The increasing demand for water supply, combined with poor land management around freshwater bodies, has threatened aquatic ecosystems. The Bonfim lake, located in the south of the municipality of Natal (RN, Brazil), is a coastal lake that has been used both as water source and as a site for leisure, with impacts on its water quality that are still little understood. This study aimed to monitor the water quality of the Bonfim lake between 2014 and 2016, and to assess changes in land use and cover in its subwatershed from 1985 to 2023. Sampling was conducted at three points (P1, P2, and P3), assessing key physical, chemical, and biological parameters. No significant differences were observed among the points, except for temperature and transparency, which were slightly higher at P2 and P1, respectively. These findings indicate that the lake is a spatially homogeneous environment, as is typical of well-mixed coastal lakes. Monitoring revealed a trend of increasing chlorophyll-a alongside reductions in total dissolved nitrogen and transparency over time. Publicly available data from the long term Água Azul Program indicated an increase in total phosphorus concentration during the same period, but a decrease in chlorophyll, a result that appears to contradict our findings. These changes coincided with the period (2010- 2020) of dramatic expansion of agriculture and urban areas, loss of natural vegetation, and an episode of El Niño. The results indicate early signs of eutrophication in this important oligotrophic coastal lake starting around a decade ago. Our findings draw attention to the need for continuous water quality monitoring and sustainable management, as the Bonfim lake represents one of the main freshwater sources and one of the few remaining oligotrophic lakes in the state of Rio Grande do Norte. Finally, early detection of the eutrophication trends is essential for watershed management adjustments.
Alves, I.C.C.; El-Robrini, M.; Santos, M.L.S.; Monteiro, S.M.; Barbosa, L.P.F. & Guimarães, J.T.F. 2012. Qualidade das águas superficiais e avaliação do estado trófico do Rio Arari (Ilha de Marajó, norte do Brasil). Acta Amazônica, 42(1), 115 – 124. https://doi.org/10.1590/S0044-59672012000100014.
American Public Health Association (APHA) 1999. Standard Methods of Water and Wastewater. 20ª ed. American Public Health Association, American Water Works Association, Water Environment Federation publication. APHA, Washington D.C.
ANA – Agência Nacional de Águas e Saneamento Básico 2021. Estudo de Alternativas - Ampliação do Sistema - Região Agreste Trairí e Potengi/RN. Retrieved in: https://portal1.snirh.gov.br/arquivos/RIO_TDR_SNIRH/EA_RN_025.pdf
Bem, C.C.; Braga, M.C.B. & Azevedo, J.C.R. 2013. Avaliação do estado trófico de um lago urbano raso. REGA, 10 (1), 41-50.
Bezerra-Neto, J.F. & Pinto-Coelho, R.M. 2002. A morfometria e o estado trófico de um reservatório urbano: lagoa urbano: lagoa do Nado, Belo Horizonte do Nado, Belo Horizonte, Estado de Minas Gerais. Acta Scientiarum Maringá, 24 (2), 285-290.
Brownrigg, DMPfRbR, Minka, TP, Bivand. ttP9cbR 2023. mapproj: Map Projections. R package version 1.2.11. https://CRAN.R-project.org/package=mapproj.
Carmouze, J. 1994. O metabolismo dos ecossistemas aquáticos – Fundamentos teóricos, métodos de estudo e análises químicas. São Paulo: Edgard Blücher, 254 p.
Cunha, M.C.B.; Castro, V.L.L.; Martins, G. & Medeiros, R.A. 2014. Comportamento do nitrato em poços tubulares no entorno da lagoa do Bonfim – Nísia Floresta/RN. XVIII Congresso Brasileiro de Águas Subterrâneas.
Duarte, M.A.C. 1999. Utilização dos Índices do Estado Trófico (IET) e de Qualidade da Água (IQA) na Caracterização Limnológica e Sanitária das Lagoas de Bonfim, Extremoz e Jiqui - RN. Master Thesis. Federal University of Paraiba, p. 156.
Esteves, F.A.; Caliman, A.; Santangelo, J.M.; Guariento, R.D.; Farjalla, V.F. & Bozelli, R.L. 2008. Neotropical coastal lakes: an appraisal of their biodiversity, functionings, threats and conservation management. Brazilian Journal of Biology, 68(4), 967–981. https://doi.org/10.1590/S1519-69842008000500006.
Esteves, F.A. 2011. Fundamentos de Limnologia. 3ª Ed. Editora Interciência. Rio de Janeiro, 826p.
Ganguly, D.; Patra, S.; Muduli, P. R.; Vardhan, K.V.; Abhilash K.R.; Robin, R.S. & Subramanian, B.R. 2015. Influence of nutrient input on the trophic state of a tropical brackish water lake. J. Earth Syst. Sci, 124 (5), 1005–1017. https://doi.org/10.1007/s12040-015-0582-9.
Genovez, J.G.F., Arueira, T.D., Prado, L.A.S., Silva, G.F.L., Marinho, C.C., Fonseca, A.L.S., Minello, M., Zandonadi, D.B., Martins, R.L., Esteves, F.A., & Gripp, A.R. 2024. Sandbar breaching promotes long lasting changes on limnological dynamics along the water column of a tropical coastal lagoon. Acta Limnologica Brasiliensia, 36, e29. https://doi.org/10.1590/S2179-975X10923.
Heberger, M. 2022. Global Watersheds (web application). https://mghydro.com/watersheds.
Istvánovics, V. 2009. Eutrophication of Lakes and Reservoirs. Encyclopedia of Inland Waters, 157–165. https://doi.org/10.1016/B978-012370626-3.00141-1.
Jia, J.; Gao, Y.; Zhou, F.; Shi, K.; Johnes, P. J.; Dungait, J.A.J.; Ma, M. & Lu, Y. 2020. Identifying the main drivers of change of phytoplankton community structure and gross primary productivity in a river-lake system. Journal of Hydrology, 583, 124633. https://doi.org/10.1016/j.jhydrol.2020.124633.
Junger, P.C.; Dantas, F.C.C.; Nobre, R.L.G.; Kosten, S.; Venticinque, E. M.; de Carvalho Araújo, F.; Sarmento, H.; Angelini, R.; Terra, I.; Gaudêncio, A.; They, N.H.; Becker, V.; Cabral., C.R.; Quesado, L.; Carneiro, L.S.; Caliman, A. & Amado, A.M. 2019. Effects of seasonality, trophic state and landscape properties on CO2 saturation in low-latitude lakes and reservoirs. Science of The Total Environment, 664, 283-295. https://doi.org/10.1016/j.scitotenv.2019.01.273.
Kahle, D. & Wickham, H. 2013. ggmap: Spatial Visualization with ggplot2. The R Journal, 5(1), 144-161. http://journal.r-project.org/archive/2013-1/kahlewickham.pdf.
Le Moal, M.; Gascuel-Odoux, C.; Ménesguen, A.; Souchon, Y.; Étrillard, C.; Levain, A.; Moatar, F.; Pannard, A.; Souchu, P.; Lefebvre, A. & Pinay, G. 2019. Eutrophication: A new wine in an old bottle? Science of The Total Environment, 651, 1, 1 – 11. https://doi.org/10.1016/j.scitotenv.2018.09.139.
Mackereth, J.F.H.; Heron, J. & Talling, J.F. 1978. Water analysis: some revised methods for limnologists. Freshwater Biological Association. 36, 121.
Mammides, C., 2020. A global assessment of the human pressure on the world's lakes. Global Environmental Change. 63, 102084. https://doi.org/10.1016/j.gloenvcha.2020.102084.
Marengo, J.A.; Torres, R.R. & Alves, L.M. 2017. Drought in Northeast Brazil—past, present, and future. Theor Appl Climatol 129, 1189–1200. https://doi.org/10.1007/s00704-016-1840-8.
Melo, J.G.; Feitosa, E.C. & Silva, E.R. 2000. Hidrogeologia da Região do Complexo Lagunar do Bonfim/RN. 1st Joint World Congress on Groundwater.
Menezes, R.F.; Andrade, A.S.; Attayde, J.L.; Wanderley, B.M.S. & Amado, A.M. 2025. Reduced CO2 emissions despite higher mineralization rates in reservoirs from drier areas of the tropical semi-arid. Hydrobiologia, 852, 3095–3109. https://doi.org/10.1007/s10750-024-05734-9.
Moritz, S. & Bartz-Beielstein, T. 2017. imputeTS: Time Series Missing Value Imputation in R. The R Journal. 9, (1), 207-218. https://doi.org/10.32614/RJ2017-009.
Nobre, R.L.G.; Caliman, A.; Cabral, C.R.; Araújo, F.C.; Guérin, J.; Dantas, F.C.C.; Quesado, L.B.; Venticinque, E.M.; Guariento, R.D.; Amado, A.M.; Kelly, P.; Vanni, M.J. & Carneiro, L.S. 2020. Precipitation, landscape properties and land use interactively affect water quality of tropical freshwaters. Science of The Total Environment, 716, 137044. https://doi.org/10.1016/j.scitotenv.2020.137044.
Nusch, E.A. & Palme, G. 1975. Biologische methoden für die praxis der gewisseruntersuchung Bestimmung des Chlorophyll a und
Phaeopigmentgehaltes in Oberflachenwasser. GWF-Wasser/Abwass. 116(12), 562-565.
Padisák, J. & Reynolds, C. S. 2003. Shallow lakes: the absolute, the relative, the functional and the pragmatic. Hydrobiologia, 506(1), 1-11.
Patakamuri, S. & O'Brien, N. 2021. modifiedmk: Modified Versions of Mann Kendall and Spearman's Rho Trend Tests. R package version 1.6. https://CRAN.Rproject.org/package=modifiedmk.
Pereira, R.; Guimarães Jr, J.A. & Silva Jr, G.C. 2003. Estado da Arte da Bacia Hidrogeológica do Sistema Lacustre Bonfim-RN, Nordeste do Brasil. Rev. Águas Subterrâneas. 17.
Pohlert, T. 2023. PMCMRplus: Calculate Pairwise Multiple Comparisons of Mean Rank Sums Extended. R package version 1.9.10. https://CRAN.R-project.org/package=PMCMRplus.
R Core Team 2023. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/.
Salonen, K. & Sarvala, J. 1995. Field manual for the determination of chlorophyll a and primary production in the Lake Tanganyika research. FAO/FINNIDA Research for the management of the fisheries on Lake Tanganyika GCP/RAF/271/FIN-FM/18, 14 pp.
Santos, V.C. 2022. Uso e cobertura da terra no sistema lacustre Bonfim: planejamento e manejo ambiental para conservação de recursos hídricos. Undergraduate thesis. Federal University of Rio Grande do Norte, Natal, Brazil, 43p.
Savenije, H.H.G. & Van der Zaag, P. 2008. Integrated water resources management: Concepts and issues. Physics and Chemistry of the Earth, Parts A/B/C, 33(5), 290–297. https://doi.org/10.1016/j.pce.2008.02.003.
Schilling, P.; Powilleit, M. & Uhlig, S. 2006. Chlorophyll a determination: results of an interlaboratory comparison. Practitioner´s report. Journal for Quality, Comparability and Reliability in Chemical Measurements.
Schlesinger, W.H. & Bernhardt, E.S. 2020. Inland Waters. Biogeochemistry, 293–360. https://doi.org/10.1016/B978-0-12-814608-8.00008-6.
Souza, C. M., Jr.; Shimbo, J. Z.; Rosa, M.R.; Parente, L.L.; Alencar, A.A.; Rudorff, B.F.T.; Hasenack, H.; Matsumoto, M.; Ferreira, L.G.; Souza-Filho, P.W.M.; Oliveira, S.W.; Rocha, W.F.; Fonseca, A.V.; Marques, C.B.; Diniz, C.G.; Costa, D.; Monteiro, D.; Rosa, E.R.; Vélez-Martin, E.; Weber, E.J.; Lenti, F.E.B.; Paternost, F.F.; Pareyn, F.G.C.; Siqueira, J.V.; Vieira, J.L.; Ferreira Neto, L.C.; Saraiva, M.M.; Sales, M.H.; Salgado, M.P.G.; Vasconcelos, R.; Galano, S.; Mesquita, V.V. & Azevedo, T. 2020. Reconstructing Three Decades of Land Use and Land Cover Changes in Brazilian Biomes with Landsat Archive and Earth Engine. Remote Sensing, 12(17), 2735. https://doi.org/10.3390/rs12172735.
SUDENE 1990. Dados Pluviométricos Mensais do Nordeste. Recife (Série Pluviométrica, 4).
They, N.H.; Amado, A.M. & Cotner, J.B. 2017. Redfield Ratios in Inland Waters: Higher Biological Control of C:N:P Ratios in Tropical Semi-arid High Water Residence Time Lakes. Front. Microbiol, 8, 1505. https://doi.org/10.3389/fmicb.2017.01505.
Toledo Jr., A.P. 1990. Informe preliminar sobre os estudos para a obtenção de um índice para a avaliação do estado trófico de reservatórios de regiões quentes tropicais. São Paulo, Companhia de Tecnologia de Saneamento Ambiental. 12 p.
Tundisi, J.M. & Matsumura-Tundisi, T. 2008. Limnologia. São Paulo. Oficina de textos.
Von Esperling, E., Ferreira, A. C. S., Gomes, L. N. L. 2008. Comparative eutrophication development in two Brazilian water supply reservoirs with respect to nutrient concentrations and bactéria growth. Destination. 226 (1-3), 169-174. https://doi.org/10.1016/j.desal.2007.02.105.
Wetzel, R.G. 2001. Limnology: lake and river ecosystems. 3rd ed. Academic press. San Diego. USA.
Wickham, H. 2016. ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag New York.
Wickham, H.; Hester, J.; Chang, W. & Bryan, J. 2022. devtools: Tools to Make Developing R Packages Easier. R package version 2.4.4. https://CRAN.Rproject.org/package=devtools.
Xu, F.-L. 2008. Trophic Classification for Lakes. Encyclopedia of Ecology, 3594–3601. https://doi.org/10.1016/B978-008045405-4.00136-1.
Zhou, J., Leavitt, P.R., Zhang, Y., & Qin, B., 2022. Anthropogenic eutrophication of shallow lakes: Is it occasional? Water Research, 221, 118728. https://doi.org/10.1016/j.watres.2022.118728.
Environmental Sciences, Aquatic and Coastal Environments.
BJAST adopts the policy of continuous publication of articles. Therefore, whenever a manuscript is approved for publication, it will be immediately available for reading.
