C., I.O.-V., E.N.-B. and [PERSON]-H.; resources, [PERSON]-[PERSON], F.A.-C.; I.O.-V. and E.N.-B.; data curation, F.A.-C., [PERSON]-A., E.N.-B. and D.M.-E.; writing--original draft preparation, [PERSON]-[PERSON], [PERSON]-C. and [PERSON]-A.; writing--review and editing, F.A.-C., K.L.-A., [PERSON]-C. and [PERSON]; visualization, [PERSON]-C. and [PERSON]-[PERSON]; supervision, [PERSON]-[PERSON], [PERSON]-C. and [PERSON]-H.; project administration, [PERSON]-H.; funding acquisition, [PERSON] and [PERSON]-H. All authors have read and agreed to the published version of the manuscript. Funding Funding for the research was provided by PAIP-UNAM 5000-9146 and Marine Resource Department Cinvestav Merida. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Data is available upon request.  
The authors wish to thank the reviewers for their insightful commentaries that helped improve the quality of the manuscript.  
The authors declare no conflicts of interest.